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I53.» ‘53».— 'm '6 {M II I; I . d’ll I_ THESIS This is to certify that the thesis entitled STRENGTH AND COMPRESSIBILITY OF FRESH AND DECOMPOSING PAPERMILL SLUDGE presented by RICHARD KEITH LOWE has been accepted towards fulfillment of the requirements for M.S. degreein CIVIL ENGINEERING QRWM Major professor Date Mme) m NM 07639 MSU LIBRARIES “ RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. STRENGTH AND COMPRESSIBILITY OF FRESH AND DECOMPOSING PAPERMILL SLUDGE By Richard Keith Lowe A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Civil Engineering 1981 ABSTRACT STRENGTH AND CDMPRESSIBILITY OF FRESH AND DECOMPOSING PAPERMILL SLUDGE By Richard Keith Lowe This study was prompted when a paper mill operating a sludge landfill began experiencing operational problems following the disposal of excess biological solids resulting from secondary treatment processes. Sludge instability, the generation of large amounts of leachate, and difficulty in maneuvering haul equipment on the sludge were among the problems en- countered. A laboratory research program was initiated to determine the physical and engineering properties of a primary and a combined primary and secondary papermill sludge. The effect of decomposition of the or- ganic fraction on sludge strength was also investigated. Physical and engineering properties. including consolidation behavior and shear strength, were measured for fresh sludge samples to determine the effects of the addition of secondary sludge. Decomposition of the combined sludge was accelerated for the laboratory study by the addition of nutrients, in proportions similar to those in a bacterial cell, and seed micro-organisms followed by sample storage at 35°C between tests. The ignition test provided information on the organic content of fresh and partially decomposed samples. Decomposition of the sludge organic fraction reduced the amount and strength of interlocking fibers in the sludge mass. In addition to a reduction in sludge strength, large amounts of gas were generated, the permeability of the sludge was greatly reduced, and sludge volume change increased 25 percent due to 27 percent decomposition. ACKNOWLEDGEMENTS The writer wishes to express his appreciation to Dr. 0. B. Andersland, Professor of Civil Engineering, for the standards he set during the writer's education and for his guidance, encouragement, and patience during this research. Thanks are also due to other members of the guidance committee; Dr. C. E. Cutts, Professor of Civil Engineering and Dr. L. E. Vallejo, Assistant Professor of Civil Engineering. The writer also wishes to express his appreciation to the people at Soil Testing Services of Wisconsin, Inc. for their help in supplying information during preparation of the manuscript. Special thanks are also due my wife, Carol, for typing the manuscript and for her patience during my graduate studies. Thanks are also due to Nekoosa Papers Inc., Port Edwards, Wisconsin, for supplying the sludges and financial support which made this research possible. ii TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ............................................... ii LIST OF TABLES ................................................. v LIST OF FIGURES ................................................ viii LIST OF SYMBOLS ................................................ xii Chapter I. INTRODUCTION ........................................... 1 II. LITERATURE REVIEW ...................................... 3 A. Physical Properties of Papermill Sludge ........... 3 1. Composition ................................... 3 2. Water Content ................................. 4 3 Unit Weight ................................... 6 4 Organic Fraction .............................. 7 5 Specific Gravity .............................. 8 6. Hydrogen Ion Concentration (pH) ............... 8 7. Permeability .................................. 9 B. Stress Deformation Behavior of Papermill Sludge... 9 1 Compressibility ............................... 12 2 Shearing Resistance ........................... 17 C. Decomposition of Sludge Materials ................. 22 1 Decomposition Processes and Observed Field Behavior ...................................... 23 2 Effects on Compressibility .................... 23 3 Decrease in Strength .......................... 26 D. Current Landfill Practices ........................ 29 1 Trafficability and Placement .................. 29 2. Rate and Extent of Landfill Volume Change ..... 31 3. Landfill Stability ............................ 32 III. MATERIALS STUDIED, SAMPLE PREPARATION AND TEST PROCEDURES ............................................. 34 A. Materials Studied ................................. 34 B. Test Procedures and Sample Preparation ............ 35 1. Physical Properties ........................... 35 iii Chapter Page 2. Consolidation Tests ............................ 37 3. Triaxial Testing ............................... 39 4. Anaerobic Decomposition of Papermill Sludge.... 46 IV. EXPERIMENTAL RESULTS .................................... 51 A. Physical Properties ................................ 51 B. Stress-Deformation Behavior of the Sludge .......... 51 1. Compressibility ................................ 52 2. Shear Strength of Fresh Sludge ................. 53 3. Decomposition Effects of Shear Strength ........ 54 V. ANALYSIS AND DISCUSSION OF RESULTS ...................... 83 A. Physical Properties ................................ 83 B. Decomposition Observations ......................... 85 C. Consolidation Characteristics ...................... 87 D. Landfill Stability (shear strength parameters) ..... 97 VI. SUMMARY AND CONCLUSIONS ................................. 108 A. Physical Properties ................................ 108 B. Engineering Properties of the Sludges .............. 108 C. Decomposition Effects on Sludge Properties ......... 110 D. Suggested Field Instrumentation and Monitoring ..... 111 VII. BIBLIOGRAPHY ............................................ 113 VIII. APPENDICES .............................................. 116 A. Physical Properties ................................ 116 B. Preparation of Decomposing Sludge Samples .......... 121 C. Consolidation Test Data ............................ 123 D. Triaxial Test Data ................................. 139 E. Example Stability Analyses ......................... 159 iv >>>>>>m (”h-hank 000W LIST OF TABLES Page Major components of pulp and papermill residues (after Perpich and Zimmerman, 1978) ......................... 5 Permeability values of pulp and papermill residues (after Perpich and Zimmerman, 1978) ......................... 5 Concentration of major elements in a bacterial cell (after McKinney, 1962) ...................................... 49 Physical properties of the papermill sludge ................. 57 Summary of consolidation test results ....................... 58 Summary of triaxial test results ............................ 62 Summary of shear strength parameters ........................ 63 Stability analysis for primary sludge slope using CTU test results (a) for a slope with excess pore pressures (b) for a slope with no excess pore pressures ....................... 102 Summary of stability analyses ............................... 104 Water content of sludge samples ............................. 116 Compacted unit weight of sludge materials ................... 116 Organic content determinations .............................. 116 Specific gravity of sludge materials ........................ 117 pH determinations ........................................... 117 Daily measurement of sludge properties at Nekoosa Papers; 1979 ................................................ 118 Nutrient proportions for decomposing sludge samples ........ 122 Quick consolidation test data, primary sludge, Q-Pl ......... 123 Quick consolidation test data, primary sludge, Q-P2 ......... 125 Conventional consolidation test data, primary sludge, C-P1 ........................................................ 127 V TABLE Page C.4 Single load increment consolidation test data, primary sludge ..................................................... 129 C.5 Quick consolidation test data, combined sludge, Q-CI ....... 131 C.6 Quick consolidation test data, combined sludge, Q-C2 ....... 133 C.7 Conventional consolidation test data, combined sludge, C-Cl ....................................................... 135 C.8 Single load increment consolidation test data, combined sludge ..................................................... 137 0.1 Triaxial test data, primary sludge, CU-Pl .................. 139 0.2 Triaxial test data, primary sludge, CU-P2 .................. 140 0.3 Triaxial test data, primary sludge, CU-P3 .................. 141 0.4 Triaxial test data, primary sludge, CU-P4 .................. 142 0.5 Triaxial test data, combined sludge, CU-Cl ................. 143 0.6 Triaxial test data, combined sludge, CU-C2 ................. 144 0.7 Triaxial test data, combined sludge, CU-C3 ................. 145 0.8 Triaxial test data, primary sludge, CD-Pl .................. 146 0.9 Triaxial test data, primary sludge, C0-P2 .................. 147 0.10 Triaxial test data, combined sludge, co-c1 ................. 148 0.11 Triaxial test data, combined sludge, C0-C2 ................. 149 0.12 Triaxial test data, combined sludge, C0-C3 ................. 150 0.13 Triaxial test data, combined sludge with nutrients, CU-CNl ..................................................... 151 0.14 Triaxial test data, combined sludge with nutrients, CU-CNZ ..................................................... 152 0.15 Triaxial test data, combined sludge with nutrients, CU-CN3 ..................................................... 153 0.16 Triaxial test data, partially decomposed combined sludge, CU-CDI ..................................................... 154 0.17 Triaxial test data, partially decomposed combined sludge, CU-C02 ..................................................... 155 vi TABLE Page 0.18 Triaxial test data, partially decomposed combined sludge, CU-CD3 .............................................. 156 0.19 Triaxial test data, partially decomposed combined sludge, CU-CD4 .............................................. 157 0.20 Triaxial test data, partially decomposed combined sludge, CU-C05 .............................................. 158 E.1 Stability analysis for combined sludge slope using ODD test results (a) for a slope with excess pore pressures (b) for a slope with no excess pore pressures ............... 159 E.2 Stability analysis for primary sludge slope using CID test results (a) for a slope with excess pore pressures (b) for a slope with no excess pore pressures ............... 161 E.3 Stability analysis for combined sludge slope using CID test results (a) for a slope with excess pore pressures (b) for a slope with no excess pore pressures ............... 163 E.4 Stability analysis for decomposing sludge slope using 'CTU test results (a) for a slope with excess pore pressures (b) for a slope with no excess pore pressures ............... 165 vii FIGURE 2.1 2.10 2.11 2.12 2.13 LIST OF FIGURES Vane shear strength versus pH, anaerobic conditions (after Al-Khafaji, 1979) ................................... Changes in permeability with changes in organic content and head (after Laza, 1971) ................................ Void ratio-effective stress relations, undisturbed sludge samples (after Vallee and Andersland, 1974) ......... Compression dial reading versus Logarithm of time (after Vallee and Andersland, 1974) ........................ Comparison of actual and predicted time-settlement curves (after Vallee and Andersland, 1974) ................. Ratio of undrained strength to consolidation pressure versus Percent fiber by volume ............................. Equation and definitions for shear strength theory, effective stress basis ..................................... Fiber (organic) content versus Shear strength parameter'E consolidated undrained and consolidated drained triaxial tests (after Khattak, 1978) ....................... Ratio of decomposed to initial sample height versus Percent decomposition (after Al-Khafaji, 1979) ............. Anaerobic decomposition effects on the coefficient of consolidation (a) Initial organic fraction Xfo = 0.60, (b) Initial organic fraction Xfo = 0.80 (after AI-Khafaji, 1979) ..................................... a... Anaerobic decomposition effects on the coefficient of permeability, intial or anic fraction xfo = 0.80 (after Al-Khafaji, 1979) .................................. Vane shear strength versus Decomposition for three model organic soils (kaolinite and pulp fiber) at a consolidation pressure of 1.14 kPa (after Al-Khafaji, 1979) ......................................... Road construction on mill residue (after Perpich and Zimmerman, 1978) ........................................... viii Page 10 11 13 15 16 19 20 .21 24 25 27 28 3O FIGURE Page 3.1. Fixed ring consolidation unit and sludge sample ........... 38 3.2 Consolidation machine with sample in place ................ 38 3.3 Triaxial sample and mold .................................. 41 3.4 Triaxial test (a) mounting the cylindrical sample, (6) sample in cell prepared for testing ................... 43 3.5 Triaxial test equipment ................................... 44 3.6 Schematic diagram showing sludge solids, before and after partial decomposition (after Al-Khafaji, 1979) ...... 49 4.1 Strain-effective stress relationships, primary sludge ..... 64 4.2 Strain-effective stress relationships, combined sludge.... 65 4.3 Compression dial reading versus Logarithm of time for primary and combined sludges .............................. 66 4.4 Consolidation characteristics of primary and combined sluges (a) coefficient of secondary compression, Cox (b) coefficient of consolidation, cv ...................... 67 4.5 Coefficient of permeability, k, versus Effective consolidation pressure for primary and combined sludges ................................................... 53 4.6 Decomposition effects on the coefficient of consolidation fbr model sludge samples (after Al-Khafaji, 1979) and combined papermill sludges ................................ 69 4.7 Deviator stress versus Axial strain for combined sludge samples at various consolidation pressures ......... 70 4.8 Axial strain versus Obliquity ratio, effective deviator stress. pore pressure and pore pressure coefficient, A, curves for primary sludge sample CU-Pl .................... 71 4.9 Consolidated-undrained triaxial test results for primary sludge samples (a) k failure line (b) final water content (c) undrained strength ............................ 72 4.10 Axial strain versus Obliquity ratio, effective deviator stress, pore pressure and pore pressure coefficient, A, curves for combined primary and secondary sludge sample CU-Cl .............................................. 73 4.11 Consolidated-undrained triaxial test results for com- bined primary and secondary sludge samples (a) kf failure line (b) final water content (c) undrained strength .................................................. 74 ix FIGURE 4.12 4.19 5.1 5.2 5.3 5.4 5.5 Typical results from a consolidated-drained triaxial test on primary sludge sample CD-Pl (a) deviator stress (b) volume change ................................. Consolidated-drained triaxial test results for primary sludge samples ............................................ Typical results from a consolidated-drained triaxial test on combined sludge sample C0-C1 (a) deviator stress (b) volume change .................................. Consolidated-drained triaxial test results fbr combined sludge samples ............................................ Axial strain versus Obliquity ratio, effective deviator stress, pore pressure and pore pressure coefficient, A, for combined sludge with nutrients added, sample CU-CNl... Consolidated-undrained triaxial test results for combined sludge samples with nutrients (a) k failure line (b) final water content (c) undrained strength ....... Axial strain versus Obliquity ratio, effective deviator stress, pore pressure and pore pressure coefficient, A, for partially decomposed combined sludge sample CU-CDl.... Consolidated-undrained triaxial test results fer partially decomposed combined sludge samples (a) kf failure line (b) final water content (c) undrained strength ................................ . ................. pH versus Time of sample storage, storage at 4°C in sealed containers ......................................... (a) 1600 magnification of single fresh pulp fiber (b) 2000 magnification of single pulp fiber after about 27% decomposition ......................................... (a) 5400 magnification of decomposing pulp fiber with bacterial cells (b) 20,000 magnification of bacterial cells attacking pulp fiber ................................ Comparison of strain-effective stress relationships for primary and combined sludges .......................... Settlement predictions for sludge placed in a 40-foot deep pile due to placement of final cover (a) primary sludge (b) combined sludge ................................ Page 75 76 77 78 79 8O 81 82 86 88 89 9O 92 FIGURE Page 5.6 Settlement prediction for a 10-foot thick layer of sludge consolidating under the weight of another 10-foot layer (a) primary sludge (b) combined sludge ........ 95 5.7 Dependence of the angle of internal friction (3') on organic content for several sludge materials ................ 99 5.8 Example cross-section of primary sludge slope with possible failure surface .................................... 100 5.9 Effect of decomposition on deviator stress of combined sludge samples in the CIU test ..................... 106 5.10 Summary of consolidated-undrained triaxial tests, kf lines, effective stress basis ............................ 107 xi mlm-h U'W LIST OF SYMBOLS area; or pore pressure parameter pore pressure parameter at failure primary compressibility of soil skeleton, inZ/lb y intercept, effective stress basis pore pressure coefficient secondary compressibility of soil skeleton, inZ/lb; or slice width compression index coefficient of secondary compression coefficient of consolidation original coefficient of consolidation coefficient of consolidation after ith degree of decomposition cohesion (0’1 - (7'3)/2 = undrained shear strength differential thickness initial void ratio specific gravity consolidating layer thickness original sample height decomposed sample height original field thickness of a peat layer original laboratory thickness of a peat sample field primary compression of a peat layer laboratory primary compression of a peat sample secondary compression xii head of water; or slice height coefficient of permeability original coefficient of permeability coefficient of permeability after ith degree of decomposition line through E, versus a} plots coso‘uL sin&(tanT/Factor of Safety) effective consolidation pressure (€73 + 5731/2 ((7-1 - (7'3)/2 settlement dimensionless time factor time time for primary compression pore pressure pore pressure change sample volume sample volume after consolidation volume change weight ovendry sample weight weight of ash after ignition weight of water weight of solids weight of mineral matter weight of cells produced by decomposition weight of undecomposed organic matter after partial decomposition total weight of organic matter xiii weight of undecomposed organic matter weight of decomposition byproducts water content organic fraction initial organic fraction degree of decomposition organic fraction after ith degree of decomposition cell yield angle of k failure line; or angle between vertical and line connecting center of base of slice and center of failure circle dry unit weight wet unit weight vertical strain effective major principal stress effective minor principal stress consolidation pressure initial or present overburden pressure change in stress viscosity of soil structure, lb-sec/in2 shear strength angle of internal friction xiv CHAPTER I INTRODUCTION During the summer of 1976, Nekoosa Papers, Inc. began operating a sludge landfill for disposal of its primary papermill sludge. Prior to site development, a comprehensive geologic investigation included the installation of a groundwater monitoring system. Site operation proceeded as designed, with sludge placement on a progressive ramp and travel on roadways constructed over the sludge. Confinement dikes pro- vided lateral restraint while a small active filling area was maintained. In the fall of 1977, secondary treatment facilities began producing ex- cess biological solids which were dewatered in conjunction with the primary sludge and the combined sludge was disposed of in the landfill. After introduction of the combined primary and secondary sludge, movement of the sludge pile toward perimeter dikes was noted. The active area of the sludge pile exhibited instability including slough- ing of the sludge pile and drainage of large quantities of leachate from the toe and active face. Disposal in this area was curtailed, while perimeter dike heights were increased several times to confine what ap- peared to be a increasing volume of sloughing sludge and leachate. These problems were blamed on lower consistencies of the combined primary and secondary sludge. The initial intent of this study was to contribute information relative to sludge stability, drainage, trafficability and probable long term landfill performance through a review of available literature, laboratory testing and analysis. In considering long term landfill 1 2 performance, it was decided to include, as part of this study, the effects of possible decomposition of the organic fraction of the sludge material on its stability, settlement and drainage. A review of pertinent literature was initiated in an effort to de- termine if similar problems had occurred at other sludge disposal sites and if corrective measures could be applied to this study site. A laboratory research program included determination of the physical pro- perties of the primary and combined primary and secondary sludge. Engi- neering properties of the sludge materials, including consolidation char- acteristics and shear strength, were evaluated in one dimensional con- solidation tests and triaxial strength tests, respectively. Decomposition of the organic fraction of the combined sludge was accelerated by the addition of nutrients, in proportions similar to those found in an average bacterial cell, and seed micro-organisms. Microbial attack on fibers, including a reduction in length, diameter, and structural integrity, are associated with a reduction in shear strength. Triaxial strength tests provided information on changes in the Sludge compres- sibility and strength due to decomposition. Significant strength reduc- tions and higher volumes of leachate released by decomposing sludges reduce landfill stability and increase the need for internal drainage systems. CHAPTER II LITERATURE REVIEW A. Physical Properties of Papermill Sludge The physical properties of papermill sludges serve as a basis for comparison of different sludge types and give a qualitative indication of their engineering behavior. Some physical properties of interest to the engineer in designing a papermill sludge landfill include com- position, water content, unit weight, organic fraction, specific grav- ity, pH, and permeability. 1. Composition The physical and chemical characteristics of pulp and papermill primary sludges vary widely depending on the type of products produced, source of wood fiber, plant design and efficiencies. The major sludge constituents include: water, noncombustible solids (clay fillers, titan- ium oxide, aluminum hydrate, ferric chloride, and lime) and an organic portion composed of cellulose (wood fibers), starches, dextrins, and trace amounts of other organic compounds. The relative proportions of each of these constituents are influenced to a high degree by the grade of paper produced by the mill. Where the product is heavy paper or board, requiring a low filler content, the resulting sludge will have a high fiber content and will be relatively easy to dewater. Fine paper or heavily coated board requires the use of mineral fillers and coatings which, when lost in processing, lead to a high ash sludge which resists dewatering, due in part to the coating of the cellulose fibers by mineral constitutents. With an increase in number of pulp and paper mills utilizing sec- ondary waste activated treatment systems, the need arises for disposal of the excess biological solids. According to surveys conducted by the National Council of the Paper Industry for Air and Stream Improvement, Inc. (N.C.A,S.I.) in 1975 and 1976, more than 80 percent of the paper mills identified as practicing dewatering of biological solids were doing so in combination with primary sludges. The availability of ade- quate quantities of primary sludge solids and the inability to obtain landfillable or economically combustible cakes of secondary sludge at costs comparable to those incurred in dewatering the combined sludges are given as the main reasons for this practice. Secondary sludges generally require conditioning prior to dewatering in order to achieve satisfactory solids capture efficiencies. Depending on the dewatering system employed, additives such as polymers, lime, flyash, alum and ferric chloride are used as flocculants in conjunction with primary sludges to increase de- watering efficiency. The major components in a number of pulp and paper mill residues are given in Table 2.1. As seen in Table 2.1, the percentage of each consti- tuent may vary widely depending on the particular mill. The significance of these variations is seen in the influence which various constituents have on physical properties and behavior of the sludge residue. 2. Water Content The water content, w, of a soil or sludge is defined as the ratio of the weight of water, WW, to the weight of dry solids, W5, expressed as a percentage, w = (WW/W5)100%. In comparison with mineral soils, organic soils (including papermill sludge) generally have much higher water contents which vary markedly with different mills and also within TABLE 2.1 MAJOR COMPONENTS OF PULP AND PAPER MILL RESIDUES (After Perpich and Zimmerman 1978) Item (dry weight basis unless noted) Range (%) Moisture (% total weight) 60 to 80 Ash 10 to 55 Wood fiber 25 to 90 Biological solids 0 to 25 Lime and ferric chloride 0 to 40 Titanium dioxide 0 to 5 Kaolin (clay) 0 to 52 TABLE 2.2 PERMEABILITY VALUES OF PULP AND PAPER MILL RESIDUES (after Perpich and Zimmerman, 1978) Residue type Ash Permeability (% dry weight) (cm/sec) primary 52 3 x 10'6 primary 20 5 x 10'7 primary/secondary 16 4 x 10'7 primary/secondary 45 3 x 10'5 primary 4O 2 x 10'5 primary 40 1 x 10‘5 loose primary/secondary 40 2 x 10"3 consolidated primary -- 2 x 10'7 (at 500 psf) 6 deposits from a single mill (Gillespie, et al., 1970; Andersland, et al., 1972). Because of the high water content of papermill sludges, some pre- fer to use solids content. The solids content is defined as the ratio of the weight of solids to the wet sample weight expressed as a percentage and is related to the water content by the expression: w(%) = 100 100 (2.1) (2 dry solids - I) In examining primary sludge samples taken from eight different sites representing ages up to 15 years, water contents were found to vary from 740 percent to 46 percent (Gillespie, et al., 1970). The variation in the vertical direction was greater than that in the horizontal direction, but was inconsistent with depth or overburden pressure, indicating that stratification was due to production changes at the mills during the past placement history. The compressibility (volume change) and thus the volume of water expelled, and the shear strength (stability) are both highly dependent on the sludge solids or water content. Sludges with higher water con- tents will experience greater volume change under an applied load. The volume reduction of the sludge is accompanied by a nearly equal volume of leachate released. A sludge of low solids content has little shear strength while the same material at successively higher solids contents will acquire considerable shear strength (Charlie, et al., 1979). 3. Unit Weight The wet unit weight of sludge may be defined as the weight of the sludge-water aggregate per unit volume. The unit weight is influenced by the water content, the unit weight of the solid constituents, and the degree of saturation. The dry unit weight, yd, is determined from the relationship: Yd = Xwet/(l ‘I‘ W) (2.2) where‘Xwet is the total unit weight and w is the water content (dry weight basis). The total unit weight of fresh sludges before dewater— ing may approach that of water (62.4 PCF) while the unit weight of a dewatered sludge cannot exceed that of the solid constituents. Values reported by Andersland, et al., (1972) and Charlie, et al., (1979) indicate that for freshly dewatered primary or combined primary and secondary sludge, the total unit weight was approximately 70 PCF. The materials"unit weight, used in calculating the overburden pressure at various depths in a sludge deposit, is required for settlement and stability calculations. Mineral soils, with much larger unit weights, used in conjunction with sludge for landfill drainage blankets and final cover have a pronounced affect on settlement and stability calculations. 4. Organic Fraction Organic matter includes those sludge components containing carbon with the exception of methane, carbon dioxide, and hydrolysis products of carbon (Eastman, 1978). The most common method for measurement of soil organic content is ignition at high temperature to a constant weight. The weight loss expressed as a percentage of the oven dry sample weight before ignition is taken as the organic fraction. MacFarlane (1969) found that this procedure could be in error by up to 15 percent at higher temperatures, due to loss of surface hydration water from the clay min- erals and thermal decomposition of carbonate. A new method proposed by AleKhafaji and Andersland (1981) recognizes this behavior and uses an ignition temperature of 400°C until a constant weight is obtained. This lower ignition temperature minimizes loss of surface hydration water and 8 allows the organic fraction (Xf) to be calculated within :_1 percent accuracy as: Xf = 1 - 1.02 (Hz/W1) (2.3) where W2 is the weight of ash after ignition and W1 is the oven dry sample weight prior to ignition. 5. Specific Gravity The specific gravity of a papermill sludge can be defined as the ratio of the weight in air of a given volume of sludge solids to the weight in air of an equal volume of distilled water at 4°C. The proce- dure for specific gravity determination follows that outlined in ASTM Designation 0854-72, Accurate determination of the specific gravity is difficult due to large amounts of entrapped air or gas bubbles in the sludge material. Andersland, et al., (1972) reported values for the specific gravity of primary sludge ranging from 1.87 to 2.24 with the average being just slightly greater than 2.0. Specific gravity may be estimated by the proportion of mineral solids and onganic material. Values for high ash sludges may approach the specific gravity of the mineral fraction and can be approximated using a weighted average for the specific grav- ities of the organic and mineral fractions (Al-Khafaji, 1979). 6. Hydrggen Ion Concentration (pH) The hydrogen ion concentration (pH) is a measure of the acidity or alkalinity of a solution. The pH of a papermill sludge is usually of in- terest in studying the effect of the leachate on the groundwater, but it is also of interest due to its influence on the decomposition process. A neutral pH (between 6 and 8) is one of the most important factors in promoting microbiological activity needed for the decomposition process (Al-Khafaji,'r979). The effect of the addition of lime, used as a conditioner in the dewatering process, is that it also raises the pH of the freshly dewa- tered sludge. Few micro-organisms can survive if the pH is above 11. The pH, in addition to influencing decomposition, has been shown to in- fluence vane shear strengths as shown in Figure 2.1. 7. Permeability The coefficient of permeability, k, is a constant of proportional- ity related to the ease with which water passes through a porous medium. Test methods for direct determination of k are described by Bowles (1978). Falling head permeability tests conducted on primary papermill sludge have shown the existence of a threshold gradient below which no flow occurs (Andersland and Laza, 1972). After this threshold gradient was exceeded, large variations in k with the average head of water were observed, especially at higher organic fractions (Figure 2.2). These findings lead to the conclusion that gas bubbles in the sludge substan- tially contribute to reduced leachate flow rates and development of a residual pore water pressure observed in an experimental landfill study (Andersland, et al., 1972). Values of k for papermill sludges have been shown to be dependent on the water (or solids) content, the organic fraction, and additives such as lime (Andersland and Laza, 1972). Some representative values of k for various types of papermill sludge are given in Table 2.2. 8. Stress Deformation Behavior of Papermill Sludge An efficient landfill design requires information on the volume change and stability of papermill sludge in response to stress changes. Vane shear strength, gm/cm2 lO 0 To a 5.8 gm/cm2 E1 {-9 = 11.6 gm/cmg 80 _ A ”E: = 23.3 gm/cm Xf0 = 30% 60 - 40 . 20 - 0 l J 5 l 41 5.0 5.5 6.0 6.5 7.0 7.5 Hydrogen ion concentration (pH) Figure 2.1 Vane shear strength versus pH, anaerobic conditions. (after Al-Khafaji, 1979). Permeability, k x 10'8. cm/sec 11 I 0° 00 o 0 {‘r C 8000 . o 43% organic matter _ o 6000 . o 4000 ' 9 I l g n I ll 5} fl - 0 an 35% organic matter 0 2000 - l a .Q 28% organic matter On AlA AAA AA AAA ; 1 4t. 1 {33. 1 A 0 4O 80 120 160 200 240 280 Average head, h, feet of water Figure 2.2 Changes in permeability with changes in organic content and head (after Laza, 1971). 12 Information on the compressibility and shear strength of papermill sludge are summarized. 1. Compressibility Compression of papermill sludge, when placed in a landfill, results in a decrease in sludge volume accompanied by surface settlements. This volume reduction, involves a time dependent release of leachate and re- sults in more space available for landfilling. Volume change and settlement. Terzaghi's (1943) one-dimensional consolidation theory assumes that volume changes associated with a con- solidating stratum occur only in the vertical direction and the resulting change in surface elevation is termed settlement. For highly compres- sible clays and organic soils (including papermill sludges) this set- tlement includes both primary and secondary compression. A common method of estimating the primary compression, S, for a soil or sludge material involves integration of the equation: 5 =gg 6 dz egg—r535 uddmfi'fiAZ dz (2.5) where Cc is the compression index, e is the initial void ratio, a; is o the effective vertical overburden pressure, ART is the stress increment, and dz is a thin layer summed over the layer thickness H. Equation 2.5 has been found to adequately predict primary settlement in an ex- perimental high ash papermill sludge landfill (Vallee, 1973). One- dimensional laboratory consolidation tests provide parameters required in the use of equation 2.5 (see Figure 2.3 for typical results). Another method of estimating primary compression,l§Hf, in a peat layer of initial thickness Hof involved the expression: of [SH] (2.6) Hol 13 .Amnmfl .mwrpm> Lmummv .mmFaEmm mauspm umnezummvcz .wawgmcomumec mwmcum w>muommmo --omumg vwo> m.m mczmwd EU\mx .a .mgammwgn o.m o.H m.o N ~.o mo.o No.o 1-_ - _du-_- . - _-_qu—q a II; o N NEo\mx em. u on om.m u do 1: m.~ mm.H n 66 m-d NEU\mx nu. u on n . 1 0 cm m I w :1 o.m Hm.H " do H-d O l -d NEU\mx mm. u a llmumnulii we.¢n om .. m.m ew.~ u do m-m NEo\mx om. u on mgzvmuogq mucmcmmmmu mgu co vmmon on [my] mm.e u co 1. o.v [I ofi-m-= dFasam ame=_w gamed Av mm.H u do "N-m on «Fasmm n cmamp Lozop .m xuopn soc» m—nsmm nu :1 ,Au m-m LmAmp Ewan: .m xoo_n Eogw opusmm nu IL m.¢ 01194 PIOA 14 where 13H] is the compression of a laboratory sample of original thick- ness H01 (MacFarlane, 1969). Equation 2.6 was also found to adequately predict surface settlements in an experimental landfill (Vallee, 1973). Secondary (long term) compression is usually linearly continuous with the logarithm of time, proportional to the applied load and layer thickness, and may be estimated on the basis of the equation HS = Hca‘log t/tp (2.7) where H5 is the secondary compression, Co, is the coefficient of the secondary compression and equals the slope of the long term settlement versus log time plot divided by the sample thickness at the beginning of the long term stage (Figure 2.4), t is the field time considered, tp is the estimated field time for primary compression, and H is the thick- ness of the peat layer at time tp. Other methods of estimating total compression (Gibson and Lo, 1961; Wahls, 1962) have been found to yield results in general accord with field observations (Figure 2.5). Consolidation behavior. Time rate of settlement predictions invol- ving primary compression are usually based on Terzaghi's (1943) one-di- mensional consolidation equation given as: gg_ = cv gEg_ (2.8) where u is the excess pore pressure at time t at a distance 2 from the midpoint of a doubly drained stratum, and cv is the coefficient of con- solidation. Solution of equation 2.8 requires the use of tabulated dimensionless factors (Perloff and Baron, 1976) and knowledge of the coefficient of consolidation, c These dimensionless factors are based v. on the results of several consolidation tests, which show that the time (t) required to reach a given degree of consolidation increases in 15 o .3..an 6m5w> 3:3 mew» mo Ecamcmuog mzmcm> ocwvmms mev covmmmcnsou ¢.N we: 0 o l O o [I I, \‘ om + H i .. V d/// a. 83 do .. u 0 o [IAII mm? H OOHK l o / / o o / ~35 n J o./ A58 omm.ov cc omN.o u cm: I o o, Acde\med mfieo.ov cpe\~=p memoo.o u d Nao\mx m.o-e.o ucmsmgocv need a o 24-: 825 I Adv all 0 o . I cmm n 031 II' o o/ o / o 9 Inc 0 o l O O 0 had mom.fiv ea om~.o mmdcxdcgp apasam PapuvcH o Ira $85 u to o Asa mfim.ov :. HNm.o 1 cm: a Acws\med memo.ov =*e\~=c mmfio.o u d I ~5o\mx ~.o-fi.o acmsmgucw wood 0 o ofi-m-= dueaPm A3 0 o o O .— P L b p — p — p — p p p — - b p .. oooH con ooe com oofi on oe om oH o.~ o.e o.~ o.H.n.o e.o ~.o H.o mmpacps .oevh add com com pPBJ [rep uotssaddwog o 0 “But on O N (um VS'Z = U; I) v-01 x “I OH 16 ANNmN.adPPm> Educav mm>L=u acmempuumm1mspu umuupvmgn use Fmagom $0 cow—gmnsou m. N mcamrd 9:6; 65:. ooom cog 2: cc Hfi—qd 4 qd——-fi— nullfiUlnTlfiUIAUlAUllfiu ammo.o new NE 55%: omeodu 2.89:. m .2395... D :PEI DP IOH X mm H ‘\H nP\NF m-oH x Nw.¢1m QP\NE -oH x No. mu 59%: ammo. o.n.>u 3 ES .835 do .28.; B Nefio.o 1 no .=.E\N=P eNmo. o ">6 .NLOdgh a .Pgmz AN gmxf mag: .83: 93 L8 mizu 22533"... 33... O a ___d14 mm cm w; 3 saqou; ‘1uawalaqas 17 proportion to the square of the thickness of the layer (H) (Terzaghi and Peck, 1967), hence the relationship t = 153 (2.9) cv where T is a tabulated dimensionless time factor. The governing factor affecting the time-settlement relation appears to be the selection of a representative value of cv. Vallee (1973) reports average laboratory values of cv to be nearly four times smaller than backfigured field values of cv. Similar results were observed on several peat embankments in British Columbia where it was suggested that the time required for a given degree of consolidation (tfield) be cal- culated as _ 1 tfield ‘ Ho field x tlab (2-10) i ”0 lab where H0 is the initial layer or sample thickness and i is an exponen- tial parameter (generally 1.5 for peat, but may be as high as 2.0) (MacFarlane, 1969; Lea and Brawner, 1963). Leachate generation. Consolidation settlement, involves volume change as pore water is squeezed from the sludge. The amount of ex- pelled water (leachate) will equal the volume change of the sludge less any change in gas volume (Charlie, et al., 1979). 2. Shearing Resistance The components of shearing resistance (cohesion, dilatancy, and friction) are dependent on soil composition (Lambe, 1960) and determine in part the behavior of excavated slopes in these materials and the stability of embankments constructed on them. While freshly dewatered papermill sludges of low solids content possess little strength, the same material consolidated to a higher solids content may acquire 18 considerable strength (Andersland, et al., 1972; Charlie, et al., 1979). Proceeding on the assumption that conventional shear strength theories, used to describe mineral soil behavior, apply to papermill sludge, the undrained and drained strength characteristics are outlined below. Total stress basis. Due to the low permeability of saturated papermill sludges, pore pressures caused by rapid construction on, or excavation in these materials may take several days to dissipate. This may approximate an undrained condition (T= 0 analysis) where the strength, cu = 1/2 ( 0‘1 - cr3)f, may be determined from undrained triaxial tests, unconfined compression tests, or vane shear tests. The results are often expressed as a ratio of undrained shear strength to consolidation pres- sure (cu/p). An interesting result of undrained triaxial tests conduc- ted on a model sludge (pulp fiber and kaolinite) shows the linear depen- dence of cu/p on fiber content (Figure 2.6). Effective stress basis. Since the strength of a saturated soil is not constant but changes with effective stress, drainage (consolidation) occurring during load application increases the effective stress, and thus the soil shear strength. Measurement of pore water pressures during undrained triaxial tests allows determination of the effective stress strength envelope, 73=E+ (CT- u)tan$ (2.11) which is normally tangent to the drained test envelope (Wu, 1976). The terms in equation 2.11 are defined in Figure 2.7. As shown in Figure 2.8, consolidated-undrained (BTU) and consolidated-drained (CID) triaxial tests on fiber-clay soils have given widely differing values for the shear strength parameter T'when compared on an effective stress basis. The unusually high friction angles obtained from the CIU test are due to 19 1.0 F 0 9 _ c) C) 0.8 _ «I’l’ll’sa 0.7 1 1 1 1 1 l 1 1 1 J 0 10 20 30 40 50 60 70 80 90 100 % fiber by volume Figure 2.6 Ratio of undrained strength to consolidation pressure versus Percent fiber by volume(data from Khattak, 1978). 20 Tftoni LL ‘73 d 5' f _ _ x (0"+a'31/2 - (3 —')/2 '00“: I 3 100:43'g- OF 88-4—— (3. + 331/2“ ion a - a (a--1/2 11111;: ° or x= .. tint: I 3 x tan. (iii-agilz-I-x J_= '5 ion 8 = sin I "m 9‘ ion ‘ but ton 5" = sin 6 . E’ 6 tan 3 sin I a = —._.a-— cos 3' Figure 2.7 Equations and definitions for shear strength theory, effective stress basis. Shear strength parameter, I , deg. 21 _______ __A ’7 Brittle behavior --------- Plastic behavior ‘ 100' 'EAU Test (after Charlie, 1975) 80 .11 (_ \ ‘ v 010 Tests 0 (after Charlie, 1975) ‘CTU Tests ETD Tests <> ___ (after Laza, 1971 CIU test, failure at peak value of v stress path. 401- % __V v V V /’ V Consol idated- 20 Drained tests, failure @ 20% strain 1 J l 1 _l 0 20 40 60 80 100 % fiber by volume I— T 1 I 1 ‘ 1 ‘ I ' ' 0 20 40 60 80 100 % fiber by weight Figure 2.8 Fiber (organic) content vs. Shear strength parameter" , consolidated undrained and consolidated drained triaxial tests (after Khattak, 1978). 22 fibers being able to transfer tensile loads across potential failure surfaces. For higher organic fractions, the pore pressure will approach the cell pressure causing the effective minor principal stress ($3) to approach zero. Nevertheless, the high fiber content corresponds to a friction angle (QT) approaching 90 degrees (Andersland and Charlie, 1975; Khattak, 1978). The large friction angles obtained from the undrained triaxial test and the continued increase in stress for strains approach- ing 30 percent have led researchers to question the validity of the test method and seek other definitions of failure. An alternate method for defining failure involves the maximum ratio of shear stress to effective normal stress (maximum obliquity) which results in intermediate 3'values as shown in Figure 2.8 (Andersland, et al., 1981). There is no information available regarding the use of these 3' values for field stability applications. C. Decomposition of Sludge Materials In the past engineers have designed papermill sludge landfills assuming little or no fiber decomposition with greater attention being given to the existing engineering properties and field behavior of these materials as influenced by solids content and organic fractions (Andersland and Charlie, 1975). With the advent of secondary treatment facilities many mills are mixing waste activated sludge with primary sludge before dewatering and landfilling the combined mixture (Miner and Marshall, 1975). Nutrients added during secondary treatment processes to promote growth of 800 removing aerobic bacteria may contain sufficient amounts of nitro- gen and phosphorous to support anaerobic bacterial growth and fiber de- composition (Al-Khafaji, 1979; Charlie, et al., 1979). A review of the 23 processes involved in decomposition and their affects on settlement and stability are discussed below. 1. Decomposition Processes and Observed Field Behavior Decomposition of organic soil components is dependent on the avail- ability of nutrients, moisture, and suitable temperatures. In field de- posits aerobic decomposition generally develops above the water table were sufficient nutrients and oxygen are available. The rate and extent of aerobic decomposition are also influenced by the nutrient and oxygen concentration and by the moisture content, temperature, and pH level. Anaerobic decomposition involves the activity of anaerobic micro- organisms where no oxygen is present; primarily below the ground water table. This process is slower than aerobic decomposition, occurs at lower temperatures, and produces foul odors. The anaerobic micro-organ- isms transform complex organic materials into simpler forms of organic by-products resulting in a decrease in the organic solids fraction while producing carbon dioxide, volatile acids, methane, water, and new bacter- ial cells (Al-Khafaji, 1979). These changes in the sludge can drastically alter its mechanical behavior over a period of time. 2. Effects on Compressibility Decomposition reduces the organic solids volume of an organic soil. The effect of decomposition on settlement characteristics of fiber-clay soils under a constant effective consolidation pressure of 3.42 kPa (34.9 gm/cmz) is shown in Figure 2.9. A decrease in sample height of about 57 percent due to 50 percent decomposition of the organic fraction was observed for a pressure of 3.42 kPa (34.9 gm/cmz). Settlement ver- sus time data collected during load application permitted the evaluation of cv using the Taylor square root of time method. Figure 2.10 shows the 24 .Amumfi .anem;X1p< emuumv cowupmoneoumc ucouemm mzmgo> usury; orgasm anuwcw op ummoaeoumu do ovumm m.~ meamvd Auv cowuvmonEouma ow mm om me oe mm on mm om mm o“ m o !I q u q q u q -q q q u u D L Amax ~¢.mv NEU\em m.¢m u mgammwgn copumuvpomcou Huom u cwumc z\o ~.o $5 1 8x a . . cc vo N om o u x “U o om.o 1 ex Au covuuuee uvcmmeo vauvcH OHIPH ‘146184 11911“! 01 pasodwoaap 01193 25 (a) Xfo = 0.60 11.6 gm/cm2 (1.14 kPa) 34.9 gm/cm2 (3.42 kPa) Decomposition (%) 1.0 x (b)o 80 0.8 f° ' o 0 5c =11.6 gm/cm2 (1.14 kPa) .6 _ - 34.9 gm/cm2 (3.42 kPa) 0.4 p 0.2 - 0 1 1 1 1 g 1 J n - o 5 10 15 20 25 30 ‘—§% 40 45 so Decomposition (%) Figure 2.10 Anaerobic decomposition effects on the coefficient of consolidation. (a) Initial organic fraction Xf0=0.60. (b) Initial organic fraction Xf = 0.80. (after Al-Khafaji, 1979). ° 26 decrease in cv with increasing decomposition. Indirect determination of the coefficient of permeability k, through use of cv in conjunction with other consolidation test data, at various stages of decomposition gave the results shown in Figure 2.11. Based on these results, one would expect decomposition in a paper- mill sludge landfill deposit to result in large surface settlements accompanied by a large volume of leachate draining from the sludge for long periods of time and the production of foul odors due to gas gener- ation. Conditions must be suitable for decomposition if these changes are to OCCUI‘ . 3. Decrease in Strength The short term (no decomposition) stability of papermill sludge as determined from the undrained shear strength appears to be highly depen- dent on the solids content or consolidation pressure (Charlie, et al., 1979) and fiber size and content. Disintegration of fibers in papermill sludge, as a result of decomposition, decreases the reinforcement due to interlocking fibers leading to a reduction in undrained shear strength. The increased compression resulting from decomposition of organic solids would tend to counteract this decrease in strength (Charlie, et al., 1979). Miniature vane shear tests performed on fiber-clay soils at various stages of decomposition under a common consolidation pressure yielded results shown in Figure 2.12. Significant decreases in vane shear strength would have serious implications relative to the stability of papermill sludge landfill deposits experiencing small amounts of decom- position. 27 Average curve a"; = 4.8->11.6--23.3-*-34.9 gm/cm2 1. (0.47->1.13--2.28.-3.42 kPa) 0.8 ki 0.6 k° 0.4 0.2 0 1 1 1 1 1 4 0 10 20 30 40 50 60 Decomposition (%) Figure 2.11 Anaerobic decomposition effects on the coefficient of permeability, initial organic fraction Xfo=0.80. (after Al-Khafaji, 1979). Vane shear strength, kPa 28 ansolidation pressure OE=1.14 kPa Initial organic content 80% (by weight) 60% f 30,1 / 2 1- 1 _ ‘A I 7.....JEL-\ a 0 1 l J l l l l 1 O 5 10 15 20 25 30 35 40 45 Decomposition (%) Figure 2.12 Vane shear strength versus Decomposition for three model organic soils (kaolinite and pulp fiber) at a consolidation pressure of 1.14 kPa (after Al-Khafaji,1979). 29 0. Current Landfill Practices The pulp and paper industry generates large quantities of waste effluent, of which a portion is recovered as settled solids requiring an economical and environmentally sound method of disposal. After pri- mary settling, many mills further treat their effluent by chemical and biological means resulting in the generation of excess biological solids which also require disposal. At the present time the most widely prac- ticed method of disposal is'a solid waste landfill site designed and li- censed to accept papermill waste. Since dewatering processes are normally continuous operations which generate up to 400 cubic yards of residue per day, transportation costs require the landfill site be located near the dewatering plant. Consid- erations for the proper geologic setting, determined from studies of the soil profile, bedrock geology, hydrogeology, and surface drainage char- acteristics, have been outlined by Perpich (1976). Two methods of landfill operation, which have received favorable response from licensing agencies, are forming the landfilled sludge into a large progressive ramp utilizing small containment dikes for leachate control or a cellular type construction with dikes used for lateral con- finement of the residue. The latter method, in many cases, uses vertical lifts of 10 to 20 feet separated by horizontal sand layers to promote drainage. Specific methods of landfill operation and their perfor- mance are outlined below. 1. Trafficability and Placement Freshly dewatered pulp and papermill residues are usually of such a soft consistency that they will not support vehicles other than light- weight, wide-tracked bulldozers. Performance studies at a landfill 30 operated by Nekoosa Papers, Inc. indicated that a small dozer with stand- ard tracks encountered considerable difficulty when maneuvering on the sludge outside the progressive ramp roadway area. Experience at a land- fill in Rumford, Maine, operated by the Boise Cascade Paper Group, which disposes of sludge very similar to the combined sludge generated by Nekoosa Papers, Inc., has indicated that a wide-track muskeg dozer was very successful in spreading the landfilled sludge (Charlie, et al., 1979). In the progressive ramp type construction a minimum amount of dike construction is required, but transporting the sludge to the small active area of the pile necessitates construction of haul roads on the sludge material in many cases. One method of road construction which has been found successful at a number of sites, shown in Figure 2.13, uses mater- ials readily available at most papermills. In a cellular type construc- tion, sand dikes constructed in some convenient geometric from usually serve as haul roads with the sludge being dumped into the cell and spread by a dozer or muskeg tractor. aaxvl=ffiiiffH cin-ers;5;3gga.,,u, ‘ I \ /\ . '. .. ‘ "Ox ':".‘ “5 waft/«19% ' ar Q’QKZVKW/Oq‘ drier felt «N .1“ Mill residue Figure 2.13 Road construction on mill residue (after Perpich and Zimmerman, 1978). 31 Sludges of lower consistency (low solids content) will tend to flow at flat angles and may require lateral confinement provided by a cell- ular type of construction, whereas for higher consistency sludges, dis- posal in a large ramped pile may be more economical. In a landfill operated by the Boise Cascade Paper Group in Rumford, Maine, a large active area was maintained with the sludge being spread by a muskeg dozer in horizontal layers. This method of operation was con- veniently used with horizontal sand drainage blankets between lifts of sludge. Effectiveness of this mode of operation is dependent to a large degree on the type of equipment used in spreading the sludge and its maneuverability. If equipment spreading the sludge can effectively move the sludge away from haul roads or sand dikes, the distance between dikes can be increased requiring a much smaller volume of sand for berm con- struction, thus maximizing the space available for filling per acre of land. 2. Rate and Extent of Landfill Volume Change As sludge accumulates in a landfill disposal site, the material near the bottom of the landfill consolidates under the pressure of the overlying material. This densification results in additional volume available for landfilling. The engineer must estimate this volume change when predicting the life of a landfill. The long term deforma- tion must be considered when shaping final contours so that surface drainage will be maintained for the life of the landfill (Perpich, 1976). Consolidation tests performed on representative fresh sludge samples are useful in predicting the volume change expected under landfill con- ditions. The pore water drainage during consolidation (roughly equal to the sample volume change) is useful in estimating the amount of leachate 32 expelled from the landfill. This pore water drainage will occur gradually over the life of the landfill and also for several years after filling to completion. Methods for estimating the volume of leachate expelled from a landfill, as a function of time, have been given by Charlie, et al., (1979). Leachate generation rates will be useful in waste treat- ment volume estimates and in evaluating the environmental impact of the site. Data on leachate generation rates, rainfall, runoff, and evapo- transpiration may be used in conjunction with infilitration rates of the natural subsoils to estimate leachate dilution and contamination poten- tial. 3. Landfill Stability Consolidation, in addition to decreasing the sludge volume also enhances the material stability. Assuming that papermill sludges behave in accordance with the Mohr-Coulomb failure theory,increased overburden pressure and consolidation will increase the sludge shear strength, pro- vided pore water pressures are allowed to dissipate. The undrained (short term) strength of primary and combined sludges appears to be re- lated to the solids and organic content (Charlie, et al., 1979). Many existing papermill sludge landfills, without drainage systems, retain low solid contents and very low shear strength and stability of both primary and combined primary and secondary sludge deposites. A case study at the Boise Cascade Papermill in Rumford, Maine, describes problems identical to those experienced at the Nekoosa Papers, Inc. landfill in Saratoga, Wisconsin. Large quantities of leachate draining from the sludge pile was followed by sloughing of the sludge deposit toward the low containment dikes. Low slope angles were observed. The instability was attributed to the low sludge solids content, low shear 33 strength, and additional factors including steep subgrade and possible fiber decomposition. Modification of the operational plan included place- ment of a 12 inch thick blanket drain over the existing subgrade with underdrain pipes for collection of leachate. Sludge lifts 10 feet thick were separated by drainage blankets including underdrain and collector pipes. This construction method proved successful for approximately 16 months, after which, sludge lift thicknesses were increased to 20 feet without difficulty. It was estimated that after the sludge consolidated, the deposit would be stable at slopes steeper than 45 degrees (Charlie, et al., 1979). The large volume of sand required to construct the granular drainage layers, the cost of the collection pipe, and the need for construction of haul roads over the sludge increased the operating costs. However, the additional consolidation resulted in nearly tripling the site capa- city, increased stability, and provided a positive method for leachate collection. Where site preparation costs are high (i.e., in the case of clay liners or extensive networks of leachate collector pipes) the bene- fit from the additional consolidation is an increase in stability, which in turn allows increased sludge volumes to be stored per acre of land. CHAPTER III MATERIALS STUDIED, SAMPLE PREPARATION, AND TEST PROCEDURES A. Materials Studied The sludge materials used in this study were obtained from Nekoosa Papers, Inc. Water Quality Center in Saratoga, Wisconsin. Samples were obtained immediately after being dewatered by a vacuum filtration sys- tem. Small amounts of sludge were obtained over a period of time (approximately 60 minutes) and combined to form a larger more represen- tative sample. The samples were stored in air tight bags at about 40°F (4°C) prior to laboratory testing. Two samples types were collected; an untreated primary sludge and the typical sludge produced at the plant, a combined primary and secondary sludge conditioned with polymer and lime. Neither of these sludges fit the definition of a high ash sludge as given by Gillespie, et al., (1970). As indicated by their respective organic contents and visual appearance, both of these sludges would be considered highly fibrous. An attempt was made to obtain samples of combined sludge representative of the ma- terial deposited in the landfill, while primary sludge samples were ob- tained for comparison purposes. Both the primary and combined primary and secondary sludge materials were similar in color to wet brown cardboard. Visual examination of both sludges revealed pieces of bark up to an inch in length, numerous wood chips, and measurable fibers averaging 6 millimeters in length. Both sludges contained fine filler materials too small to be visually identified. The primary sludge had a higher proportion of fiber and wood 34 35 chips than did the combined sludge. The primary sludge averaged 27.0 percent solids (270 percent water content) of which approximately 49 percent was organic compared to the combined sludge which was of a sof- ter consistency, averaging 23.9 percent solids (318 percent water content) with an organic fraction equal to 58 percent. The organic fraction of the primary sludge was composed primarily of bark, wood chips, and cell- ulose fiber. The organic fraction of the combined sludge contains the organic material contributed by the primary sludge and nearly all the biological solids from the secondary sludge. A summary of the sludge physical properties is given in Table 4.1. 8. Test Procedures and Sample Preparation Equipment and test procedures used in evaluating the physical pro- perties and stress deformation characteristics of the papermill sludges are given in this section. Standard test procedures are referenced where applicable, with deviations from procedure and special methods of sample preparation described in greater detail. 1. Physical Properties Information on the physical properties of papermill sludges are useful in providing a qualitative evaluation of their field behavior. Water content, unit weight, organic fraction, specific gravity, and pH are considered in the following sections. Water content. The water content of a soil or sludge, which is the ratio of the weight of water to the weight of dry soil or sludge in the sample, was determined by drying at a temperature of 105°C. Details outlining the test procedure are given in ASTM 02216-71. Since the water content of a papermill sludge is usually very high, some prefer to use solids content as a basis for comparison. A simple conversion from 36 water content to solids content was given by equation 2.1. Unit weight. The unit weight or density of a sludge material is defined as the weight of the sludge material per unit volume. The test procedure involved careful packing of the sludge into a container of known volume (1/10 ft3) and weighing to determine the quantity of sludge contained in the bucket. The sludge was placed in five equal lifts and kneaded by hand to eliminate air pockets. Care was taken to avoid any water loss from the sample during placement of the top layer. The measured unit weights of the sludge materials are given in Table 4.1. Organic content. The procedure for determining the organic frac- tion of a soil, or papermill sludge has been given by ASTM 02974-71. This method involves firing an oven dried sample at 550°C, which results in dehydration of the clay minerals and can lead to errors of up to 15 percent (MacFarlane, 1969; Al-Khafaji, 1979). Al-Khafaji (1979) tested kaolinite and fiber samples at various temperatures for different burn- ing durations and found that ignition at 400°C would eliminate much of the error due to loss of surface hydration water. The organic fraction may be calculated by use of equation 2.3. The correction coefficient, 1.02, accounts for dehydration of the mineral fraction at a temperature of 400°C. Al-Khafaji (1979) has shown that this method is accurate to within :1 percent for fiber-clay mixtures. This method was used for determination of the organic fraction of the sludge materials used in this study. Specific gravity. The procedure given by Bowles (1978) was used for determination of the sludge specific gravity. The oven dry sample weight was determined after the test. Boiled distilled water was used as the displacement medium. To help de—air the sample a vacuum was 37 applied. Use of the vacuum for more than a few hours had little affect on the results obtained. Three trials were performed on each sludge type with variations between tests being 0.01 or less. Hydrogen ion concentration. The pH of the sludge material was determined with a Beckman pH meter on samples of leachate squeezed from the fresh sludge. 2. Consolidation Tests The consolidation test provides information concerning the amount and rate of volume change of a soil or sludge sample under load. An explanation and recommended test procedure for conventional consolida- tion tests is given by Bowles (1978). This section describes the method of sample preparation, equipment, and test procedures utilized for the various types of consolidation tests performed. Sample preparation. Consolidation test specimens were prepared by placing the sludge material into the consolidometer ring by hand in 4 layers approximately one half centimeter in thickness. The sludge was kneaded into the ring to minimize void space with care being taken to avoid water loss from the sample. The sample top and bottom were leveled so as to conform to the inner dimensions of the ring (2.5 inch diameter by 0.75 inch high). The specimen and ring were then weighed, permitting calculation of the initial sample weight and density. The sample and ring were then placed on a saturated porous stone in the cell container shown in Figure 3.1. Drainage was allowed through the sample top and bottom by porous stones attached to the loading pad and base. The assem- bly was then placed in the Wykeham Farrance consolidometer (Figure 3.2) used for earlier studies on soft sludge materials (Vallee, 1973). Consolidation test methods. The procedure followed for 38 .mom—n cw opasmm mmusz cur: wcwcums cowpmuwromcoo N.m weamwd .mFaEmw mmuzrm use pen: :owumumpomzoo ace; vexed H.m beamed 39 consolidation tests is the same as that given by Bowles (1978) with minor changes. Except for the final load increment, a load increment ratio (ZSP/P) of one was used with loads of 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, 6.4, and 10.0 kg/cm2 being applied. Settlement versus time data was recorded for each load increment with successive loads applied at 24 hour inter- vals. When loads were left on for this length of time an appreciable amount of secondary compression was included (Figure 2.4). MacFarlane (1969) lists an alternate method of load application which largely elimi- nates the effects of secondary compression and yields a more well de- fined e-log p curve. In this method, successive load increments (same as listed above) were applied at the end of primary compression as determined from Taylor square root of time plots. A disadvantage of this method is that no straight line (long term compression) segment is obtained on log time versus settlement plots, which makes evaluation of cV and CO1 difficult. Another test procedure proposed by MacFarlane (1969), called single increment tests, involves application of the anticipated field load in one increment. Several loads, similar to those expected in the land- fill, were applied to duplicate samples for a period of 24 hours or un- til a straight line portion was easily identified on a settlement versus log time plot. Results of this test method were used in conjunction with equation 2.6 and 2.10 to estimate the magnitude and rate of com- pression. At the end of each of these tests samples were weighed prior to and after ovendrying to determine the final water content and sludge dry weight. 3. Triaxial Testing The triaxial test provides information on the shear strength and deformation characteristics of soil or papermill sludge. The 40 consolidated-undrained (CIU) test was used to evaluate the undrained shearing resistance of the sludge material. Measurement of pore water pressures generated during application of the axial stress allowed eval- uation of the shear strength parameters on an effective stress basis. The consolidated-drained (CID) test was performed at a slow rate allowing pore pressures to dissipate so that the applied total stresses were equal to effective stresses and the shear strength parameters ob- tained were also on an effective stress basis. Procedures used in preparing triaxial test specimens, a descrip- tion of the equipment and its use are considered in the following sec- tions. Procedures used were similar to those outlined by Bishop and Henkel (1962) and Bowles (1978). Sample preparation. Conventional triaxial test specimens, described by Bishop and Henkel (1962), were 3 inches long by 1} inches in diameter. Preliminary tests indicated the volume reduction of this sample size to be nearly 50 percent under a consolidation pressure of 2.5 kg/cmz. Due to these large volume changes, it was decided to use larger samples (4 inches long by 2 inches in diameter) for the testing program. Samples were prepared by kneading the sludge, by hand, into a cylindrical mold while taking care to fill all voids and maintain the original water con- tent of the sample (Figure 3.3). The top of the sample was then leveled off perpendicular to the sample axis and the mold disassembled by pulling its sides directly away from the sample to avoid smearing of the sides. The sample was weighed and dimensions noted after which saturated por- ous stones were placed on the sample ends. Next moist filter paper side drains (Bishop and Henkel, 1962) were wrapped around the sample and por- ous stones. The sample was then mounted in the triaxial cell, and with the loading cap in place, the entire assembly was enclosed in two 41 Figure 3.3 Triaxial sample and mold. 42 watertight membranes (Figure 3.4). Triaxial equipment. The triaxial apparatus shown schematically in Figure 3.5 includes the following equipment: 1) a self-compensating mercury pressure system, 2) a triaxial cell, and 3) a pore pressure measuring system. The self compensating mercury pressure system allows cell pressures to be maintained accurately over long periods of time. The conventional triaxial cell (Bishop and Henkel, 1962) was modified to allow 4 inch long by 2 inch diameter samples to be tested and to permit electronic measurement of the load from within the cell (Figure 3.4). The pore pressure measuring unit connects the bottom of the sample to a pressure gauge through a mercury U-tube. Adjusting the level of the mercury with the pressure control cylinder permitted measurement of the pore pressures developed during load application under undrained test conditions. Consolidated-undrained triaxial test. After the test specimens were mounted in the cell, the cell pressure was slowly brought to the desired consolidation pressure. After a short period of time the drain- age line connecting the sample to a calibrated burette was opened to begin the consolidation process and sample drainage was recorded at given times. Time for the consolidation phase of the test varied depen- ding on the sample composition, but was continued until the straight ‘hne1(long term) portion of the volume change versus square root of time curve became well defined, after which, the drainage line was closed. To increase the degree of saturation, a back-pressure was next applied to the sample by increasing the pore water pressure simultaneously with the cell pressure in order to maintain a constant effective consolida- tion pressure. The magnitude of the back pressure varied, but 2.5 kg/cm2 43 umemnmgn Prmu cw w—QEmm Any w—nEmm 3V .mcwummu Low Fmomcncwpxo on» ocmucsoz Amv “mop pmmxomeh ¢.m mezmmd 44 .pcmsmeammms meammme econ Low vogums FF: Focucou m mama Xezoemz .ucmenmscm “we“ Pmmxmmeh m.m mezawd a z E moamm meammmgm mupmcsmk‘ .poeucou mcammmca xgzuems mappmmcmaeou1mpmm Aev 4%, cape: A.u.>.av daze anPXdFd.1 .PFdd Pawxameh Adv Pocucou :meum nocwz umzoumm mpaEmm Aeaugmz g Laue: / Loan: 1 cowpuzm mmamm meammmgm mcwgam Ema 45 was usually found adequate to give full saturation in the primary sludge samples and 3.5 kg/cm2 was required for the combined sludge samples. This back-pressure was maintained overnight (approximately 16 hours). The pore pressure parameter, 8, was next determined by increasing the cell pressure by a small increment (0.2 kg/cmz) and measuring the pore pressure response, with 8 calculated as follows: 8 = Au/Aag (3.1) The back-pressure and cell pressure were then returned to their initial values and after the sample returned to equilibrium, application of the 3 deviator stress was begun. A deformation rate of 2.5 x 10' inches per minute (6.5 x 10'3 cm/min) was utilized in the research program based on experimental work performed by Laza (1971). This strain rate was found to allow excess pore pressures developed during load application to be- come reasonably equally distributed throughout the sample. During the test, data on axial pressure, axial deformation, and pore pressures were recorded. All tests were carried to at least 20 percent axial strain after which samples were removed from the cell and weighed prior to and after oven drying to determine the final water content. Consolidated-drained triaxial test. The procedure for sample pre- paration and consolidation of drained test specimens was the same as that in the undrained test. After consolidation was completed, application of the axial stress began. The rate of deformation was determined from volume change versus time data recorded during the consolidation phase of the test (Bishop and Henkel.1962). The rate of deformation calculated by this method depends on the anticipated failure strain. For this study the time to failure was calculated with a deformation of 20 per- cent axial strain taken as failure. The rate of deformation varied with 5 sludge type and consolidation pressure, from 8.6x10' inches per minute 46 to 2.05x10'4 inches per minute (2.03x10'4 cm/min to 5.21x10'4 cm/min, respectively). The corresponding time to failure varied from 121 hours to 50 hours. During testing the drainage line connecting the sample and burette was left open and the sample drainage, axial deformation, and load were recorded up to 20 percent axial deformation. The sample was then removed from the cell and the final water content determined. 4. Anaerobic Decomposition of Papermill Sludge In order to investigate the effect of fiber breakdown on the undrained shear strength of the combined primary and secondary sludge used in this research program, samples were allowed to decompose anaerobically. Nutrients added to the samples, environmental control, and preparation of decomposed samples for use in the triaxial test are described in the following sections. Sample preparation, nutrientpproportions and seeding material. Although the combined primary and secondary papermill sludge used in the research program may have contained sufficient nutrients to promote de- composition by itself, time restraints made it desirable to aid the decomposition process by providing a favorable environment and supply- ;ing nutrients known to enhance microbial activity. A municipal sludge obtained from an anaerobic digester served as the micro-organism seed source used to initiate the anaerobic decomposition process. The amount of seeding material used was approximately 0.3 percent of the total dry sample weight. To continue to reproduce and thus bring about decomposi- tion, the micro—organisms must have a minimum supply of the elements of which they are composed (Table 3.1). The approximate empirical fomula- tion of a bacterial cell (McKinney, 1962) given as C5H702N served as a guide in selection of nutrient quantities. Pulp fiber contributed by 47 the primary sludge and bacteria from the secondary sludge supplied the carbon. Ammonium chloride (NH4Cl) was used to supply the nitrogen. Other nutrients found in bacterial cells and their source compounds included KZHPO4 for phosphorous and potassium, MgSO4 for magnesium, CaCl2 for calcium, and FeCl3 for iron. A summary of the calculations used to determine the exact quantities of the compounds to give the desired amounts of nutrients are given Appendix B. The compounds were introduced into the sample by first dissolving in distilled water and thoroughly mixing with 4500 grams (wet weight) of the combined papermill sludge. The material was then transferred into plastic lined containers with small amounts of the seeding material stirred in during filling in an effort to minimize the exposure of the anaerobic micro-organisms to the atmosphere. Enough distilled water was added to allow thorough mixing of the materials. The containers were then covered and trans- ferred to a constant temperature environment. Environmental control. To allow the micro-organisms to metabolize at a near optimum rate, samples were stored in an incubator at a temper- ature of 35°C. The decomposition process is known to produce volatile acids, and if allowed to go unchecked, may depress the pH below 6, thus eliminating the methane producing bacteria. Hence, based on previous research (Al-Khafaji, 1979), 5.6 percent by weight of sodium bicarbonate was added to the sample in an effort to maintain a neutral pH. Decbmposition measurement. Decomposition in organic soils involves the breakdown of complex organic materials into more stable humus pro- ducts and conversion into simpler organic materials used to build bac- terial cells. The ignition test used for measurement of soil organic content does not distinguish between undecomposed organic matter and 48 micro-organisms formed during decomposition, hence it under estimates the degree of decomposition. A schematic diagram illustrating the makeup of the typical organic soil before and after partial decomposition is shown in Figure 3.6. Attempts to separate the micro-organism cell content from the decomposed organic content have proven difficult. The degree of decomposition is given by Al-Khafaji (1979) as xdi =13), [1- xf, Mm] (3.2) l'xfi _I where y is the cell yield, Xf0 and xfi are the initial and final organic fractions determined from equation 2.1 and xdi is the degree of decom- position. The cell yield, y, is a biomass error term which has been very difficult to determine accurately, but is thought to range from 0.05 to 0.2 for soils undergoing anaerobic decomposition (Al-Khafaji, 1979). Due to the uncertainty involved in the determination of the cell yield, it was assumed equal to zero. This same assumption was made in obtaining the percent decomposition shown in Figures 2.9 - 2.12. Triaxial test samples. The magnitude of decomposition in the de- composing samples was monitored by ignition of small samples as des- cribed earlier. When 26.6 percent decomposition was reached, a portion of the samples were transferred from the incubator to a refrigerator in an effort to retard further decomposition. The sample was then spread in pans and air dried to a consistency which would allow molding of tri- axial test specimens. A portion of the dried material was then used for preparation of the triaxial test specimens described in section 3. In order to measure any possible affect of the nutrients and seed- ing material on the strength of the undecomposed sludge, a portion of 49 TABLE 3.1 CONCENTRATION OF MAJOR ELEMENTS IN A BACTERIAL CELL (after McKinney, 1962) Element Concentration Percent Carbon 49.0 Hydrogen 6.0 Oxygen 27.0 Nitrogen 11.0 Phosphorous 2.5 Sulfur 0.7 Sodium 0.7 Potassium 0.5 Calcium 0.7 Magnesium 0.5 Iron 0.1 Wei ht .W i ht % By-products (gases,J H20, volat1le ac1ds Wfp Undecomposed organic Microbial W I matter Wf cells fc ° N . Undecomposed __ organic wfi * matter 1 Minerals J41“ Minerals 1% Initial condition Partial decomposition Figure 3.6 Schematic diagram showing sludge solids, before and after partial decomposition (after Al-Khafaji, 1979). 50 the prepared sample was placed in a refrigerator so as to inhibit de- composition. Three (CTU) triaxial tests were then performed on this material and the results compared to those of the fresh material in order to isolate possible effects of the nutrients and seeding material on the undrained shear strength from the effects of decomposition. Due to the expected decrease in sample permeability with decomposition (Figure 2.11) a deformation rate of 1.4x10"3 in/min was used for (CIU) tests on partially decomposed samples. CHAPTER IV EXPERIMENTAL RESULTS The experimental results presented in this section provide informa- tion regarding the physical properties and the stress deformation be- havior of the papermill sludge. A. Physical Properties of the Papermill Sludge Table 4.1 sumarizes the physical properties of the primary and combined papermill sludge samples. Information on the water content, solids content, organic fraction, unit weight, specific gravity, and pH is provided. The average water content for the two sludge types are converted to solids contents through use of equation 2.1. Based on mea- sured values of organic fraction and solids content, the combined sludge sample appears representative of the sludge generated during 1979 (Table 4.1). The pH of both sludges was measured to be 11.9 at the time of sample procurement. Subsequent measurements showed a gradual decrease in the pH with time. The observed decrease was more pronounced for the combined sludge than for the primary sludge. 8. Stress Deformation Behavior of the Sludge Stress deformation characteristics of the two sludge materials were evaluated in laboratory consolidation tests and triaxial shear tests. Duplicate consolidation tests provided comparative information on the compressibility of the two sludge materials. The shear strength was evaluated for fresh samples of primary and combined sludge and partially decomposed samples of the combined sludge. 51 52 1. Compressibility The consolidation test results are summarized in Table 4.2. The results of three consolidation tests for primary sludge samples on a strain versus logarithm of effective pressure plot are shown in Figure 4.1. Curves Q-P1 and Q-P2 represent rapid load increment (quick) tests in which the effects of secondary compression are minimized. Curve C-Pl represents conventional consolidation test (Bowles, 1978) results uti- lizing 24 hour load increments. This test method includes varying amounts of secondary compression during each load increment which may account for the higher Cc value. Figure 4.2 summarizes the consolidation test results for the combined sludge samples. Curves QACI and Q-C2 represent quick tests, while curve C-Cl is for a conventional test on the combined sludge. Here the value of Cc for the conventional test is between the quick test values. It is seen that the combined sludge is more compres- sible than the primary sludge based on values of Cc‘ Single load in- crement tests (MacFarlane, 1969) using anticipated field loads were per- formed to better simulate possible field conditions and to distinguish between primary and secondary compression more clearly. Figure 4.3 compares typical settlement versus logarithm of time data for primary and combined sludge samples under a load increment of 0.1 to 0.8 kg/cmz. The higher compressibility of the combined sludge shown in Figure 4.3 was typical of all single load increment test results. The coefficient of secondary compression, CCK, shown in Figure 4.4a increased over the range of consolidation pressures from 0.2 to 6.4 kg/cm2 with the com- bined sludge exhibiting higher Ca(values. Values of the coefficient of consolidation shown in Figure 4.4b were determined by the square root of time fitting method. The effects of secondary compression in conventional 53 test made use of the logarithm of time method for determining cv dif- ficult. Data for cv obtained from logarithm of time curves for single load increment and 24 hour load increment tests are listed in Table 4.2 for comparison. The coefficient of permeability, k, was also determined indirectly from consolidation test results. Average values of k for a range of consolidation pressures for the primary and combined sludge are shown in Figure 4.5. Previous research has found the permeability of partially decomposed sludge to decrease with increasing decomposition (Al-Khafaji, 1979). Figure 4.6 summarizes the results of tests on model sludges and the com- bined sludge used for this study. The values of cv for fresh samples of combined sludge were found to decrease nearly 80 percent as a result of 26.6 percent decomposition. Isotropic consolidation of triaxial test specimens provided the data for the papermill sludge. More complete test data is given in Appendix D. 2. Shear Strength of Fresh Sludge The results of triaxial tests on fresh samples of primary and com- bined sludge are summarized in Table 4.3. Data from consolidated—un- drained (CTU) and consolidated-drained (CID) triaxial tests are provi- ded. Typical stress-strain curves for CIU tests on combined sludge, given in Figure 4.7, show increasing stress at strains over 20 percent. This behavior was observed for all tests on fresh sludge samples; thus failure was taken at 20 percent axial strain. Typical results of a CIU test on primary sludge are presented in Figure 4.8. The obliquity ratio 51/73, deviator stress (0‘1- c'7T-3), pore pressure change Au, and pore pressure parameter A are all plotted against axial strain. The obliquity ratio becomes very large at higher axial strains due to the 54 small effective minor principal stress (7‘3. A gradual increase in the deviator stress with increasing strain is observed and A approaches a constant value of approximately 0.6. Results of four CIU tests on the primary sludge are summarized in Figure 4.9. The if - 9} plot shown in Figure 4.9a yields values of 3'= 63.4 degrees and E'= 0 through use of the transformations shown in Figure 2.7. Figure 4.9b shows the change in final water content with consolidation pressure, and Figure 4.9c compares the undrained strength with consolidation pressure. Figure 4.10 shows typical results of a CIU test for the combined sludge. The effective angle of internal friction 5, final water content, and un- drained shear strength (cu) are summarized in Figure 4.11. A friction angle of U'= 49 degrees and cohesion intercept of E'= 0.21 kg/cm2 give the combined sludge a lower shear strength than the primary sludge at pressures greater than 0.25 kg/cmz. Figure 4.11b shows the final water content versus effective consolidation pressure for the combined sludge. Figure 4.11c gives the undrained shear strength of the combined sludge for various consolidation pressures. Typical results of C10 triaxial tests on primary sludge are shown in Figure 4.12. Results of two of these tests, shown in Figure 4.13 on a'pf -'a; plot, give 3'= 33.2 degrees and E = 0.116 kg/cmz. Typical stress-strain and volume change data for a combined sludge sample in the C10 test are given in Figure 4.14. The results of three of these tests are summarized in the if -'qf plot shown in Figure 4.15. A'E = 0.113 kg/cm2 and $’= 23.0 degrees for the combined sludge give it a lower shear strength than the primary sludge. 3. Decomposition Effects on Shear Strength To evaluate the effect on shear strength of nutrients and seeding 55 material added to aid decomposition, a series of three CIU tests were run on the freshly mixed material prior to decomposition. Typical re- sults of one of these tests are shown in Figure 4.16. Note the addi- tion of nutrients to the combined sludge causes the obliquity ratio to be smaller and the pore pressure parameter (A) to be larger than values observed for the fresh combined sludge. A summary of the results of three CIU tests on the combined sludge with nutrients and seeding mater- ial added is given in Figure 4.17. Comparison of Figures 4.17 and 4.11 show the addition of nutrients to have decreased 3 from 49 degrees to 39.6 degrees. No measurable change in E'or the final water content were observed, but the undrained strength cu decreased with addition of nutrients and the seeding material. The effect of decomposition of the organic fraction on the shear strength of the combined papermill sludge was measured in a series of five CIU triaxial tests with pore pressure measurements. Changes in the organic fraction during 25 days of decomposition were measured by ignition of small samples at various stages of decom- position. Partially decomposed samples were partially air dried and stored at 4°C until testing. Storage at this low temperature slowed decomposition to a level which allowed a series of five CIU triaxial tests to be performed at the same level of decomposition. At the time of testing, the average degree of decomposition using equation 3.2 was 26.6 percent. Typical results of one of these triaxial tests are shown in Figure 4.18. Due to a decrease in the influence of fibers on the material shear strength, a peak value on the deviator stress versus strain plot is observed at about 16.6 percent strain. This peak deviator stress was observed in 4 of the 5 CIU triaxial tests performed on the decomposed 56 sludge. Results of the 5 tests performed on partially decomposed sludge are summarized in Figure 4.19. The 6} -'5f plot in Figure 4.19a gives '3 = 28.7 degrees and E'= 0.11 kg/cmz. Figure 4.19b shows the final water content versus consolidation pressure and Figure 4.19c compares the undrained strength (cu) with consolidation pressure. The scatter of data results from inconsistencies in the degree of consolidation due to decomposition and the associated gas generation which occurred during the CIU test. Further effects of decomposition are discussed in the next chapter. 57 TABLE 4.1 PHYSICAL PROPERTIES OF THE PAPERMILL SLUDGE Property, Combined Sludge Primary Sludge water content (% of dry weight) 318 270 solids content (1) (% of total weight) 23.9 (24.6)* 27.0 organic fraction (2) 0.58 (0.54)* 0.49 unit weight (lb/ft3) 69.2 70.9 specific gravity (3) 1.89 1.91 pH (4) (range of values) 8.3-7.6 10.3-8.6 (1) Solids content of fresh sludge. Related to water content by the equation: w% = 100( 100 ___ [% solids by wt.-1 (2) Organic fraction. X = 1 - 1.02(W2/W ) where W = oven dry sample weight prior to ignition and W2 = weight of asA after ignition at 400 C. (3) ASTM 0854-72 test method. (4) Measured values at treatment plant were 11.9 for both sludge types. * Average of values collected daily by Nekoosa Papers, Inc. for 1979. 58 NN.Nm 1- e.o - N.m mm.oe - N." - o.oH NN.NS Noo.o o.oN- ¢.e oN.Nm mflo.o e.» 1 N.m mm.om NNo.o N.N 1 m.“ Ho.me eNo.o a.” 1 m.o NN.N¢ - N.o - a.” oe.m¢ 11 a.“ 1 N.m mo.ae mmo.o N.N - e.N 64.He eeo.o e.H 1 m.o NN.NN Nmo.o N.o - ¢.o mN.mN mNN.o 4.0 - N.o embaaeou 4N.NH eduaasou NNN.o N.o 1 H.o Soc mem.e mo.N m¢.NN be: NNH.o H.o 1 o.o Na - o me.Nm 11 ¢.o 1 N.N No.Nm -1 N.m 1 o.oH NN.Nm efio.o o.oN1 ¢.e HH.Nm mNo.o e.e 1 N.m mm.me Nmo.o N.m - e.N e¢.me NNo.o Q.H - m.o Ne.N¢ .- m.o 1 e.N em.me .- a.“ 1 N.N mm.ee meo.o N.N - e.H mm.mm eNH.o e.H - N.o mm.eN 46H.o N.o - ¢.o 4N.NH mmN.o e.o 1 N.o edbsdsou Nm.- eduadsou mHN.o N.o - N.o be: mNe.m 4N.N NN.N be: eeN.o N.o 1 o.o Ha 1 a dd 6 Aug, aces\Nsdv Amadxmxv you 3.3.. 32, u 523 we: mop 25w) a mew-55 39:3 .53 .a_»_=, >6 vac, duezpm 3.1531 hmwh zopgsomzou 1.5 £3223 «é m._m<._. 59 Hm.Hm noo.o N.m 1 m.~ Hm.~e mmm.o m.~ 1 m.o mm.ue 11 m.o 1 o.H fim.w¢ 11 o.~ 1 ~.m m~.m¢ mmo.o m.o 1 m.~ mo.oe mmo.o m.H 1 w.o mm.om mmo.o m.o 1 «.0 mm.~N owo.o e.o 1 «.0 vouzaeou Hm.~ nop=QEou oH¢.o ~.o 1 H.o uoc omm.n mm.w Ho.o uo: moH.H H.o 1 o.o Ho 0 mwmo.o mmo.m 11 mm.me mmo.o mmno.o ~.m 1 H.o ea Hm emmo.o owe.“ 11 mm.ee m¢o.o mmH.o o.H 1 H.o ma Hm ommo.o mo~.m 11 oe.mm Nmo.o omH.o w.o 1 ~.o mm Hm mwfio.o Hmm.m 11 n¢.e~ moo.o mm~.o «.0 1 H.o Hg Hm 11 11 11 11 e.o 1 ~.m 11 m~.mm 11 11 ~.m 1 o.o NNo.o um.nm Hfio.o «No.o o.oH1 ¢.o «Ho.o mH.mm Neo.o eeo.o ¢.m 1 N.m 11 om.me 11 11 N.m 1 o.H 11 m~.He 11 11 m.H 1 m.o 11 m~.o¢ 11 11 m.o 1 o.H 11 um.~e 11 11 o.H 1 ~.m oumo.o mw.me moo.o Hmo.o ~.m 1 o.” 11 Hm.cm mH~.o Nofi.o m.H 1 w.o 11 om.m~ 11 cmm.o m.o 1 ¢.o mHHo.o m~.- oom.o mmm.o e.o 1 ~.o 11 ¢H.m 11 mHm.c ~.o 1 H.o 11 com.“ mc.m m~.m 11 omm.o H.o 1 o.o Ha oo o Amy acmE\~Eov NNEU\mxv Sou ovum; uwo> o =1m1pm we?» mop > mENW> ucmsmeucF mPnEmm one» Fawpwcr o emop mauspm .ucou ~1e m4m 0 000000 0500 000 > 0500) 0 0500000 000500 0000 0000000 0 0000 000000 .0000 ~.0 mgm<~ 61 at? 1 £20 1 520... 1- 1 x0000 00000000500 11 00 00000000500 000000000 00 00000000000 11.80 0000000000000 00 00000000000 11 >0 000000 00000500 .00000 000500000 0000 000000 11 0 0:0.0.~.00100 000000 0005000 .00000 000200000 0000 000000 11 0 0:0.0.~.00100 000000 00:00:60 .0000 0000000023011 0010 000000 00000500 .00000 0000011 m 000 0010 000000 0002000 .0000 00000000>00011 0010 000000 0002000 .00000 0000011 0 000 0010 11 00.00 11 11 0.0 1 0.0 11 00.00 11 11 0.0 1 0.00 11 00.00 5000.0 000.0 0.001 0.0 0000.0 00.00 0000.0 000.0 0.0 1 0.0 11 00.00 11 000.0 0.0 1 0.0 11 00.00 11 000.0 0.0 1 0.0 11 00.00 11 11 0.0 1 0.0 .0000 11 00.00 11 11 0.0 1 0.0 00 1 0 00 0 000 000550200 0 505000 010 00000 000> 0 000000 0200 000 > 050w) 0m0E0euc0 000200 0000 0000000 0 0000 000000 .0000 «.0 ugma<2200 0.0 m00<0 m.NH mH.o -u .. ~.wm mHH.o cpmcmLum xmma mmuaFm ammoasoumu N.mH wH.o .. .. m.o¢ oo~.o cwmgum Now mmwuwwgwmmwmwww w.m~ m~.o o.m~ omH.o o.me mHN.o :mmgum Rom mmuapm umcwasou oJNN oo.o ~.mm mHH.o ¢.mo ooo.o :mmgpm Now wmvapm xgmsvga awsfiANfiMwK. 32% $835 w 5% $535 w mgmqumgmq gumcmgpm mmmgpm page» pmwp oHu mgmumsmgma sumcwgpm pmmu :Hu mwgwuwg mmmgpm m>wpuuHHw mgapwmm nwszmm u cmswumam m ummu 63 mmmhuzmc-c1 cC = 0.302(1 + e0) A 20 r 0’ E? ,E 40 . 2 4.: (f) 60 " . 3\ 80 1 lglnnjal 1 l AllalLJ 0.1 1.0 10.0 Effective consoidation pressure (Te (kg/cmz) Figure 4.2 Strain-effective stress reiationships, combined siudge mmmuz—m cmcwneou ucm acmemga go; we?“ mo p p Egpwcmmog mamgm> mcwunmc mev commmmcasou m.¢ mgamwm J D b D A 0 o > O O /> / o o bflllu 825 u 8: 1 O D o .11: o All 83.0 n 8; . 11/ my D O/ m 1 . 3 / m. n w . p m“ 6 J 4 6 m n m U. A 5 figs "3 89° "3 w 4 SEN5 :85 u >0 5.: .8 N85 u 3 n m. Eu mmu.o n m>m= s ¢~N.o " m>mx ,\ NEU\mx m.o-~.o acmEmLucw two; NEo\mx m.o-H.o “cosmgucm coo; . ANU-HmV mauspm uwcwnsoo Ama-Hmv mmuapm semewca o w NV nu . 3 b/, Ammuacwev mewh ,/Ia P - n P L — n L n b p L p P b P L o.ooc~ o.ooc~. o.oom o.ooH o.o~ o.om o.o~ o.oH o.~ o.m o.~ o.H ~.o m.o ~.o H.o om.o NH.o «H.o HH.o wo.o mo.o No.0 67 a L) g 0.045 _ .3 <7 8 $- Q- h E O U >‘0. E 035 l- 'U C O U 3 r- “5 .p 0.025 _, C) Primary sludge 5 single increment tests 6 i: _ V7 Combined sludge ‘3 single increment tests 8 & conventional tests 0.015 A J 1 I 1 I 1 ’J 0.1 0.2 0.5 0.7 1.0 2.0 5.0 7.0 10.0 Consolidation pressure 07¢ (kg/cmz) 0.3 _ (b) 9 O H Coefficient of consolidation cv (cmZ/min) 0 Primary sludge Q-Pl V Combined sludge Q-C2 0.1 Figure 4.4 J J a l 1 Q 0.2 0.5 0.7 1.0 2.0 5.0 ;.0 $0.0 Consolidation pressure 62 (kg/cmz) Consolidation characteristics of primary and combined sludges (a) coefficient of secondary compression, Cat (b) coefficient of consolidation, Cv‘ "LO .mmmuzpm nmcmaeou vcm xcmewga Low mczmmwca cowumuwpomcou m>wuomwmm mamcm> .x .xpWFwnmmsemq we pcmwumwwmou m.¢ mesmwd 33.23 J. 3:28:23 mo “53.538 o-o~x n-o~x m-on m-on ofluofix m H m N u u dill . m .m m m m m m m H / _H ~.o 8-0 9 L o; 3-0 0 O /D //o .2. // O /D g 68 o.oH aJnssaJd uog1epglosuoo angqoa;;3 ‘ 2.2 ZuJD/bx 69 .mmmcaHm HHHELmama nmcwneou can HmNmH .Hnmmmcxup< Lmuwmv mmHQsmm mmusHm Hmuoe Low :oHumuHHomcou mo acmwummemou ecu co mpummwm cowummoqsoumo m.¢ mesde Hwy :oHuHmanoUmo om mm om me ow mm om mm om mH 0H m o ’ q d A.\ d 1 u + d a u + O 40 N o' L Q. Q 0’ EU\u . .. o :2: .26.. 3:3 No a v. mwu we a o $353 33 Hmwxmtu “Ho NE \ v. mu H u .b D xmm n mx mag? O . 5331028 3333., N539. o.H u Nb 0 Stigma 8:258 msuEm mém u mb D wow u 8x 4 m o HmNmH .mewmgqu< Lmummv NEU\Em m.mm u Wm AV mmHgEmm Prom mama ummu compmuHHomcou NEU\sm m.HH u ww nu uwcmmgo Hmvoz . o.H 0Ao/Mo ‘uo;1ep;losuoo go 1u3;3;;;303 Deviator stress, 5;— i=3 , (kg/cmz) 70 3.0 , ,000’0'0 : 0-0/00'0"? 0’0’ cu-c3 /o/ EE= 2.5 (kg/cmz) O/O / 2 0 i- .. ,0 , '0’0’0 /0/0 0 00-02 ,0/0/ §= 1 75 (kg/cmz) 0/0 010 VHV’V’V’V’V N'V/V’V’v’v’v’ 1 0 _ WV CU-Cl fl’v’v (_l‘c= 0.92 (kg/cmz) l 0 l I l l l J l I l l J 0 2 4 6 8 10 12 14 16 18 20 22 Axial strain (%) Figure 4.7 Deviator stress versus Axial strain for combined sludge samples at various consolidation pressures 71 25 , ‘// consolidation pressure = 1.0 kg/cm2 ///)D 20 P back pressure = 2.5 kg/cm2 - b0”) \v—i 1'5 n b i? 10 . 'S if '3 5 . O 0 n l L l L l A l n J O 2 4 6 8 10 12 14 16 18 20 Axial strain (%) Figure 4.8 Axial strain versus Obliquity ratio, Effective deviator stress, Pore pressure, and Pore pressure coefficient, A, curves for primary sludge sample CU-Pl. , kg/cm2 ands Final water content % dry weight gth Undrained stren cu, kg/cm2 72 {Eu 41.80 2 . sin 3 = tanR o 1' = 63.40 c = 0.0 1 . (a) 0 - - a 0 1_ _ _2 3 Pf = (away/2. kg/cmz 150 [ \OCU-PZ CU-Pl 140 . 130 . 120 _ c - 4 CU-P3 U P 110 n l ‘ 0 1 2 3 Consolidation pressure, 65 2 ‘F (kg/cm ) 0 1' 2 3 2 Consolidation pressure, fig (kg/cm ) Figure 4.9 Consolidated-undrained triaxial test results for primary sludge samples. (a) kf failure line (b) final water content (c) undrained strength. 73 consolidation pressure = 0.92 kg/cm2 back pressure = 3.58 kg/cm2 Obliquity, (Ta/673 _. 2 (a1 " 0.3) kg/Cm N E U \ U5 x 5' ‘4 1.0 p 0 O c: 0.5 , o 9 ‘9 ° 0 A l L i I A l A A _A 0 2 4 6 8 10 12 14 16 18 20 Axial strain (%) Figure 4.10 Axial strain versus Obliquity ratio, Effective deviator stress, Pore pressure and Pore pressure coefficient, A, curves for combined primary and secondary sludge sample CU-Cl. Final water content % dry weight Undrainedzstrength cu, kg/cm 74 /=370 sin 5 /////£) 2' 1 c Cf//// (a) o/ . . , 3 ta r13? 49° 0.21 kg/cmz 165' CU-Cl 155' 145 . 135 _ 125 g, . . cg:;3 0 1 2 3 Consolidation pressure 6; , kg/cm2 2 . C (y" u ——-= 0.4 p 8 1.. C) ////’////’ (C) 0 . . ._J 0 1 2 3 Consolidation pressure 0; , kg/cmz Figure 4.11 Consolidated-undrained triaxial test results for combined primary and secondary sludge samples (a) kf failure line (b) final water content (c) un- drained strength. 75 3.0 2 consolidation pressure = 1.0 kg/cm2 kg/cm _<§3, N c: H O Deviator stress 6? j I l l J l l l L A 0 2 4 6 8 10 12 14 16 18 20 Axial strain (%) 16 Volume change AV/Vc (%) 20 b Figure 4.12 Typical results from a consolidated drained triaxial test on primary sludge sample CD-Pl (a) deviator stress (b) volume change. 76 .mquEmm mmqum xgmswca Low mqummL pmwu Hmwxmwcp cmcwmguaumumuHH0mcou mH.¢ mczmwd NEo\mx .N\Hmmm + Hmwv u a o.w oK ed o.m oé o.m o.~ o.H o L: W q q 1 u d 1 n O .H. .m 10H .0 O : Tm“ AooN . a. CC nu NEE 8:5 u w .2 30.0 n m m 9N2 u w .o m m 2 058 u m. Aoé o.m 77 2.0" consolidation pressure = 1.0 kg/cm2 N515, / \ 3’ 2” “:5 I k;, 1.0 _ U) m (D S. 4..) m g 0.5 P F3 g (l) C) l l l l I 4 6 8 10 12 14 16 18 20 Axial strain (%) CD 12 16 20 - Volume change,AV/Vc (%) 24 b Figure 4.14 Typical results from a consolidated-drained triaxial test on combined sludge sample CD-Cl (a) deviator stress (b) volume change. 7i = (cit—5'3 )l2. kglcm2 78 161: 21.30 0 3: 23° 2 L E = 0.104 kg/cm "c" = E/cost = 0.113 kg/cm2 1 2 3 4 5 5 = ( 57-1-53 )/2. kg/cm2 Figure 4.15 Consolidated-drained triaxial test results for combined sludge samples. 753 Obliquity, 0? ), kg/cm2 “1' "'3 ( Au, kg/cm 79 20 - consolidation pressure = 1.0 kg/cm2 /////;D 15 , back pressure = 3.5 kg/cm2 10 - (D / 5 P 0/0 ”OJ/0’ (a) o>° ‘D 0 L A A A A A A A A A J 0 2 4 6 8 10 12 14 16 18 20 0/0 (3"" (3“" 1.0 - 0"" ”/0 0. (b) 8 10 12 14 16 18 20 1.0 r O O____o_——O ’0 0.5 . 00’0‘ : (c) 0 f- A A A A A j A 4 0 2 4 6 8 10 12 14 16 18 20 1.0 - W%'“0’O_O_H‘“O 0.5 709’ ' (d) 0 A A A A A L A I A A _- 0 2 6 8 10 12 14 16 18 20 Axial strain (%) Figure 4.16 Axial strain versus Obliquity ratio, Effective deviator stress, Pore pressure and Pore pressure coefficient, A, for combined sludge with nutrients added, sample CU-CNl. N E e 2 03 at NO 2: (0 lb) 1 I lb- II g. It? 0 165 .p c .3 c 155 O U 226‘ mm 145 +3.!- ‘50) 33 23?: 135 EU Kiss 125 2 .c 4.) 0'1 c O) .3 mm 1 ‘05 030 C\ CPU} «5.2 L 'U 0 C 3 DU 0 80 ‘ a: 32.50 (a) j = 39.60 2 b [/13 c = 0.208 kg/cm 1 2 3 ‘6, = (51+ (1'3 )/2, kg/cm2 Consolidation pressure 01;, kg/cm2 (C) L A _A 1 2 3 Consolidation pressure 6;, kg/cm Figure 4.17 Consolidated-undrained triaxial test results for combined sludge samples with nutrients (a) k failure line (b) final water content (c) undrained strength. Obliquity, 07/63 (67—63). kg/cm2 Au, kg/cm2 81 H—o o/O/O/O 4 .. 0’0/ 0 O/ 3 . 2 . consolidation pressure = 1.0 kg/cm2 back pressure = 3.5 kg/cm2 1 0 '1 : .O___o_—o—o—o—o—-0% 69-0 0’0/0 05. 0 A A A A A A A A L A 0 2 4 6 8 10 12 14 16 18 20 Axial strain (%) Figure 4.18 Axial strain versus Obliquity ratio, Effective deviator stress, Pore pressure and Pore pressure coefficient, A, for partially decomposed combined sludge sample CU-CDl. qf = (Eu-5‘3 )/2, kQ/Cm Final water content % dry weight Undrainedzstrength 82 1.0 - = 25.650 28.70 0.11 kg/cm2 0.5 r 0.0 ‘ ‘ J 0.0 ._ 0.5 __ 1.0 2 1.5 Pf = (6+ 6'3 )/2, kg/cm 115 P OCU-CDl 110 * 000-004 105 p U-CD? 100 ! CCU-002 CU-CDS 95 A A J‘ 0.0 1.0 2.0 3.0 Consolidation pressure 65 , kg/cm 1.0 r 0.0 - ‘ i: 0.0 1.0 2.0 __ 3.0 Consolidation pressure at , kg/cm 2 Figure 4.19 Consolidated-undrained triaxial test results for partially decomposed combined sludge samples (a) k failure line (b) final water content (c) undrained strength. CHAPTER V ANALYSIS AND DISCUSSION OF RESULTS In addition to providing information necessary for a qualitative assessment of the engineering behavior of a papermill sludge, the physical properties, including water content, unit weight, specific gravity and organic fraction are useful in evaluating the compressibil- ity and strength of a sludge landfill deposit. A. Physical Properties From data gathered daily at the mill during 1979, the observed sol- ids content (dry weight basis) of the freshly dewatered sludge ranged from 18 to 43 percent (Appendix A). Equivalent water contents on a dry solids basis ranged from 456 to 133 percent,respectively. Variation of the organic fraction appears to be responsible for much of this varia- tion. Measured ash contents varied from 28 to 81 percent giving an organic content between 72 and 19 percent (Appendix A). The higher organic fractions generally lead to higher water retention in the sludge. During dewatering operations the rate of application of the secondary sludge varied depending on solids capture efficiencies and visual appear- ance of the dewatered sludge cake. This factor accounts, in part, for the daily variation in the organic fraction of the dewatered sludge. Pulp fiber is probably the main source of the 49 percent organic content measured for the primary sludge. Addition of secondary sludge increased the organic content to 58 percent and the average water content from 270 to 318 percent. The increase in organic content, from addition of 83 84 biological solids (secondary sludge) represents little increase in the amount of pulp fiber. Implications of the higher water content are considered later. Specific gravities of the two sludge types given in Table 4.1 are similar, with the lower value for the combined sludge resulting from the lower specific gravity of the biological solids. The average measured specific gravity for the primary sludge, equal to 1.91, was slightly higher than the value for the combined sludge, equal to 1.89. This small difference, together with the difference in water contents indi- cates that the total unit weight of the primary sludge should be higher than the combined sludge. The unit weight values measured by packing the sludge into 1/10 cubic foot buckets, listed in Table 4.1, were 69.2 lb/cu.ft. and 70.9 lb/cu.ft. for the combined and primary sludge, respec- tively. Incorporating the average water contents yields dry densities of 16.6 lb/cu.ft. and 19.2 lb/cu.ft. for the combined and primary sludges, respectively. The hydrogen ion concentration (pH) is a measure of the acidity or alkalinity of sludge. Perhaps the most significant factor regarding the pH is its' change with time. Anaerobic decomposition, when carried to its full extent, produces synthesized cellular material, the meta- bolic waste products methane and carbon dioxide, and a residue of non- degradable material. Anaerobic conversion of organic materials to me- thane can be separated into three steps: 1) Hydrolysis, in which large complex organic molecules are enzymatically broken down into smaller molecules capable of being transported into the cell; 2) Acid fermenta- tion, which is the intracellular conversion of smaller molecules into a variety of organic materials of which the most important are short 85 chain volatile acids; and 3) Methane production, or the conversion of short and long chain organic acids to methane. The acid fermentation phase involves the production of volatile acids which will lower the pH. If unchecked the pH may be depressed below 6.0, a range which is toxic to methane producing bacteria. During sample procurement, the sludge pH was measured at 11.9 by personnel of Nekoosa Papers. This value was said to be typical. Subsequent measurement showed a decrease in pH for both sludges. Figure 5.1 shows the pH of the combined sludge to have decreased more than the primary sludge. This pH change occurred while the samples were stored at 4°C in sealed containers. The pH of the com- bined sludge decreased from a value near 12, where few micro-organisms can exist, to a value of about 8 which is favorable to most micro- organisms. Although no measurable change in the organic fraction was observed during this time, various odors were produced and both sludges became blacker in color. The foul odors and color change occurred sooner and became more distinct in the combined sludge samples. Based on these observations it would appear that both sludge samples were slowly enter- ing the initial stages of decomposition. B. Decomposition Observations Accompanying the decomposition process was a decrease in the sludge organic content as measured by equation 2.3. Use of the initial organic fraction (xfo) and the organic fraction after partial decomposition (xfi) in equation 3.2 permitted evaluation of the degree of decomposition. A pulp fiber with no decomposition is shown, magnified 1600 times, in Figure 5.2a. The 10 micron scale bar shows the fiber to be approxi- mately 44 microns in diameter with holes having dimensions ranging up to 8 microns. After 25 days the average degree of decomposition, based on pH 86 12 11 /— primary sludge 9 P 8 , ‘;r”“’combined sludge 7 A A A L 0 50 100 150 200 Time, days Figure 5.1 pH versus Time of sample storage at 4°C in sealed containers 87 the ignition test, was 26.6 percent. Figure 5.2b shows a fiber at this stage of decomposition and indicates a general breakdown of the fiber's structural integrity. Another fiber shown in Figure 5.3a, under higher magnification, shows rod shaped bacteria on the fiber surface. At 20,000 magnification, these individual bacteria, slightly longer than 1 micron, appear as in Figure 5.3b. Periodic observation of the sludge mass as it decomposed revealed an apparent increase in sludge volume in each of the sample containers. Upon stirring, large amounts of gas bubbles were released and the sludge volume decreased. Gas production rates of 14.5 percent per volume of sludge per day have been observed for decomposing sludge samples with a carbon to nitrogen ratio of 36:1 (Alexander, et al., 1978). Due to the lower permeability of the partially decomposed sludge, gas migration may be very slow, effectively trapping gases produced by decomposition. This trapped gas may significantly alter the stability of a landfill deposit due to a decrease in effective stresses in the sludge mass. C. Consolidation Characteristics The highly compressible nature of papermill sludge is due mainly to the organic material it contains. Pulp fibers have a high water holding capacity which gives the sludge a high water content and void ratio in comparison with inorganic soils. These factors result in large changes in sludge volume due to applied stress. Figure 5.4 compares typical results of consolidation tests on the primary and combined sludges. Based on the compression index (Cc) the combined sludge appears to be more compressible than the primary sludge. This would be expected from the higher water contents and higher initial void ratios observed for the combined sludge. Example settlement '5 _u . . llh Figure 5.2 (a) 1600 magnification of a single fresh pulp fiber (b) 2000 magnification of a single pulp fiber after about 27 percent decomposition. IIZEIII 80 Figure 5.3 (a) 5400 magnification of decomposing pulp fiber with bacterial cells (b) 20,000 magnification of bacterial cells attacking pulp fiber. 90 0 () Q-Pl CC = 0.289(1+e0) 0 V Q-CZ Cc = 0.305(1+e0) V 20 - 9 V 0 V o 40 - o——______;___ ““ 9 g? V V‘ V 2, C}~_““‘-—————____ V o E ~0— g 60'— V7—————__________ Q7. ' 4.) _F-i U) V 80)- 100 A A . l . A A _J 0.1 1.0 10.0 Effective consolidation pressure 53c , kg/cmz Figure 5.4 Comparison of strain-effective stress relationships for primary and combined sludge. 91 calculations for fresh primary and combined sludge are shown in Figure 5.5a and 5.5b, respectively. These figures show primary settlement estimates based on no initial or residual pore pressures using equation 2.5. Settlement estimates are for a 40 foot thick sludge layer subjected to a 440 psf surcharge. This pressure was estimated to be representative of a cross section consisting of a 1 foot sand drainage layer, a 2 foot layer of compacted clay covered by 1 foot of vegetated topsoil. The example calculations give primary settlement estimates of 22 and 24 inches for primary and combined sludge, respectively. Also shown in Figure 5.5 are primary settlement estimates based on equation 2.6. Re- sulting primary settlement estimates of 7.1 and 13.1 inches were calcu- lated for primary and combined sludge, respectively. These estimates are much less than predicted from equation 2.5. Secondary compression estimates using equation 2.7 are also included. These estimates are based on a 10 year period where secondary compression theoretically begins after primary compression is complete. Secondary compression estimates of 2.4 and 1.5 inches were calculated for the primary and combined sludge, respectively. A major reason for the higher secondary compression of the primary sludge is the longer time period over which secondary compression occurs in the primary sludge. Figure 5.5 shows estimates for the time required to complete primary compression for the two sludge types. It is seen that the time required for completion of primary compression of the primary sludge (3.3 years) is about half that required for the combined sludge (6.5 years) due to the lower permeability of the combined sludge. Figure 5.5 also shows estimates of the volume of leachate expelled from a 1 foot square column of sludge 40 feet thick. These calculations show that one acre of primary sludge, 40 feet thick, will release 92 .mmuaHm umcwnsou Hay wmuapm xsmEHLa Hay em>ou Hue?» we acmEmumHa o» man mHHa ammv poem cc m :H vmumHa wavaHm com mcoHuuHcmgg pcmEmHuumm m.m mgamwd Hay waive? ¢.N u mM\oH moHH--omevHH.o n au\p mop zxu u m: mtua\Ham omMINmm menu» oH cw acmempuumm Agmucoumm N»C\muemm.H.u HcHNH\ueHV=HNN :onmqusou Homemgq :HE\ :Hmm.o >6 cszHou Nam H muqueou op mgmmaTm.m u N-\mmeVHHu u NNNVG:QF u an conmmemsou Acmemgq :onmmmmEou asuEHLn go» mswh mchsu uwmau—ms oumgunmd :wwmm.o o o mucus? H.N u HmeHH.o-HHmH.oV x Hpe\=H~Hvucoe u Hxnw x H :\c I u eras o .IIIIIIII: m>m 8: 855 NN u I w u 8 mm" m o ? b\.v m3. uu n w i am; oeem mmmmmepm pcmstuamm HumEHga mcHugum * umn ooom $23 .. o mm.H~ n~.~ \ wmvaHm gamma 1 oH mm.m \ R~.m - i ON nH.¢ mum mm..x Rm.m\. .2266 :3: I\ 1 on &~.m\\\. op mau mmmgum go>ou www.mfl PMC—L. “_Un— OHH u ..I%- l Dc 8.. o: H. L om 93 aeum\_mm mmI.HmI N»I\mpcm HIHNH\80HI=H¢N csapou um H m commmmLQEoo Homemcn;mcwczu vmmmmng mpmzummg mqucH m.H mww , OHIOHAIN-OI¢VHHC.O £32: I .6 u mI mmIUIH H.mH u HINIH.o-wHN.ov HSI\=2Nvaeo¢ u FIda PoI\.SI u mgmmxToH :H ucmEmepmm Hgmccoomm 9 WE. .b\u.bmoH uu "\w u mcmmgpm xa.¢l1 wH.N\ N¢.N\ Im.~\ Nm.m\. xm.¢ . \\ RN 0 Op m meWW\\. xx.¢H .umzcmucou m.m mesmwd HIV commmmgasoo agmswga mum—aeou op mgmma m.mH u :22 =_mmoo.o N \OOIVHHV u an mgsuuo :oHuHmoQEoumu No.mm 4H >8 :HE\ cw Ho.o commmwgaeou Acmemga a NH \OIIVAHV u NHN\ IIH u p mHmHano op memo» m.o u ucmEmHuumm agmswgq Low mew» cw emn.o m :AV O .855 E u Im>mw m 8 wIm." m acmEmHapmm Humswga ma comm -mammmcpm mm; ommm + J 0 mm a m Amman c H 1.oH mun mm 0 b 11om gm>ou Hmcwm 1 ac mmmmmcum Lm>ou om Hmcmw a nun. ll 1 cc um; o¢¢ > L om 94 approximately 597,350 gallons of leachate, compared to 651,658 gallons for the combined sludge. These calculations used the previously des- cribed primary settlement estimates for the respective sludges. Figure 5.5b shows an additional calculation for the time required to complete primary compression assuming 26.6 percent decomposition in the sludge. The decrease in the coefficient of consolidation (cv) would theoretically increase the time required for primary settlement to 19.5 years. This slow drainage has implications relative to landfill sta- bility which will be discussed in a following section. Figure 5.6a and 5.6b present similar calculations for a configur- ation of 10 foot thick sludge layers separated by sand drainage layers. The settlements given in this example are for a 10 foot thick sludge layer and should therefore be compared to Figure 5.5 with that fact in mind. In addition to changes in settlement magnitudes are the decreases in time required to complete primary compression. The sand drainage layers separating 10 foot thick sludge layers will decrease the time required for primary compression by greater than a factor of 10. Secondary compression estimates in this example are based on 1 years time. In the example in Figure 5.6 primary settlements from equation 2.5 and 2.6 compare reasonably well. It should be noted that these settle- ments and the resulting leachate volumes are less than the layer would actually experience due to consolidation or the layer under its' own weight. The time rate of settlement may be important in estimating the rate of leachate generation for the efficient design of leachate col- lection systems and in estimating the increase in stability during consolidation. 95 / / / Ir” 3, // ‘3 second lift 1’ F. / m l’,/ E sand X= 110 PCF 1:1“ X= 70. 9 PCF m c = 0. 289(1+eo) m g? wc = 270% I? first lift ,3 H0 = 10. 0 ft. ,3 U) U) Esand ______ i: 110 PSF 110 PSF 819 PSF 929 PSF ‘ 26.8 16.%: i 12. 8 10.3 819 psr 19 PSF 819 PSF 1638 psr L_I8.7 CB 33 + A? = Q €(%) Primary settlement H .. 6' _ ' S -So£dz 'EaveH - 17.3 inches Hf = HOf/Ho] X 25H] = 120in‘ (0.2925-0.2091) = 13.3 inches 0.754in Time for primary compression tp = T(Hp/2)2= (1)(120/g%_ =85 days to complete primary compression cv 0. 0295in /min Secondary settlement in 1 year HS = C.‘H log t/tp = 0.0187(120-17.3)log 365/85 = 1.2 inches Leachate released during primary compression 1 ft2 column 17.3in(1ft/12ih)= 1.44ft3/ft2 = 469,737 gal/acre (a) Figure 5.6 Settlement predictions for a 10 foot thick layer of sludge consolidating under the weight of another 10 foot layer (a) primary sludge (b) combined sludge. 96 AZ“ / / /’/' $1 // g second lift // 7’ / —-1 Esand x = 110 PCP-H: x= 69.2 PCF w0c=0.305(1+e0) a, . . gw = 318% .51 first lift 3H0: 10 ft. 3 m 01 8224109 ______ m 110 PSF 110 PSF 802 PSF 912 PSF , 2830 17.57; [-13.4 -10.9 802 PSF 802 PSF 802 PSF 1604 PSF L192 “’0 6;, + A? = 6'; E. (%) Primary settlement 5 =83, dz = EaveH = 18 inches AHf = ”Of/H01 xAH] = 120in. x(0.2045-0.1039) = 16 inches 0.754in Time for primary compression tp = WHO/2)2 = (1)(120/2)2 = 209 days to complete primary compression cv 0.0119in‘7min If 26.6% decomposition occurs tp = “Have/2)2 = (_1)(95.7/2)2 = 1.8 years to complete primary cv 0.00239inZ/min compression Secondary settlement in 1 year HS = C.(H log t/tp = 0.0244(120-18)log 365/209 = 0.6 inches Leachate released during primary compression 1 ft? column 18in(1ft/12in) = 1.5ft3/ft2 = 488,706 gal/acre (b) Figure 5.6 continued. 97 Decomposition of the organic fraction has been shown to greatly increase the time required for primary consolidation. Considering Figure 2.9, there would be additional settlement of the decomposing sludge under a constant overburden stress. For 26.6 percent decomposition, the con- solidated sludge layer would be expected to settle an additional 25 percent. The additional settlements for the examples presented in Fig— ures 5.5b and 5.6b would be 9.0 feet and 2.3 feet respectively. If this is taken into account in calculating the time required for primary com- pression, the times are about 20 years and 1.8 years for the examples in Figures 5.5b and 5.6b, respectively. 0. Landfill Stability(shear strength parameters) The highly fibrous nature of papermill sludges tends to make them respond to applied stresses in a plastic manner as shown in Figure 4.7. Typically, higher fiber contents result in higher initial strengths, and thus higher measured friction angles (Laza, 1971; Khattak, 1978). The amount of fiber in a primary papermill sludge is usually measured by ignition at high temperatures with the weight loss taken as the organic (fiber) fraction. Addition of biological solids from the sec- ondary treatment processes gives an increase in the organic fraction even though little, if any fiber has been added. Comparison of Figures 4.9 and 4.11 tend to support this. The friction angle for the primary sludge, measured at 63.4 degrees, decreased to 49 degrees upon addition of secondary sludge, while the organic fraction increased from 0.49 for the primary sludge to 0.58 for the combined sludge. Accompanying the decrease in the friction angle was an increase in the apparent cohesion from 0 kg/cm2 to 0.21 kg/cmz. Water content has been plotted against all around consolidation 98 pressure in Figures 4.9b and 4.11b for primary and combined sludge, respectively. The higher organic content of the combined sludge gives it a higher water content than the primary sludge at similar consolidation pressures. There was also a greater decrease in water content of the combined sludge for a given stress increment. Figures 4.9c and 4.11c summarize the test results in terms of total stresses by plotting undrained shear strength, cu, against consolidation pressure. The ratio cu/p appears to be a constant for both sludges which is typical of normally consolidated soils. The shear strength of the sludge, in terms of effective stresses, was also evaluated by consolidated-drained (CID) triaxial tests. Since drainage is permitted during load application, measured total stresses are equal to effective stresses. This test method eliminates the de- velopment of high pore pressures, but the problem of defining failure still exists. As shown in Figures 4.12a and 4.146 the axial stress continues to increase at strains greater than 20 percent. As with CIU tests, failure was taken at 20 percent axial strain, resulting in the kf lines in Figures 4.13 and 4.15 for primary and combined sludges, respectively. The friction angle of the primary sludge measured 33.2 degrees, while that of the combined sludge measured 23 degrees. These results are much lower than those obtained from 010 tests on the same sludge materials. The 3 values obtained from the two test methods are sunmarized along with data obtained by Khattak (1978) for model sludge materials in Figure 5.7. To illustrate the significance of these test results an example analysis of the stability of the landfill cross-section shown in Figure 5.8 has been performed. Figure 5.8 shows a possible Angle of internal friction, I , deg. 100 80 60 40 99 V7 030 tests data from Khattak (1978) O CID tests for model sludges V 030 test, primary A sludge ‘010 test, combined primary [3’ and secondary sludge CIU test, combined sludge ' V G with nutrients added . A-ct— CID test, primary slu 0 ”We" [3“ C10 test, combined CIU test, combined sludge sludge after 26.6% decomposition J l A ‘ L l A ‘ A g‘ 0 20 4O 60 80 100 Organic content (% by weight) Figure 5.7 Dependence of the angle of internal friction (3') on organic content for several sludge materials. 100 mummezm meapwmw mHnHmmog saw: muon mmusHm mensweg a mo :oHuummiumocu mHomem w.m mesoHI 1 1x11. .._ n H e NI I metf 8.2 n x 2 omeepm t 8 II: A N H a? MI 8.5 m mzwnmc n a C .5 8:80.. we .23ch O {\7 )1 101 cross-section along the perimeter of the landfill with a finished slope of 1 vertical to 2 horizontal. Also shown are the slices used to per- form the example slope stability analysis presented in Table 5.1. The center of the critical failure circle was determined using the me- ods outlined in NAVFAC DM-7 (1971). The Bishop (1954) simplified method of slices was used to evaluate the stability of the slope assum- ing two drainage conditions. The two drainage conditions considered were a slope in which excess pore pressures coincided with the surface and one in which no excess pore pressures were present. The first con- dition may be an extreme case in which no drainage of the sludge has occurred and the second case exemplifies the condition of a landfill with intermediate drainage layer conpletely relieving excess pore pressures. The results of several stability analyses for the various sludge conditions, test methods, and drainage conditions are summarized in Table 5.2. This comparison shows the influence of drainage conditions on landfill stability. Also shown is the greater dependence of overall stability on the material cohesion than on its friction angle. Due to the relatively low material weight, only a small portion of the frictional component of shearing resistance is mobilized. The results of several other stability analyses are presented in Appendix E. Little or no field data is available to support use of the results of either test method. The measured friction angles in the CIU test for both fresh sludges appear unreasonably high. Fibers extending across potential shear planes in triaxial test samples, which are able to withstand tensile forces, may be the cause for these high friction angles. In considering the long term stability of a landfill deposit, 102 mm.o n zumwmm mo gouumm A: on u > .pm om u xv L328 20...; mm.o n em.c n He.o n mNN.IN\OIN.NH n mIee :Nanw 88.8w SNNWN on.o NoH.o MNN.o HNo.m mem.m INN.N m 84H.H Imo.H IN8.N NeN.e ooo.m meo.N e NII.H Imm.H HIN.m mom.m Nme.m QON.H m HHN.N mmI.N wem.m HIN.H New.H mmN.H N mom.m eon.e NMN.H Nmm.o mHm.o ImN.o H 1 Hmm.ov HHm.oV HH.oV mIII MIII WISE mIII mIII mIIe mop.” mIII em $523-5 8:: 2.8 me: + 888 u x: MNN.mNumN Ice.o mom.o MNH.N No.Nm o Hmm.N N.mm m.m N m Nme.m ONN.N NI¢.IH 8N.He o wme.NN o.ONm c.8H ON I efle.e mHN.m mmm.oH ON.mN o oom.eN o.mNm a.IH oN m 4mm.e HmI.N wNe.N Im.N o NNN.oN o.ImN m.eH ON N Imm.H ome.o mmm.o- mo.e- o NNe.m o.om N.m 8H H :28: 3:35 8:; ~83 $.35: 48er Ge: 3: 3: 8.8. + 233.75 8.: men: 8 8 I I I e 8:8 33.5.6. 3on of S mvcoammtoo ; meme: :3» n a E .o n w .88 u. use 8.2 ... x 8838 .285 mmmammmmm ”Ice mmuuxm oz IHHI IIOIm < epmHeH mumzmmmIe IIoe mmmuxw 1:3 3on < co...— fifl 3.33m .55. PHIQ wsz: 33m macaw >522:— mom mHm>H._.H.:m<._.m H.m HES. 103 OO.O u NOONOO NO NOOOOO OO.m OO.O NN.O u NNN.ON\OOO.ONNu MOON Omgfluw OONNSuw 832".» NON.O NNO.O NOO.N ONO.O OOO.O NOO.H m ONO.OO ONO.NO ONN.NO NOO.N OOO.N ONO.H O NOO.OO NOO.OO NNN.OO ONO.N NON.” NNO.H N NHO.ON OOO.NN MOO.OO OOO.N OOO.N ONN.N N ONO.NH OOO.NN OON.NN OOO.O OOO.O OON.O N ON0.00 R0.00 XOO.NO mIJm mzau WIAu mzmm mzmm mImm wuwpm Ow + 233.75 1:: m5: ”:3 Me? + Mmou u x2 82an OOO.O NOO.N NNN.N NO.NO O NOO.N N.OO N.O N O NOO.OO OOO.NN NOO.ON ON.NO O OOO.NN O.ONN O.ON ON O ONO.NO OOO.ON OOO.ON ON.ON O OOO.ON O.ONN O.ON ON m NOO.OO NNN.ON ONO.N OO.N O NNN.ON O.OON AO.ON ON N NNO.HN NNO.O OOO.O- OO.O- O NNO.O O.OO N.m ON N OONNONNO ANONOFNO NOONNO NOOOO AONNmNNO OON\ONNV ANONMX AONV AOOO Om + 2333: 2-: wsm: x. 3 z < O O 82.0. 807. 3596 a .8» on; 323 :3» n O .o u w .oe.mm u w 68.. ads u E» 833m >852; AOV .28 Wm ”.55. 104 TABLE 5.2 SUMMARY OF STABILITY ANALYSES Sludge and Test 3 3 Factor of Safety * Condition (deg.) (psf) undrained drained slope slope Primary Sludge (5TH) 63.4 0 0.33 5.08 Combined Sludge (BTU) 49.0 430 1.37 4.31 Primary Sludge (CID) 33.2 238 0.75 2.44 Combined Sludge (CID) 23.0 231 0.70 1.89 Decomposed Sludge (5TH) 28.7 225 0.75 2.11 * A stable slope is normally assumed when the factor of safety is greater than 1.00. 105 these fibers may not be held tightly enough at low consolidation pres- sures to yield these high friction angles. In addition, possible de- composition involving disintegration of pulp fibers,as shown in Figures 5.2b and 5.3,may reduce or eliminate the fibers' contribution to the frictional component of shearing resistance. If this is the case, the friction angle of the sludge material may approach that of the mineral component. Khattak (1978) measured the friction angle of kaolinite to be approximately 20 degrees. A value of‘i = 28.7 degrees was measured for the combined sludge used in this research program following 26.6 percent decomposition. Figure 5.9 shows the effects of the addition of nutrients and decomposition on the deviator stress of combined sludge samples. Figure 5.10 summarizes the results of consolidated-undrained triaxial tests on the fresh combined sludge, the combined sludge after addition of nutrients, and after 26.6 percent decomposition. Table 5.2 shows the significance of decomposition on the factor of safety for the example slope considered in the calculations presented in Appendix E. Considering the difficulty in determining an appropriate value of 3 for the sludge, a somewhat conservative although realistic assess- ment of the landfill stability for design purposes may be obtained using the measured material cohesion and assuming a friction angle of 20 de- grees. For field deposits, insitu measurement of the shear strength by means of a field vane may be appropriate for current sludge strengths. 106 1.50 - 0 Combined sludge organic content = 58% strain rate = 0.0011 mm/sec- V Combined sludge with nutrients added strain rate = 0.0011 mm/sec Combined sludge g 0 after 26.6% strain rate = 0.006 mm/sec . 1.25 _ decomposition o o O 7 NE a o V V 15 ° v V 'x o f: 1.00 I- o O V V I6” ° v V I E? 9 Vvv o. 6 m 0 v 0 O ‘ g 0.75? o v o 0 ° - _ l}: o v 9 (0.1—03%“ L o s v° .ro O '6 g 4’ Consolidation pressure :2 0.50 - 9 0'3=1.0 kg/cm2 6! 7 lo 0! 0.25 .V o "6' 0 1 L n 1 L n I L j 1 0 2 4 6 8 10 12 14 16 18 20 Axial strain (%) Figure 5.9 Effect of decompositiog_gn deviator stress of combined sludge samples in the CIU test. 107 .mwmmn mmmcum m>wpummmm .mmcwp mx .mpmmp mexmwgp umcwmgccz-wmpmuwpomcou mo szEEOm oH.m mcamwu N55 .Nznb+ E u m OMIIPVNW ON .N O; OO O . v. . A W. O cowpwmoasoumu No.m~ Lmumm mmvaFm vmcwnsou Av cmcwm mucmwcuac cum: mug? 8:528 9 m6 Nmm u pcmpcoo umcmmco mug? 3:258 0 N53 :O u w .ONON up .OOO.ON u w O; l o NEU\mx o~.o n.w .oqw.o¢ n m .omH.mm u .m.H N830. NO 6 w .93.? u ... .ONONO u w. warm u MOS. L o.N Zulu/Bx ‘z/( Ely-L9) = _b_ CHAPTER VI SUMMARY AND CONSLUSIONS The sumnary and conslusions are presented in the areas of : (1) physical properties, (2) engineering properties, (3) decomposition effects on sludge properties and landfill performance, and (4) sugges- ted field instrumentation and monitoring. A. Physical Properties Physical properties of the papermill sludge were measured in order to better evaluate differences in engineering behavior of the sludge materials. Physical properties included water content, unit weight, organic content, specific gravity, and pH. These properties were influ- enced most by differences in the organic content. Higher organic con- tents of the combined sludge resulted in higher water contents (lower solids contents), lower unit weights and lower specific gravities. The pH of the sludge was influenced by pretreating agents used prior to de- watering, and pH changes served to indicate microbial activity. Decreased pH values were generally associated with activity of acid forming anae- robic bacteria. A reduction in the organic fraction was also observed for decomposing sludge samples. .8. EngineeringgProperties of the Sludges Stress deformation behavior of the sludge was observed in terms of the consolidation behavior and shear strength parameters of the sludge materials. One-dimensional consolidation tests utilizing a range of compressive 108 109 loads, from 0.1 to 10 kg/cmz, measured the sludge response to applied stress. The results, summarized in terms of strain versus pressure, showed that the combined sludge with its higher initial water content was more compressible than the primary sludge. Use of the compression index for prediction of ultimate settlements for two possible landfill configurations showed the combined sludge to be slightly more compres- sible than the primary sludge. Ultimate settlement estimates based on MacFarlane's (1969) method utilizing single increment load tests were less than those predicted using the compression index. The rate of consolidation, which is dependent on sludge permeabil- ity, was compared for the two sludges by means of the coefficient of consolidation. These results showed that the primary sludge would com- press approximately twice as rapidly as the combined sludge for typical field loading conditions. Estimates of the coefficient of consolidation, c were obtained from the Taylor square root of time construction for v9 each load increment during the consolidation test. These results also allowed indirect determination of the coefficient of permeability k. Over the range of applied loads (0.1 to 10 kg/cmz), k for the primary 5 to 8.0x10"9 cm/sec while k for the combined 9 sludge ranged from 2.5x10' ‘6 to 1.1x10' sludge varied from 1.3x10 cm/sec. Also, use of drainage layers at 10 foot intervals would decrease the theoretical time required for primary consolidation by a factor of 10 or more for the layer con- figurations discussed. Two variations to the standard consolidation test procedure included the single increment and rapid load increment (quick) proce- dures. Single load increment tests yielded results which differed from other test methods in some instances. Rapid load increment tests and 110 standard 24 hour increment tests gave nearly identical results. Shear strength of the fresh and partially decomposed sludge was measured by consolidated—undrained (ETD) and consolidated-drained (CID) triaxial tests. Stress-strain curves showed that large strains were required to fully mobilize the available sludge strength. This implies that unacceptably large deformations may occur before overall instability develops. Experimental data, summarized in terms of 6'- 6 plots provided the angle of internal friction and cohesion on an effective stress basis and water content and undrained strength versus all-around consolidation pressure. The 010 tests gave a friction angle for the fresh primary sludge equal to 63 degrees as compared to 49 degrees for the combined 2 for the combined sludge. However, a cohesion intercept of 0.21 kg/cm sludge gives it a slightly higher strength at low overburden pressures. The CID test yielded friction angles of 33 degrees and 23 degrees for the primary and combined sludges, respectively. Nutrients added to the combined sludge to aid decomposition lowered the 3 value from 49 degrees 'to about 40 degrees for the undrained tests. Decomposition of 27 percent lowered the friction angle from 40 degrees to about 29 degrees. Using these strength parameters, several stability analyses were performed on a typical slope for the undrained and drained conditions. Due to the low sludge unit weight the material cohesion was found to have more influence on stability than the friction angle. Also, the drainage condition was found to be the most important factor relative to stability of the example slopes. C. Decomposition Effects on Sludge Prpperties Decomposition of the sludge organic fraction reduces the amount and strength of interlocking fibers in a sludge mass. This decomposition 111 also generates various gases which may be effectively trapped in low permeability sludge. Decomposition of 27 percent lowered the cv value to 20 percent of its original value. This decrease in cv resulted in tripling the time required for completion of primary compression for the example configurations. In addition, 27 percent decomposition will re- sult in a 25 percent increase in settlement and will generate a similar amount of additional leachate. A reduction in sludge stability resulting from decomposition was difficult to determine accurately and may be dependent on the test method employed. Stability would be highly dependent on drainage conditions. A large decrease in permeability as a result of decomposition might effectively trap pore water and gas, thus altering the effective stress in the sludge mass. These factors may contribute to additional settle- ment, increased leachate generation, production of foul odors, and a reduction in shear strength and thus stability. 0. Suggested Field Instrumentation and Monitoring It is recommended that instrumentation be installed to monitor the behavior during construction and initial filling of a future landfill cell. The field observations can be used to select the best analysis methods. Settlement plates consisting of steel or aluminum plates with riser pipes could be installed at convenient elevations during sludge placement. The initial and subsequent elevations of the top of the riser pipes would be monitored to provide data on the landfill settle- ment. This information would be used to compare settlement estimates based on consolidation test results. Landfill settlements, tabulated over a period of time, would provide information on secondary compres- sion and effects of sludge decomposition. In addition, this data would 112 help evaluate the effectiveness of leachate collection systems. Pore pressure transducers installed at various elevations near the settlement plates could measure the reduction in pore pressures as con- solidation progresses. These devices could also indicate the point where pressures have decreased to a level sufficient to allow placement of an overlying lift of sludge without creating an unstable condition. The development of gas pressures, such as those observed in decomposing lab samples, could also be recorded at an early stage of decomposition. BIBLIOGRAPHY Alexander, J. A., Nardwell, R. E., and Charlie, H. A., "Gas Generation from Combined Papermill Sludges," Presented at the Northeast Regional Meeting, N. C. A. S. 1., Boston, Mass., 1978. Al-Khafaji, A. W. N., "Decomposition Effects on Engineering Properties of Fibrous Organic Soils," Unpublished Ph.D. Thesis, Michigan State University, East Lansing, Michigan, 1979. Al-Khafaji, A. N. N., and Andersland, 0. B., "Ignition Test for Soil Organic-Content Measurement," Journal of the Geotechnical Engineering Division, ASCE, Vol. 107, No. GT4, April, 1981. American Society for Testing and Materials, Book of ASTM Standards, Parts 11 and 15, Philadelphia, Pennsylvania. Andersland, 0. B., and Charlie, w. A., "A Cut Slope in Consolidated Papermill Sludge," Proceedings of the Conf. on Insitu Measurement of Soil Properties, Vol. 1, American Society of Civil Engineers, 1975. Andersland, 0. 8., Charlie, w. A., and Marshall, 0. N., Second Annual Report to the U.S. Environmental Protection Agency, Division of Engineering Research, Michigan State University, East Lansing, Michigan, 1973. Andersland, 0. B., Khattak, A. S., and Al-Khafaji, A. N. N., "Effect of Organic Material on Soil Shear Strength," in Laboratory Shear Strength of Soil, ASTM STP 740, R. N. Yong and F. C.'Townsend, eds., American Society for Testing and Materials, 1981. Andersland, 0. B. and Laza, R. N., "Permeability of High Ash Papermill Sludge,“ Journal of the Sanitary Engineering Division, ASCE, Vol. 98, No. 5A6. 00. 927-936, 1972. Andersland, 0. B., Vallee, R. P., and Armstrong, T. A., "An Experimental High Ash Papermill Sludge Landfill," First Annual Report to the U.S. Environmental Protection Agency, Division of Engineering Research Michigan State University, East Lansing, Michigan, 1972. Bishop, A” N.,"The Use of the Slip Circle in the Stability Analysis of Slopes," Geotechnique, London, 5:7-17, 1954. Bishop, A. N. and Henkel, D. J., The Measurement of Soil Properties in the Triaxial Test, Edward Arnold, Ltd., London, 1962. 113 114 Bowles, J. E., Engineering Properties of Soils and Their Measurement, McGraw-Hill, Inc., 1978. Charlie, N. A., Hardwell, R. E., and Andersland, O. B., "Leachate Generation from a Sludge Disposal Area," Journal of the Environmental Engineering Division, ASCE, Vol. 105, No. EES, Proc. Paper 14884, October, 1979, pp. 947-960. Charlie, N. A., Nardwell, R. E., and Cooper, S. R., "Engineering Properties of Combined Primary and Secondary Papermill Sludge," N. C. A. S. 1., Central-Lake-States Regional Meeting, Chicago, Ill., 1979. "Design Manual - Soil Mechanics, Foundations, and Earth Structures," NAVFAC DM-7, Mar., 1979, Naval Facilities Engineering Command, Department of the Navy, San Bruno, California. Eastman, J. A., Personal Communication, 1978 and 1980. Gibson, R. E. and Lo, K. Y., "A Theory of Consolidation for Soils Exhibiting Secondary Compression," Norwegian Geotechnical Institute, Publication 41, Oslo, Norway, 1961. Gillespie, N. J., Gellman, I. and Janes, R. L., "Utilization of High Ash Papermill Haste Solids," Proc. 2nd Mineral Haste Utilization Symposium, IITRI, Chicago, Ill., 1970. Gillespie, N. J., Mazzola, C. A., and Gellamn, 1., "Landfill Disposal of Papermill Haste Solids," Presented at the 7th Technical Association of the Pulp and Paper Industry Air and Water Conference, Minneapolis, Minn., June 7-10, 1970. Hanrahan, E. T.. "Investigation of Some Physical Properties of Peat," Geotechnique, 4:3:108-123, 1954. Khattak, A” S;."Mechanical Behavior of Fibrous Organic Soils," Unpublished Ph.D. Thesis, Michigan State University, East Lansing, Michigan, 1978. Lambe, T. N., "A Mechanistic Picture of Shear Strength in Clay," Proc. ASCE Res. Conf. on Shear Strength of Cohesive Soils, 1960. Laza, R. N., "Permeability and Shear Strength of Dewatered, High Ash Content Pulp and Papermill Sludge," Unpublished Ph.D. Thesis, Michigan State University, East Lansing, Michigan, 1971. Lea, N. D. and Brawner, C. 0,,"Highway Design and Construction over Peat Deposits in the Lower Mainland of British Columbia," Highway Res. Board, Res. Rec., No. 7, Washington, D.C., 1963. MacFarlane, I. C., ed., MuskeggEngineering Handbook, University of Toronto Press, 1969. McKinney, R. E., Microbiology for Sanitary Engineers, McGraw-Hill Book Co., Inc., 1962. 115 Miner, R. A. and Marshall, 0. W., "Biological Sludge Dewatering Practices in the Pulp and Paper Industry," Presented at the 13th Annual Purdue Industrial Waste Conference, 1975. Perloff, W. H. and Baron, W., Soil Mechanics Principles and Applications, Ronald Press, 1976. Perpich, W. M., "Design Considerations for Land Disposal of Paper and Pulpmill Sludge," T.A.P.P.I. Environmental Conference, Atlanta, Georgia, 1976. Perpich, W. M. and Zimmerman, E., "Major Components of Pulp and Papermill Residues," First Annual Conf. of Applied Res. and Prac. on Municipal and Industrial Waste, Madison, Wisconsin, Sept., 1978. Terzaghi, K., Theoretical Soil Mechanics, John Wiley and Sons, Inc., New York, 1943. Terzaghi, K. A. and Peck, R. 8., Soil Mechanics in Engineering Practice, 2nd ed., John Wiley and Sons, Inc., New York, 1967. Vallee, R. P., "A Field Consolidation Study of High Ash Papermill Sludge," Unpublished Ph.D. Thesis, Michigan State University, East Lansing, Michigan, 1973. Vallee, R. P. and Andersland, O. 8., "Field Consolidation of High Ash Papermill Sludge," Journal of the Geotechnical Engineering Div., ASCE, Vol. 100:GT3:309-327, 1974. Wahls, H. E., "Analysis of Primary and Secondary Consolidation," Journal of the Soil Mechanics and Found. Div., ASCE, 88§SM6:207-231, 1962. Wu, T. H., Soil Mechanics, Allyn and Bacon, Boston, 1976. APPENDIX A 116 TABLE A.1 WATER CONTENT OF SLUDGE SAMPLES Primary Sludge Combined Sludge 276% 271% 319% 316% 281% 278% 326% 337% 290% 279% 333% 318% 267% 252% 307% 316% 258% 274% 333% 314% 274% 267% 321% 295% 271% 269% 316% 308% 270% 276% 316% 309% 273% 32;: average = 318% average = 270% Values were measured in conjunction with other tests during the research program. TABLE A.2 COMPACTED UNIT WEIGHT 0F SLUDGE MATERIALS Volume of container = 0.100 cubic feet Primar Slud e Combined Slud e 5726 5714.5 5548 5640 wt. wet sludge + tare (gm) tare wt. (gm 2506 2507.0 2506 2506 sludge wt. (gm) 3220 3207.5 3142 3134 unit wet wt. (PCF) 71.0 70.7 69.3 69.1 average water content (%) 276 281 319 326 unit dry wt. (PCF) 18.9 18.6 16.5 16.2 TABLE A.3 ORGANIC CONTENT DETERMINATIONS Primary Sludge Combined Sludge 49.0% 49.0% 58.0% 54.0% 48.0% 59.0% 50.0% 48.0% 59.0% 47.9% 48.7% 59.0% 46.0% 48.0% 58.0% 49.0% 48.2% 57.4% 48.2% 57.5% average = 49.0% average = 58.0% 117 TABLE A.4 SPECIFIC GRAVITY OF SLUDGE MATERIALS Primary Sludge 1. Wt. flask + wgter + sludge 677.5 677.0 .686.10 2. Temperature, C 23.0 22.0 22.00 3. Wt. flask + water 673.4 673.4 680.60 4. Wt. evap. dish + dry sludge 274.9 273.7 277.85 5. Wt. evap. dish 266.3 266.2 266.30 6. Wt. dry sludge 8.6 7.5 11.55 7. Ww = 6 + 3 - 1 4.5 3.9 6.05 8. Gs = 6/7 1.91 1.92 1.91 average specific gravity = 1.91 Combined Sludge 1. Wt . flask + water + sludge 678.50 675.90 680.00 2. Temperature, C 25.00 25.00 22.00 3. Wt. flask + water 673.10 673.00 673.30 4. Wt. evap. dish + dry sludge 282.18 272.40 280.30 5. Wt. evap. dish 270.80 266.20 266.20 6. Wt. dry sludge 11.38 6.20 14.10 7. Ww = 6 + 3 - 1 5.98 3.30 7.40 8. GS = 6/7 1.90 1.88 1.90 average specific gravity = 1.89 .TABLE A.5 pH DETERMINATIONS 8/27/79 11/6/79 3/29/80 Primary Sludge 11.9 10.3, 8.6 9.7 Combined Sludge 11.9 8.3, 8.1 7.6 Sample procured on 8-27-79, pH measured at Nekoosa Papers Water Quality Center. Sample storage in sealed containers at 4°C. 118 TABLE A.6 DAILY MEASUREMENT OF SLUDGE PROPERTIES AT NEKOOSA PAPERS, 1979 February March Solids Content Ash Content Solids Content Ash Content % % % % 20 22 41 4O 26 24 55 45 26 22 55 36 22 24 36 46 27 25 54 4O 21 21 4O 43 24 22 48 44 22 25 44 48 24 23 47 42 23 24 43 42 43 20 79 4O 20 24 39 49 4O 23 81 44 20 26 45 48 36 22 72 44 20 22 39 42 22 22 38 42 21 22 45 41 20 21 37 38 26 20 45 39 20 24 32 43 26 22 47 32 21 22 38 38 22 26 32 38 18 22 39 44 25 23 4O 39 22 24 35 43 22 24 37 43 ave = 24 ave = 46 ave = ave = 42 June July Solids Content Ash Content Solids Content Ash Content % % % % 42 23 72 35 21 24 42 66 28 22 53 32 23 28 39 49 26 19 4O 34 -- 28 -- 44 24 23 33 37 -- 28 -- 40 26 24 38 38 —- 24 -- 39 26 22 40 29 28 22 50 4O 22 22 35 29 26 28 43 44 24 24 36 36 22 24 44 38 23 25 32 38 24 28 41 44 24 26 38 35 23 22 43 35 20 24 36 34 -- 20 —- 34 25 24 4O 35 24 29 43 49 25 24 41 4O 24 24 42 4O 20 24 31 41 22 26 37 48 22 20 28 36 24 29 47 57 ave = 24 ave = 37 ave. = 25 ave = 45 Source: Nekoosa Papers Inc. 0 Note: Solids content measured at 310 C for about 17 hours Ash content measured at 550 C for about 3 hours 119 TABLE A.6 cont. August Se tember Solids Content Ash Content . Solids Content Ash Content % % % % 24 34 42 59 22 22 41 45 26 32 4O 53 20 22 37 46 28 31 44 55 21 22 4O 36 34 22 66 36 30 21 55 46 24 27 38 38 24 26 55 57 24 24 39 38 26 22 48 43 26 20 45 34 29 27 68 45 32 24 52 50 23 27 67 64 36 24 61 43 24 18 58 34 34 23 65 44 -- 20 -- 43 31 26 64 50 -- 24 -- 50 30 25 53 49 28 24 54 49 31 22 48 39 26 23 33 47 26 22 62 43 28 24 54 48 31 26 66 45 24 26 49 50 22 37 ave = 24 ave = 49 ave = 27 ave = 48 October November Solids Content Ash Content Solids Content Ash Content % % % % 24 22 46 44 27 26 54 45 28 26 48 49 23 26 50 53 26 24 52 45 25 22 52 45 -- 26 -- 46 27 . 22 52 44 24 26 44 53 27 23 51 48 22 24 46 48 21 22 48 44 24 26 50 53 24 23 56 44 20 26 46 54 26 22 60 41 24 25 45 54 38 25 ' 73 47 24 28 54 45 29 24 60 48 24 28 46 57 3O 25 62 48 26 26 52 55 31 23 60 47 26 23 48 50 28 22 57 43 26 26 43 53 26 26 48 43 22 24 39 50 24' 28 41 51 21 39 ave. = ave = 51 TABLE A.6 cont. December Solids Content Ash Content % % 24 44 23 42 22 41 22 36 24 41 26 42 24 42 25 44 23 49 27 49 24 44 25 33 25 49 .2]. 2 ave. 24 44 120 APPENDIX B 121 Preparation of samples for decomposition Total Combined Sludge Sample Weight = 4500 grams water content = 309% 2 II II 1100 grams 3400 grams organic content = 58% organic material mineral material 638 grams 462 grams Approximate amount of carbon: 162 Cellulose C H 0 molecular weight 2 5 72 Carbon C 10 molecular weight 72/162 = 44.4% Cellulose contains about 44% carbon A small portion of the biological solids derived from secondary sludge would also contain carbon. Assume that the combined sludge contains 45% carbon 638 gms (0.45) = 287 grams of carbon in above sample Use a carbon to nitrogen ratio of 20 C/N = 20 = 287/20 = 14.36 grams of nitrogen Use a phosphorous to nitrogen ratio of 1/6 P/N = 1/6 = 14.36/6 = 2.39 grams of phosphorus Use a ratio of all other nutrient to nitrogen of 1/15 (all other)/N = 1/15 = 14.36/15 = 0.96 grams of all other nutrients 122 TABLE B.1 NUTRIENT PROPORTIONS FOR DECOMPOSING SLUDGE SAMPLES (Sodium Bicarbonate) Component Dry sludge solid NH4CI K2HP04 MgSO4 CaCl3 FBCIB'OHZO NaHCO3 Seeding Material C8 1 04 sure) 2 3 0 Nutrient Sour Nitrogen NH4C Phosphorous KZHP Magnesium MgSO (70% Calcium Chloride CaCl Iron FeCl pH Buffer NaHC 3 5 Percent of Desired Nutrient 1 26.19% 17.89% 20.2% 63.89% 20.66% 00.00% Wt. grams 1100. 54. 13. 70. 1255. Desired Weight 54.81 gms 13.36 gms 6.79 gms 1.50 gms 4.65 gms 5.70 gms % Dry Wt. 87.6 4.4 1.1 0.5 0.1 0.4 5.6 0.3 100.0 APPENDIX C 123 TABLE C.1 QUICK CONSOLIDATION TEST DATA Primary Sludge Q-Pl Initial dry density = 19.8 PCF Initial water content = 290% Dry sample weight = 27.0 grams Final water content = 107% Final dry density = 41.7 PCF ' time dial readig time dial readiz time dial readia (min) (in. x 103 (min), (in. x 10 3 (min) (in. x 10 load 0.1 kg/cm2 load 0.2 kg/cmz load 0.4 kg/cm2 0.0 0 0.0 0 0.0 0 0.1 61 0.1 46 0.1 93 0.25 133 0.25 69 0.25 142 0.5 195 0.5 92 0.5 199 1.0 278 1.0 123 1.0 268 2.0 380 2.0 155 2.0 346 4.0 456 4.0 185 4.0 415 8.0 500 8.0 213 8.0 467 1445.0 650 15.0 237 15.0 507 load 0.8 kg/cm2 load 1.6 kg/cm2 load 3.2 kg/cm2 0.0 O 0.0 0 0.0 O 0.1 112 0.1 109 0.1 98 0.25 170 0.25 167 0.25 153 0.5 232 0.5 231 0.5 210 1.0 313 1.0 315 1.0 291 2.0 408 2.0 416 2.0 396 4.0 494 4.0 521 4.0 509 8.0 557 8.0 607 8.0 612 15.0 601 13.0 641 15.0 679 16.0 604 unload 1.6 kg/cm2 unload 0.8 kg/cmz reload 1.6kg/cm2 0.0 0 0.0 0 0.0 0 0.1 29 0.1 21 0.1 22 0.25 35 0.25 27 0.25 26 0.5 41 0.5 35 0.5 30 1.0 48 1.0 47 1.0 35 2.0 54 2.0 60 2.0 43 4.0 60 4.0 74 4.0 48 8.0 62 8.0 87 8.0 52 15.0 64 15.0 95 15.0 55 30.0 56 TABLE C.1 Cont. 124 time dial readia time dial readin time dial readiag (min), (in. x 10 (min) (in. x 104 (min) (in. x 10 ) reload 3.2 kg/cm2 load 6.4 kg/cm2 load 10.0 kg/cm2 0.0 O 0.0 0 0.0 O 0.1 45 0.1 85 0.1 41 0.25 55 0.25 120 0.25 57 0.5 66 0.5 160 0.5 79 1.0 82 1.0 216 1.0 113 2.0 98 2.0 292 2.0 161 4.0 117 4.0 389 4.0 225 8.0 137 8.0 490 8.0 302 13.0 152 15.0 564 15.0 363 30.0 415 unload 3.2 kg/cmz 0.0 O 15.0 122 unload 0.4 kg/cm2 0.0 O 30.0 327 III! . 125 TABLE C.2 QUICK CONSOLIDATION TEST DATA Primary Sludge OOPZ Initial dry density = 18.2 PCF Initial water content = 274% Dry sample weight = 25.2 grams Final water content = 102.8% Final dry density = 42.6 PCF ' time dial reading time dial readiag time dial readin (min) (in.x 10 ) (min) (in. x 10 )7 (min) (in. x 10 I load 0.1 kg/cm2 - - ~load 0.2 kg/cmz load 0.4 kg/cmz F 0.0 0 0.0 O 0.0 0 T 0.1 265 0.1 80 0.1 90 0.25 337 0.25 130 0.25 123 0.5 410 0.5 184 0.5 178 1 1.0 514 1.0 256 1.0 252 R 2.0 642 2.0 347 2.0 344 ”r 4.0 773 4.0 437 4.0 437 8.0 855 8.0 510 8.0 517 load 0.8,gg/cm2 load 1.6 kg/cm2 load 3.2 kg/cmz 0.0 0 0.0 O 0.0 0 0.1 95 0.1 78 0.1 96 0.25 148 0.25 133 0.25 133 0.5 207 0.5 193 0.5 179 1.0 289 1.0 271 1.0 244 2.0 387 2.0 372 2.0 335 4.0 495 4.0 490 4.0 447 8.0 589 8.0 600 8.0 565 9.0 614 unload 1.6 kg/cm2 unload 0.8 kg/cm2 reload 1.6 kg/cm2 0.0 0 0.0 0 0.0 0 0.1 27 0.1 19 0.1 18 0.25 31 0.25 26 0.25 22 0.5 36 0.5 32 0.5 27 1.0 40 1.0 41 1.0 33 2.0 45 2.0 54 2.0 40 4.0 48 4.0 67 4.0 46 7.0 49 7.0 78 8.0 51 8.0 80 126 TABLE C.2 cont. time dial readin time dial readia time dial readia (min), (in. x 1041 (min) (in. x 10 3 (min) (in. x 10 reload 3.2 kgjcmz * * load 6.4 kgjcmz ' load 10.0 kg/cmz 0.0 0 0.0 0 0.0 O 0.1 38 0.1 66 0.25 42 0.25 48 0.25 92 0.5 60 0.5 59 0.5 122 1.0 88 1.0 76 1.0 166 2.0 130 r 2.0 99 2.0 229 4.0 188 4.0 130 4.0 309 8.0 262 l: 8.0 170 8.0 406 15.0 329 9.0 177 12.0 463 17.0 342 10.0 184 13.0 474 18.0 348 11.0 190 13.0 200 ' 14.0 205 15.0 210 unload 3.2 kg/cm2 unload 0.4 kg/cm2 0.0 0 0.0 0 12.0 100 17.0 246 127 TABLE C.3 CONVENTIONAL CONSOLIDATION TEST DATA Primary Sludge C-P1 Initial dry density = 18.5PCF Initial water content = 289% Dry sample weight = 24.15 grams Final water content = 107.5% Final dry density = 42.2 PCF ' time dial readin time dial readia time dial readin (min) (in. x 103 (min)_ (in. x 10 I (min), (in. x 10 load 0.1 kglcmz load 0.2 kgygaz load 0.4 kgygmz 0.0 0 0.0 O 0.0 O 0.1 70 0.1 50 0.1 141 0.25 132 0.25 64 0.25 196 0.5 190 0.5 77 0.5 264 1.0 255 1.0 92 1.0 344 2.0 321 2.0 110 2.0 440 4.0 366 4.0 126 4.0 525 8.0 393 11.0 151 10.0 606 609.0 625 17.0 160 16.0 636 35.0 176 30.0 666 60.0 191 60.0 695 120.0 210 125.0 726 190.0 223 264.0 759 446.0 254 351.0 771 641.0 266 472.0 780 1395.0 289 683.0 791 1425.0 804 load 0.8 kglcmz load 1.6 kg/cmz load 3.2 kg/cm2 0.0 0 0.0 0 0.0 0 0.1 127 0.1 146 0.1 181 0.25 193 0.25 202 0.25 264 0.5 255 0.5 253 0.5 345 1.0 313 1.0 304 1.0 439 2.0 373 2.0 366 2.0 567 4.0 401 4.0 452 4.0 710 8.0 414 12.0 584 9.0 837 15.0 423 15.0 595 15.0 900 30.0 431 34.0 619 30.0 970 84.0 444 76.0 640 60.0 1021 160.0 453 146.0 656 98.0 1053 392.0 473 227.0 668 239.0 1109 666.0 592 638.0 702 582.0 1156 777.0 604 1410.0 737 1424.0 1193 1490.0 635 1420.0 741 128 TABLE C.3 cont. time dial readig time dial readiag time dial readipg _(min), ,(in. x 10 3 (min) (in. x 10,), (min) (in. x 10 ) unload 1.6 kg/cm2 unload 0.8 kg/cm2 reload 1.6 kg/cm2 0.0 0 0.0 O 0.0 0 1444.0 48 1432.0 161 0.1 29 0.25 35 0.5 44 1.0 54 2.0 63 4.0 69 8.0 74 19.0 79 39.0 82 60.0 83 115.0 88 236.0 92 537.0 98 1440.0 103 reload 3.2 kg/cm2 load 6.4 kg/cm2 load 10.0 kg/cm2 0.0 O 0.0 O 0.0 0 0.1 40 0.1 106 0.1 33 0.25 52 0.25 152 0.25 44 0.5 64 0.5 204 0.5 57 1.0 76 1.0 277 1.0 75 2.0 87 2.0 373 2.0 99 4.0 96 4.0 497 4.0 130 8.0 103 8.0 636 9.0 173 15.0 111 15.0 707 15.0 202 33.0 119 36 0 770 30.0 241 60.0 127 63 O 798 60.0 277 139.0 140 92 0 812 115.0 307 227.0 149 123 O 819 227.0 338 431.0 165 271 0 838 1430.0 414 581.0 175 420 O 848 1430.0 201 508.0 852 1465.0 933 unload 3.2 kg/cm2 0.0 0 1420.0 108 129 TABLE C.4 SINGLE LOAD INCREMENT CONSOLIDATION TEST DATA Primary Sludge SI—PI Primary Sludge SI-P2 Initial dry density = 19.5 PCF Initial dry density = 18.5PCF Initial water content = 267% Initial water content = 285% Dry sample weight = 27.3 grams Dry sample weight = 25.6 grams Final water content = 194% Final water content = 171% Final dry density = 26.0 PCF Final dry density = 28.7 PCF load 0.1-0.4 kg/cm2 load 0.1-0.8 kg/cm2 time diaT reading time dial reading (min), (in.x104) (min) (in.x10 ) 0.0 O 0.0 O 0.1 154 0.1 249 0.25 222 0.25 423 0.5 301 0.5 572 1.0 407 1.0 770 2.0 539 2.0 1007 4.0 670 4.0 1242 8.0 769 8.0 1419 15.0 829 16.0 1523 30.0 879 30.0 1580 60.0 920 60.0 1628 120.0 956 134.0 1676 197.0 985 240.0 1709 384.0 1018 370.0 1732 525.0 1032 595.0 1756 1190.0 1066 1296.0 1791 1476.0 1079 1616.0 1802 1580.0 1082 2607.0 1107 130 TABLE C.4 cont. Primary Sludge SI-P3 Primary Sludge SI-P4 Initial dry density = 18.8 PCF Initial dry density = 20.1 PCF Initial water content = 284% Initial water content = 258% Dry sample weight = 26.3 grams Dry sample weight = 27.8 grams Final water content = 144% Final water content = 115% Final dry density = 34.2 PCF Final dry density = 39.6 PCF load 0.1-1.6 kg/cm2 load 0.1-3.2 kg/cm2 time dial reading time dial reading (minlp (in.x10 ) y(min) (in.x10 ) 0.0 0 0.0 0 0.1 552 0.1 545 0.25 750 0.25 838 0.5 955 0.5 943 1.0 1230 1.0 1230 2.0 1556 2.0 1599 4.0 1883 4.0 1994 8.0 2136 10.0 2427 15.0 2275 15.0 2555 30.0 2364 30.0 2693 60.0 2419 60.0 2771 120.0 2465 120.0 2824 225.0 2501 219.0 2859 355.0 2527 580.0 2904 580.0 2555 1149.0 2930 1281.0 2594 1605.0 2945 1597.0 2606 131 TABLE C.5 ,QUICK CONSOLIDATION TEST DATA Combined Sludge Q-PI Initial dry density = 16.7 PCF Initial water content = 333% Dry sample weight = 22.88 grams Final water content = 115.6% Final dry density = 39.5 PCF ' time dial rea ing time dial reading time dial reading (min) (in.x10 ) (min) (in.x10 ) (min) (in.x10 ) load 0.1 kg/cm2 load 0.2 kg/cm2 load 0.4 kg/cm2 0.0 0 0.0 0 0.0 0 1.0 348 0.1 38 0.1 160 2.0 378 0.25 54 0.25 270 4.0 398 0.5 76 0.5 360 8.0 406 1.0 95 1.0 460 15.0 409 2.0 111 2.0 635 30.0 413 4.0 118 4.0 845 70.0 421 8.0 125 8.0 980 759.0 445 15.0 133 15.0 1041 26.0 1080 30.0 1083 45.0 1113 load 0.8 kg/cm2 load 1.6 kg/cmz load 3.2 kg/cm2 0.0 0 0.0 O 0.0 O 0.1 92 0.1 74 0.1 88 0.25 138 0.25 112 0.25 126 0.5 187 0.5 152 0.5 168 1.0 249 1.0 209 1.0 227 2.0 334 2.0 285 2.0 304 4.0 431 4.0 380 4.0 404 8.0 528 8.0 504 8.0 523 15.0 603 _15.0 616 15.0 635 30.0 716 unload 1.6 kg/cm2 unload 0.8 kg/cmz reload 1.6 kg/cm2 0.0 0 0.0 O 0.0 O 0.1 27 0.1 12 0.1 13 0.25 33 0.25 16 0.25 16 0.5 39 0.5 21 0.5 19 1.0 46 1.0 27 1.0 23 2.0 53 2.0 36 2.0 27 4.0 61 4.0 47 4.0 32 8.0 66 8.0 60 8.0 37 15.0 69 15.0 71 15.0 41 132 TABLE C.5 cont. time dial reading time dial reading time dial reading (min) (in.x10 ) (min) (in.x10 ) (min) (in.x10 ) reload 3.2 kglcmz load 6.4 kg/cn2 load 10.0 kg/cmz 0.0 O 0.0 0 0.0 O 0.1 40 0.1 68 0.1 31 0.25 50 0.25 90 0.25 38 0.5 60 0.5 114 0.5 49 1.0 75 1.0 148 1.0 67 2.0 94 2.0 194 2.0 93 4.0 121 4.0 264 4.0 133 8.0 157 8.0 356 8.0 191 15.0 197 15.0 454 15.0 258 30.0 252 32.0 569 30.0 341 unload 3.2 kg/cm2 unload 0.4 kg/cm2 0.0 0 0.0 O 15.0 112 60.0 333 133 TABLE C.6 QUICK CONSOLIDATION TEST DATA Combined Sludge Q-P2 Initial dry density = 16.7 PCF Dry sample weight = 23.1 grams Final dry density = 41.8 PCF 316% Initial water content = = 106% Final water content time dial reading time dial reading time dial reading (min) (in.x104) (min) (in.x104) (min) (in.x104) load 0.1 kg/cm2 load 0.2 kg/cm2 load 0.4 kg/cm2 0.0 0 0.0 0 0.0 o 0.1 201 0.1 71 0.1 73 0.25 258 0.25 115 0.25 124 0.5 319 0.5 165 0.5 176 1.0 400 1.0 239 1.0 253 2.0 489 2.0 335 2.0 357 4.0 537 4.0 445 4.0 476 6.0 633 6.0 505 6.0 545 7.0 528 7.0 571 load 0.8 kg/cmz' load 1.6kg/cm2 load 3 2 kglcmz 0.0 0 0.0 0 0.0 o 0.1 74 0.1 64 0.1 54 0.25 122 0.25 106 0.25 81 0.5 176 0.5 154 0.5 114 1.0 254 1.0 220 1.0 161 2.0 359 2.0 313 2.0 233 4.0 490 4.0 440 4.0 331 6.0 572 8.0 586 8.0 462 8.0 627 10.0 635 12.0 547 9.0 648 12.0 672 15.0 594 14.0 703 21.0 664 25.0 701 unload 1.6 kg/cm2 unload 0.8kg/cm2 reload 1.6 kg/cm2 .O thI-‘OOOO oooomdmt—o O O U! OOOOOOOOU‘INO—I wNm-le-‘OOOO OOOOOOU‘INHO HO—l U1 134 TABLE C.6 cont. time dial reading time dial reading time dial reading (min) (in.x104) (min) (in.x104) (min) (in.x104)_ reload 3.2 k on2 load 6.4 kg/cm2 load 10.0 kg/cm2 0.0 0 0.0 O 0.0 O 0.1 24 0.1 36 0.1 18 0.25 31 0.25 51 0.25 23 0.5 40 0.5 67 0.5 29 1.0 51 1.0 89 1.0 40 2.0 69 2.0 124 2.0 56 4.0 93 4.0 175 4.0 81 8.0 126 8.0 250 8.0 122 16.0 172 15.0 337 15.0 173 26.0 203 28.0 436 37.0 267 31.0 217 42.0 498 69.0 330 35.0 227 61.0 551 71.0 333 40.0 237 63.0 555 41.0 239 unload 3.2 kg/cm2 unload 0.4 kg/cmz 0.0 O 0.0 0 41.0 110 51.0 242 Combined Sludge C-Cl 135 TABLE C.7 CONVENTIONAL CONSOLIDATION TEST DATA Initial dry density = 16.8 PCF Initial water content = 307% Dry sample weight = 23.3 grams Final water content = 106% Final dry density = 41.6 PCF ' time dial rea ing time dial reading time dial reading (min) (in.x10 )p (min) yjjn.x10 ) (min); (in.x10 ) load 0.1 kg/cm2 load 0.2kg/cm2 load 0.4 kg/cn2 0.0 O 0.0 0 0.0 O 0.1 176 0.1 47 0.1 48 0.25 233 0.25 69 0.25 69 0.5 296 0.5 92 0.5 92 1.0 382 1.0 123 1.0 124 2.0 488 2.0 159 2.0 163 4.0 587 4.0 198 4.0 207 8.0 659 8.0 235 8.0 252 15.0 704 15.0 267 15.0 290 30.0 741 30.0 299 30.0 333 683.0 863 60.0 332 60.0 373 120.0 364 120.0 414 240.0 399 291.0 467 667.0 455 703.0 523 1473.0 504 1440.0 568 load 0 8 kg/cn2 load 1.6 kg/cm2 load 3.2 kgjcmz 0.0 O 0.0 0 0.0 O 0.1 55 0.1 59 0.1 48 0.25 78 0.25 79 0.25 65 0.5 104 0.5 102 0.5 84 1.0 141 1.0 135 1.0 112 2.0 187 2.0 181 2.0 149 4.0 244 4.0 238 5.0 217 8.0 304 8.0 305 8.0 260 15.0 358 16.0 377 16.0 332 30.0 410 30.0 436 32.0 402 65.0 464 66.0 501 60.0 459 168.0 529 121.0 547 127.0 519 257.0 560 180.0 577 199.0 551 367.0 585 240.0 597 249.0 566 462.0 601 517.0 653 510.0 615 635.0 625 728.0 677 692.0 634 838.0 643 912.0 692 1459.0 678 1441.0 678 1453.0 720 136 TABLE C.7 cont. time dial reading time dial reading time dial reading (min) (in.x104) (min) (in.x104) (min) (in.x10 ) unload 1.6 kglcm2 unload 0.8 kg/cm2 reload 1.6 kg/cm2 0.0 O 0.0 0 0.0 O 0.1 15 0.1 10 0.1 7 0.25 18 0.25 12 0.25 10 0.5 21 0.5 15 0.5 13 1.0 24 1.0 18 1.0 17 2.0 29 2.0 23 2.0 22 4.0 34 5.0 31 4.0 27 11.0 41 12.0 39 8.0 32 15.0 43 20.0 44 15.0 35 30.0 47 81.0 57 30.0 38 137.0 55 188.0 63 65.0 40 258.0 58 443.0 71 128.0 43 678.0 61 648.0 76 241.0 46 1437.0 63 1458.0 84 652.0 50 1420.0 53 reload 3.2 kg/cm2 load 6.4 kg/cm2 load 10.0 kg/cm2 0.0 O 0.0 0 0.0 O 0.1 15 0.1 24 0.1 14 0.25 20 0.25 34 0.25 19 0.5 25 0.5 47 0.5 23 1.0 33 1.0 64 1.0 30 2.0 42 2.0 89 2.0 40 4.0 54 4.0 123 4.0 55 8.0 64 8.0 167 8.0 74 16.0 72 15.0 215 19.0 107 30.0 78 33.0 282 30 0 128 62.0 85 60.0 331 60 0 174 113.0 91 120 0 382 120 O 198 254.0 100 240 0 427 181 0 218 598.0 113 394.0 456 351 0 250 1450.0 129 620.0 483 587.0 274 1430.0 527 1425.0 306 unload 3.2 kg[cm2 unload 0.4 kg/cm2 0.0 0 0.0 0 1435.0 126 1450.0 325 137 TABLE C.8 SINGLE LOAD INCREMENT CONSOLIDATION TEST DATA Combined Sludge SI-CI Combined Sludge SI-C2 Initial dry density = 16.4 PCF Initial dry density = 16.4 PCF Initial water content = 333% Initial water content = 321% Dry sample weight = 22.9 grams Dry sample weight = 22.9 grams Final water content = 222% Final water content = 192% Final dry density = 23.1 PCF Final dry density = 26.4 PCF load 0.1-0.4 kg/cmz load 0.1-0.8 kg/cm2 time dial reading time dial readdng T (min) (in.x104) (min) (in.x10 ) a 0.0 O 0.0 0 0.1 175 0.1 286 0.25 250 0.25 409 0.5 336 0.5 542 1.0 452 1.0 729 2.0 601 2.0 969 4.0 760 4.0 1233 8.0 893 8.0 1462 15.0 988 15.0 1610 30.0 1063 30.0 1715 60.0 1121 63.0 1791 123.0 1174 120.0 1843 233.0 1219 252.0 1896 594.0 1282 353.0 1919 1163.0 1324 636.0 1957 1619.0 1351 1255.0 1990 1687.0 2013 138 TABLE C.8 cont. Combined Sludge SI-C3 Initial dry density = 16.1 PCF Initial water content = 321% Dry sample weight = 22.2 grams Final water content = 158% Final dry density = 30.9 PCF load 0.1-1.6 kgjcmz time dial readdng (min) (in.x10 ) 0.0 O 0.1 427 0.25 593 0.5 775 1.0 1009 2.0 1304 4.0 1638 8.0 1955 15.0 2184 30.0 2354 60.0 2459 120.0 2530 268.0 2591 368.0 2614 651.0 2649 1270.0 2680 1710.0 2700 Combined Sludge SI-C4 Initial dry density = 16.6 PCF Initial water content = 316% Dry sample weight - 23.2 grams Final water conten = 126% Final dry density 37.5 PCF llfi'l load 0.1-3.2 kg/cm2 time dial readdng . (min) (in.x10 ) I 0.0 0 0.1 496 0.25 714 0.5 934 6_ 1.0 1221 2.0 1573 4.0 1973 8.0 2371 15.0 2689 30.0 2969 60.0 3118 121.0 3216 353.0 3322 451.0 3342 1374.0 3413 1961.0 3436 APPENDIX D 139 TABLE 0.1 TRIAXIAL TEST DATA Primary Sludge CU-Pl Consolidation press. = 1.0 kg/cm2 Water contegt* = 144% Strain rate = 0.0067 cm/min Dry density = 30.9 PCF 5'1f = 1.715 kg/cm2 13’ = 100% 53f = 0.05 kg/cm2 Af = 0.57 uf = 0.95 kg/cm2 cu = 0.833 kg/cm2 cv = 1.8x10'4 cmZ/sec load displacement pore axial E} 273 pressure strain 1 2 2 (kg) (cm) (kchmz) (%1 (kg/cm ) (kg/cm ) 0.00" 0.0000 0.00 0.000 1.000 1.00 2.88 0.0889 0.09 0.195 1.108 0.91 9.30 0.1143 0.24 0.473 1.399 0.76 10.82 0.1270 0.32 0.612 1.422 0.68 11.90 0.1397 0.38 0.751 1.435 0.62 13.53 0.1651 0.45 1.029 1.474 0.55 14.61 0.2032 0.51 1.447 1.483 0.49 15.25 0.2388 0.57 1.836 1.463 0.43 16.77 0.3556 0.65 3.116 1.471 0.35 17.85 0.4572 0.70 4.229 1.479 0.30 18.61 0.5588 0.74 5.342 1.475 0.26 19.53 0.6883 0.78 6.760 1.476 0.22 20.28 0.7645 0.80 7.595 1.493 0.20 20.99 0.9119 0.82 9.209 1.495 0.18 21.21 1.0109 0.85 10.294 1.463 0.15 22.56 1.1684 0.88 12.018 1.489 0.12 23.70 1.3487 0.90 13.994 1.506 0.10 24.78 1.4732 0.91 15.356 1.537 0.09 26.51 1.6256 0.92 17,026 1.598 0.08 30.91 1.9050 0.95 20.086 1.715 0.05 * water content and dry density after consolidation 140 TABLE 0.2 TRIAXIAL TEST DATA Primary Sludge CU-P2 Consolidation press. = 1.0 kg/cm2 Strain rate = 0.0075 cm/min Water content* = 148% Dry density* = 30.9 PCF 5'11. = 1.598 kg/cm2 5 = 100% 6'3. = 0.10 kg/cmz Af = 0.60 uf = 0.90 kg/cm2 cu = 0.749 kg/cm2 cv = 9.5x10'5 cm2/sec load diSplacement pore axial 5'1 5'3 pressure strain 2 (kg) (cm) (kg/c012) (%) (kg/cm ) (kg/cm?) 0.00 0.0000 0.00 0.000 1.000 1.00 1.18 0.0127 0.02 0.141 1.065 0.98 6.77 0.0381 0.19 0.424 1.294 0.81 9.05 0.0508 0.27 0.565 1.376 0.73 11.31 0.0711 0.37 0.792 1.435 0.67 12.61 0.0914 0.41 1.018 1.486 0.59 15.04 0.1727 0.53 1.922 1.529 0.47 16.28 0.2794 0.60 3.053 1.533 0.40 17.26 0.3759 0.65 4.183 1.537 0.35 18.23 0.4826 0.70 5.371 1.539 0.30 18.77 0.6096 0.74 6.784 1.516 0.26 19.42 0.6985 0.76 7.773 1.526 0.24 20.39 0.8331 0.80 9.271 1.529 0.20 20.83 0.9093 0.80 10.119 1.544 0.20 21.37 1.0109 0.81 11.250 1.552 0.19 22.07 1.0871 0.83 12.098 1.563 0.17 ' 22.83 1.2548 0.86 13.964 1.550 0.14 23.80 1.4046 0.88 15.631 1.562 0.12 24.56 1.5697 0.90 17.469 1.555 0.10 26.08 1.7983 0.90 20.012 1.598 0.10 * water content and dry density after consolidation 141 TABLE 0.3 TRIAXIAL TEST DATA Primary Sludge CU-P3 Consolidation press. = 2.5 kg/cm2 Water contedt* = 116% Strain rate = 0.0070 cm/min Dry density = 37.1 PCF Fr“. = 4.259 kg/cm2 '8‘ = 100% 5'31. = 0.04 kg/cm2 4,. = 0.58 uf = 2.46 kg/cm2 cu = 2.110 kg/cm2 cv = 6.9x10"5 cmzlsec load displacement pore axial ET} 273 pressuge strain 2 2 (k9) Ian) 1k9/cm 1 L70 (Igjcm ) (kg/cm L 0.000 0.0000 0.00 0.000 2.500 2.50 1.504 0.0203 0.03 0.242 2.590 2.47 5.410 0.0330 0.15 0.393 2.782 2.35 10.008 0.0406 0.27 0.483 3.028 2.23 14.119 0.0508 0.42 0.604 3.205 2.08 22.666 0.0737 0.77 0.876 3.531 1.73 25.858 0.0940 1.01 1.118 3.540 1.49 31.376 0.1448 1.30 1.722 3.762 1.20 33.540 0.1778 1.47 2.114 3.662 1.03 35.920 0.2591 1.67 3.081 3.621 0.83 38.625 0.3734 1.83 4.440 3.629 0.67 40.897 0.4699 2.00 5.587 3.595 0.50 42.304 0.5588 2.09 6.645 3.576 0.41 44.251 0.7112 2.16 8.457 3.587 0.34 46.739 0.8890 2.26 10.571 3.591 0.24 48.903 1.0414 2.32 12.383 3.615 0.18 52.582 1.2065 2.36 14.346 3.751 0.14 55.828 1.3462 2.39 16.007 3.869 0.11 60.805 1.5138 2.43 18.001 4.067 0.07 65.781 1.6815 2.46 19.994 4.259 0.04 * water content and dry density after consolidation 142 TABLE 0.4 TRIAXIAL TEST DATA Primary Sludge CU-P4 Consolidation press. = 2.5 kg/cm2 Water contedt* = 118% Strain rate = 0.0071 cm/min Dry density = 36.6 PCF ("711; = 3.968 kg/cm2 8‘ = 98% 5+3. = 0.035 kg/cm2 Af = 0.62 u1. = 2.465 kg/cm2 cu = 1.976 kg/cm2 cv = 5.3x10'5 cm2/sec load displacement pore axial ET} 223 pressure strain (kg) (cm) (kg/cmzl 1%) Lkgjcmz) (kg/cmz) 0.00 0.0000 0.00 0.000 2.500 2.50 1.75 0.0406 0.04 0.142 2.602 2.46 6.27 0.0584 0.14 0.508 2.868 2.36 13.31 0.0787 0.36 1.077 3.217 2.14 17.52 0.0914 0.57 1.415 3.345 1.93 24.12 0.1245 0.93 1.941 3.511 1.57 28.75 0.1702 1.25 2.300 3.550 1.25 32.63 0.2565 1.55 3.000 3.534 0.95 35.22 0.3429 1.74 4.004 3.520 0.76 36.97 0.4293 1.83 5.013 3.537 0.67 38.36 0.5131 1.95 5.992 3.494 0.55 39.56 0.6147 2.06 7.178 3.438 0.44 40.85 0.6833 2.10 7.979 3.470 0.40 43.63 0.8788 2.22 10.263 3.477 0.28 47.32 1.0871 2.30 12.696 3.573 0.20 48.62 1.1836 2.35 13.823 3.571 0.15 50.28 1.2852 2.39 15.010 3.599 0.11 54.72 1.4884 2.43 17.382 3.761 0.07 60.08 1.6993 2.46 19.844 3.972 0.04 61.00 1.7297 2.47 20.200 4.005 0.03 * water content and dry density after consolidation 143 TABLE 0.5 TRIAXIAL TEST DATA Combined Sludge CU-Cl * Consolidation press. = 0.92 kg/cm2 Water content = 165% Strain rate = 0.0066 cm/min Dry density = 29.0 PCF ‘6'” = 1.351 kg/cm2 ‘8 = 100% 63f = 0.03 kg/cmz A1. = 0.67 uf = 0.89 kg/cmz cu = 0.661 kg/cm2 cv = 3.2x10'S cm2/sec load displacement pore axial 5'1 5’3 pressure strain 2 2 1kg) (cm) (kg/cm?) 4%) (5.1/cm ) (kg/cm ) . 0.00 0.0000 0.00 0.000 0.920 0.92 0.98 0.0152 0.01 0.210 0.984 0.91 3.68 0.0330 0.10 0.443 1.098 0.82 6.19 0.0533 0.19 0.701 1.197 0.73 7.77 0.0737 0.26 0.969 1.244 0.66 9.79 0.1219 0.35 1.602 1.302 0.57 10.71 0.1600 0.43 2.091 1.286 0.49 11.90 0.2235 0.48 2.935 1.317 0.44 12.93 0.2870 0.53 3.803 1.335 0.39 13.47 0.3505 0.57 4.624 1.326 0.35 14.01 0.4140 0.60 5.476 1.326 0.32 14.82 0.5410 0.66 6.975 1.307 0.26 15.36 0.6045 0.69 7.796 1.306 0.23 16.07 0.7315 0.73 9.405 1.295 0.19 16.72 0.8585 0.76 11.047 1.289 0.16 17.47 0.9982 0.80 12.877 1.276 0.12 18.56 1.1760 0.81 14.913 1.309 0.11 19.64 1.3411 0.86 16.964 1.298 0.06 21.21 1.5316 0.88 19.332 1.339 0.04 21.80 1.5723 ”0.89 20.199 1.351 0.03 * water content and dry density after consolidation TABLE 0.6 TRIAXIAL TEST DATA Combined Sludge CU-C2 144 * Consolidation press. = 1.75 kg/cm2 Water contedt = 142% Strain rate = 0.0063 cm/min Dry density = 33.7 PCF '63, = 2.140 kg/cm2 '8' = 98% 5—3, = 0.14 kg/cmz A. = 0.81 uf = 1.61 kg/cm2 cu = 1.000 kg/cm2 cv = 3.7x10'5 cm2/sec load displacement pore axial E21 573 pressuEe strain 2 2 (kg) 19m) (kglcm 1. (%) (kg/cm ) (kg/cm ) 0.00 0.0000 0.00 0.000 1.750 1.75 0.39 0.0254 0.02 0.358 1.763 1.73 1.47 0.0457 0.06 0.634 1.813 1.69 4.00 0.0635 0.14 0.875 1.944 1.61 6.32 0.0762 0.20 1.055 2.076 1.55 9.36 0.1016 0.34 1.454 2.186 1.41 12.77 0.1397 0.55 1.952 2.253 1.20 14.71 0.1778 0.63 2.425 2.328 1.12 16.12 0.2159 0.72 2.940 2.347 1.03 17.47 0.2794 0.76 3.882 2.403 0.99 19.37 0.3810 0.98 5.389 2.312 0.77 20.94 0.4826 1.13 6.728 2.263 0.62 21.91 0.5842 1.20 8.035 2.245 0.55 22.61 0.6604 1.27 9.047 2.211 0.48 23.59 0.7874 1.33 10.844 2.190 0.42 25.10 0.9500 1.40 13.000 2.188 0.35 25.86 1.0465 1.46 14.780 2.144 0.29 27.70 1.2598 1.55 17.311 2.127 0.20 29.54 1.4351 1.61 19.761 2.134 0.14 30.19 1.5037 1.61 20.659 2.155 0.14 * water content and dry density after consolidation 3"“:- l ..- 145 TABLE 0.7 TRIAXIAL TEST DATA Combined Sludge CU-C3 * Consolidation press. = 2.5 kg/cm2 Water content = 126% Strain rate = 0.0062 cm/min Dry density* = 35.8 PCF Eiif.= 3.103 kg/cm2 §'= 100% 6+" = 0.275 kg/cm2 4, = 0.79 of = 2.225 kg/cmz cu = 1.414 kg/cm2 cv = 2.5x10"5 cm2/sec load displacement pore axial 5'1 5‘3 pressure strain 2 2 (kg) (cm) (kglcmz) (%) (kg/cmO) (kg/cm ) 0.00 0.0000 0.00 0.000 2.500 2.50 0.83 0.0457 0.03 0.228 2.543 2.47 2.08 0.0813 0.09 0.578 2.592 2.41 5.48 0.1270 0.21 0.879 2.769 2.29 10.98 0.1473 0.38 1.213 3.077 2.12 15.96 0.1727 0.55 1.630 3.335 1.95 20.77 0.2108 0.90 2.215 3.393 1.60 23.80 0.2616 1.08 2.950 3.459 1.42 25.75 0.3124 1.32 3.685 3.369 1.18 27.70 0.3759 1.36 4.553 3.473 1.14 28.56 0.4267 1.45 5.255 3.438 1.05 30.40 0.5537 1.59 6.925 3.407 0.91 31.38 0.6426 1.96 8.127 3.084 0.54 33.22 0.7188 1.85 10.466 3.275 0.65 33.76 0.8712 1.89 11.301 3.252 0.61 34.30 0.9601 1.95 12.470 3.199 0.55 36.03 1.1125 2.04 14.391 3.182 0.46 37.22 1.2649 2.12 16.479 3.123 0.38 39.27 1.4427 2.20 18.817 3.114 0.30 40.46 1.5723 2.23 20.571 3.106 0.27 * water content and dry density after consolidation 146 TABLE 0.8 TRIAXIAL TEST DATA Primary Sludge CD-Pl Consolidation press. = 1.0 kg/cm2 Water content* = 149% Strain rate = 5.4x10-4 cm/min Dry density* = 32.1PCF arlf = 2.452 kg/cm2 cv = 6.3x10’5 cmzlsec Ei3f = 1.0 kg/cm2 Volume after consolidation =123.93 cm3 load displacment pore axial 271 2%: pressu e strain 2 2 1kg) (cm) (kg/cm ) (%) (kg/cm ) (kgjcm 1 0.000 0.0000 0.00 0.000 1.000 1.00 0.887 0.0114 0.10 0.143 1.063 1.00 2.543 0.0254 0.30 0.297 1.182 1.00 3.516 0.0356 0.40 0.417 1.252 1.00 7.076 0.0597 0.70 0.674 1.506 1.00 8.288 0.0864 1.10 0.976 1.593 1.00 15.309 0.1118 1.40 1.245 2.095 1.00 7.786 0.1524 2.00 1.734 1.555 1.00 8.482 0.1778 2.30 2.021 1.606 1.00 9.683 0.2489 3.30 2.881 1.692 1.00 12.496 0.3708 4.80 4.294 1.891 1.00 15.580 0.5410 6.80 6.098 2.108 1.00 17.473 0.6553 8.20 7.385 2.241 1.00 21.044 0.8331 10.20 9.399 2.488 1.00 22.396 0.9220 11.20 10.462 2.578 1.00 28.022 1.1938 13.90 13.147 2.963 1.00 30.943 1.3462 15.40 14.826 3.155 1.00 32.999 1.4834 17.00 16.434 3.288 1.00 37.543 1.6434 18.50 18.182 3.585 1.00 41.763 1.8009 19.90 20.001 3.850 1.00 * water content and dry density after consolidation 147 TABLE 0.9 TRIAXIAL TEST DATA Primary Sludge CD-P2 Consolidation press. = 2.5 kg/cm2 Water content* = 120% Strain rate = 5.2x10-4 cm/min Dry density * = 38.2 PCF a—lf = 3.984 kg/cmz cv = 6.4x10 '5 cmzlsec 5'31, = 2.5 kg/cm2 Volume after consolidatidn = 97.07 cm load displacement pore axial E71 E73 £7 pressuEe strain 2 :2, (kg) (cm) (kg/cm ) (in (kg/cm ) (kg/cm?) 3 H 0.00 0.0000 0.00 0.000 2.500 2.50 ' 0.90 0.0102 0.20 0.125 2.572 2.50 52 4.21 0.0254 0.40 0.323 2.837 2.50 8.31 0.0381 0.50 0.481 3.165 2.50 12.12 0.0777 1.07 1.000 3.471 2.50 15.47 0.1245 1.40 1.574 3.737 2.50 16.23 0.1905 2.35 2.476 3.798 2.50 20.29 0.2718 3.40 3.579 4.123 2.50 23.59 0.3496 4.17 4.500 4.384 2.50 31.27 0.5131 6.20 6.582 4.998 2.50 35.92 0.6350 7.65 8.148 5.367 2.50 41.98 0.7620 9.05 9.745 5.884 2.50 45.66 0.8738 10.30 11.279 6.127 2.50 51.93 0.9906 11.50 12.749 6.614 2.50 58.21 1.0877 12.52 14.000 7.100 2.50 67.30 1.2853 14.40 16.215 7.799 2.50 70.97 1.3462 15.05 16.934 8.084 2.50 75.74 1.4478 16.10 18.292 8.438 2.50 78.33 1.5062 16.75 19.091 8.630 2.50 83.09 1.5850 17.55 20.130 8.984 2.50 * water content and dry density after consolidation 148 TABLE 0.10 TRIAXIAL TEST DATA Combined Sludge CD-Cl Consolidation press. = 1.0 kg/cm2 Water content* = 183% Strain rate = 3.99x10-4 cm/min Dry density* = 27.2 PCF Erlf = 2.452 kg/cm2 cv = 4.6x10'5 cmZ/sec E23f.= 1.0 kg/cm2 Volume after consolidation = 114.70 cm3 load displacement pore axial 571 E73 pressuEe strain 2 2 (kg) (cm) (kg/cm ) 110 (kg/cm ) (kglcm ) 0.00 0.0000 0 00 0.000 1.000 1.00 0.89 0.0254 0.20 0.183 1.063 1.00 1.62 0.0470 0.50 0.446 1.115 1.00 2.12 0.0660 0.80 0.688 1.150 1.00 2.85 0.1046 1.20 1.147 1.201 1.00 3.26 0.1270 1.60 1.445 1.231 1.00 3.55 0.1613 2.10 1.888 1.251 1.00 4.34 0.2600 3.40 3.200 1.307 1.00 5.99 0.3734 5.10 4.654 1.423 1.00 6.73 0.4293 5.80 5.372 1.475 1.00 7.86 0.5639 7.60 6.915 1.555 1.00 10.35 0.7637 10.20 9.400 1.729 1.00 12.20 0.9246 12.00 11.467 1.854 1.00 12.76 0.9804 12.70 11.972 1.894 1.00 13.68 1.0503 13.50 12.888 1.957 1.00 14.51 1.1278 14.40 13.729 2.014 1.00 15.90 1.2459 15.90 15.256 2.108 1.00 18.12 1.3973 17.70 17.200 2.256 1.00 20.15 1.5481 19.00 18.923 2.387 1.00 21.17 1.6248 19.95 20.000 2.452 1.00 * water content and dry density after consolidation TABLE 0.11 TRIAXIAL TEST DATA Combined Sludge CD-C2 Consolidation press. = 1.75 kg/cm2 149 Water content* = 166% Strain rate = 2.2x10'4 cm/min Dry density* = 30.9 PCF 0'11. = 4.76 kg/cmz cv = 2.7x10'5 cmzlsec crgf = 1.75 kg/cm2 Volume after consolidatidn = 98888 cm load displacement pore axial €71 crg pressu e strain (kg) (cm) (kg/cm ) (%) (kg/cm?) (kg/cm?) 0.00 0.0000 0.00 0.000 1.750 1.75 0.10 0.0127 0.15 0.095 1.758 1.75 0.29 0.0229 0.40 0.229 1.774 1.75 0.76 0.0610 1.30 0.689 1.811 1.75 1.21 0.0965 2.10 1.127 1.849 1.75 1.42 0.1067 2.30 1.236 1.865 1.75 3.81 0.2159 4.45 2.241 2.064 1.75 4.39 0.2515 5.15 3.130 2.112 1.75 5.32 0.2997 6.10 3.800 2.190 1.75 7.79 0.3912 7.50 4.938 2.395 1.75 10.71 0.5258 9.30 6.419 2.641 1.75 13.63 0.6629 11.10 8.133 2.886 1.75 14.82 0.7442 12.30 9.224 2.988 1.75 17.96 0.8738 13.90 10.752 3.252 1.75 20.39 0.9931 15.70 12.279 3.463 1.75 21.53 1.0732 16.40 12.996 3.559 1.75 25.97 1.2370 18.10 14.867 3.929 1.75 28.24 1.3894 20.00 16.893 4.119 1.75 33.22 1.5443 21.45 18.763 4.525 1.75 36.03 1.6535 22.70 20.088 4.760 1.75 * water content and dry density after consolidation 150 TABLE 0.12 TRIAXIAL TEST DATA Combined Sludge CD-C3 Consolidation press. 8 2.5 kg/cm2 cm/min Strain rate = 3.45x10-4 c‘rlf = 5.889 kg/cmz 5‘31,- = 2.5 kg/cm2 Water content* = 141% Dry density* = 35.1 PCF cv = 4.4x10’5 cmzlsec Volume after consolidation 3 = 87.57 cm load displacement pore axial 0’1 0'3 pressuEe strain 2 2 4kg) (cm) (kg/cm 1 (%1 Jkchm ) 1kglcm ) 0.00 0.0000 0.00 0.000 2.500 2.50 0.10 0.0076 0.00 0.112 2.508 2.50 0.51 0.0490 0.60 0.673 2.544 2.50 0.70 0.0635 0.80 0.863 2.560 2.50 1.08 0.0813 1.00 1.116 2.592 2.50 1.48 0.1041 1.40 1.403 2.626 2.50 3.98 0.1512 1.93 2.000 2.838 2.50 7.23 0.2296 2.89 3.000 3.107 2.50 11.14 0.3150 4.20 4.382 3.424 2.50 13.04 0.3975 5.30 5.548 3.569 2.50 15.31 0.4890 6.50 6.631 3.742 2.50 19.10 0.5982 7.70 8.075 4.207 2.50 22.72 0.7562 9.37 10.000 4.280 2.50 26.07 0.8382 10.25 11.259 4.519 2.50 29.97 0.9831 11.56 13.000 4.777 2.50 33.11 1.0770 12.70 14.362 4.979 2.50 38.52 1.2099 13.79 16.000 5.332 2.50 42.09 1.3824 15.00 17.316 5.550 2.50 45.33 1.4313 16.00 18.875 5.727 2.50 48.25 1.5124 16.73 20.000 5.889 2.50 * water conent and dry density after consolidation 151 TABLE 0.13 TRIAXIAL TEST DATA Combined Sludge with Nutrients CU-CNI Consolidation press. = 1.0 kg/cm2 Water content* = 163% Strain rate 0.0065 cm/min Dry density* = 29.9 PCF 611. = 1.224 kg/cm2 '8 = 100% 6-3f = 0.07 kg/cm2 A. = 0.81 uf = 0.93 kg/cm2 cu = 0.577 kg/cm2 - 4.3x10'5 cm2/sec O I load displacement pore axial 551 C73 pressuEe strain 2 2 1kg) 1cm) (kg/cm 1 1%) (kg/cm ) (kg/cm 1 0.00 0.0000 0.00 0.000 1.000 1.00 0.40 0.0178 0.03 0.032 1.002 0.97 1.19 0.0279 0.07 0.096 1.026 0.93 3.54 0.0508 0.15 0.284 1.134 0.85 5.41 0.0762 0.26 0.433 1.172 0.74 6.56 0.1016 0.33 0.522 1.192 0.67 7.68 0.1397 0.41 0.609 1.199 0.59 8.66 0.1778 0.46 0.683 1.223 0.54 9.31 0.2286 0.51 0.729 1.219 0.49 10.22 0.3048 0.57 0.794 1.224 0.43 10.87 0.3937 0.63 0.834 1.204 0.37 11.79 0.5334 0.69 0.891 1.201 0.31 12.33 0.6172 0.73 0.920 1.190 0.27 12.71 0.7112 0.76 0.936 1.176 0.24 13.52 0.8636 0.80 0.975 1.175 0.20 14.23 1.0414 0.84 1.006 1.166 0.16 15.09 1.1938 0.88 1.045 1.165 0.12 15.90 1.3462 0.90 1.078 1.178 0.10 16.82 1.4859 0.91 1.114 1.204 0.09 18.07 1.6764 0.93 1.162 1.232 0.08 * water content and dry density after consolidation ' .-__' Combined Sludge with Nutrients CU-CNZ Consolidation press. Strain rate 152 TABLE 0.14 TRIAXIAL TEST DATA = 0.0063 cm/min = 1.75 kg/cm2 Water content* = 139% Dry density* = 34.2 PCF crlf.= 1.968 kg/cm2 8': 100% 63f = 0.235 kg/cmz A1. = 0.87 uf = 1.515 kg/cm2 cu = 0.867 kg/cm2 cv = 2.7x10"5 cmzlsec load displacement pore axial 5'1 5’3 pressuEe strain 2 2 (k91_ .19m) 1 kglcm) (%) (kg/cm ) (191cm 1__ 0.00 0.0000 0.00 0 000 1.750 1.75 0.23 0 0127 0.02 0.170 1.751 1.73 0.68 0.0305 0.06 0.346 1.752 1.69 2.33 -0.0508 0.11 0.585 1.850 1.64 5.99 0.0762 0.21 0.909 2.081 1.54 9.23 0.1041 0.38 1.298 2.198 1.37 12.33 0.1524 0.56 1.938 2.291 1.19 13.74 0.1905 0.68 2.514 2.289 1.07 14.61 0.2311 0.80 3 107 2.238 0.95 15.26 0 2794 0.88 3.790 2.206 0.87 16.07 0.3429 0.97 4.663 2.174 0.78 16.88 0.4191 1.07 5.667 2.129 0.68 17.91 0.5461 1.18 7.298 2.081 0.57 18.83 0.6731 1.28 9.043 2.029 0.47 20.02 0.8661 1.38 11.611 1.980 0.37 20.72 1.0160 1.42 13.587 1.960 0.33 21.69 1.1786 1.47 15.629 1.946 0.28 22.45 1.3208 1.49 17.440 1.947 0.26 23.10 1.3970 1.50 18.510 1.963 0.25 23.91 1.5240 1.52 20.404 1.962 0.23 * water content and dry density after consolidation ..a "a Combined Sludge with Nutrients CU-CN3 153 TABLE 0.15 TRIAXIAL TEST DATA Consolidation press. = 2.5 kg/cm2 Water content* = 126% Strain rate = 0.0060 cm/min Dry density* = 35.1 PCF 6” = 2.566 kg/cm2 '3' = 100% 6—3f = 0.35 kg/cmz Af = 0.97 uf = 2.15 gk/cmz cu = 1.108 kg/cm2 cv = 2.8x10"5 cmzlsec load displacement pore axial 5‘1 5'3 pressuEe strain 2 2 (Q1 (cm) (kg/cm 1 (%) 1k9/cm 1 (kg/cm 1 0.00 0.0000 0.00 0.000 2.500 2.50 0.12 0.0254 0.05 0.272 2.461 2.45 0.43 0.0508 0.11 0.648 2.429 2.39 0.97 0.0762 0.15 0.984 2.436 2.35 4.63 0.1143 0.27 1.532 2.638 2.23 12.06 0.1524 0.51 2.080 3.048 1.99 18.56 0.2286 0.86 3.219 3.248 1.67 21.10 0.3048 1.12 4.359 3.187 1.38 22.72 0.3810 1.28 5.421 3.145 1.22 24.02 0.4572 1.42 6.518 3.091 1.08 24.56 0.5334 1.54 7.477 2.995 0.96 25.10 0.6096 1.63 8.574 2.925 0.87 26.62 0.7620 1.81 10.630 2.820 0.69 27.27 0.8890 1.91 12.480 2.727 0.59 28.02 1.0160 1.98 14.331 2.670 0.52 29.00 1.1481 2.04 16.130 2.638 0.46 29.43 1.2827 2.11 17.929 2.553 0.39 30.08 1.3589 2.12 18.785 2.568 0.38 31.16 1.4859 2.15 20.670 2.564 0.35 31.27 1.5240 2.16 21.184 2.547 0.34 * water content and dry density after consolidation 154 TABLE 0.16 TRIAXIAL TEST DATA Combined Sludge after Partial Decomposition CU-CDI Consolidation press. = 1.0 kg/cm2 Water content* = 115% Strain rate = 0.0036 cm/min Dry density* = 37.0 PCF 5'1. = 1.106 kg/cm2 ‘8' = 100% &3f = 0.25 kg/cmz )4f = 0.88 uf = 0.75 kg/cmz cu = 0.428 kg/cm2 cv = 7.7x10'6 cm2/sec load displacement pore axial 5‘1 5'3 pressuEe strain 2 2 (kg) (cm) (kg/cm 1 (%) (kg/cm 1 (kg/cm 1 0.00 0.0000 0.00 0.000 1.000 1.00 0.68 0.0203 0.04 0.187 1.006 0.96 2.16 0.0381 0.10 0.395 1.047 0.90 4.89 0.0635 0.19 0.715 1.140 0.81 7.51 0.1016 0.30 1.240 1.205 0.70 8.66 0.1397 0.33 1.706 1.249 0.67 9.41 0.1778 0.43 2.166 1.197 0.57 10.01 0.2159 0.46 2.626 1.203 0.54 10.71 0.2794 0.50 3.502 1.203 0.50 11.47 0.3683 0.54 4.536 1.205 0.46 11.74 0.4318 0.57 5.326 1.186 0.43 12.39 0.5842 0.62 7.208 1.162 0.38 13.31 0.7366 0.68 8.989 1.144 0.32 13.47 0.8915 0.70 10.770 1.118 0.30 13.85 0.9652 0.71 12.221 1.117 0.29 14.12 1.0693 0.72 13.370 1.112 0.28 14.66 1.2962 0.74 15.000 1.108 0.26 15.09 1.3589 0.75 16.673 1.106 0.25 15.15 1.5418 0.77 18.756 1.067 0.23 15.47 1.7018 0.77 20.552 1.066 0.23 * water content and dry density after consolidation 155 TABLE 0.17 TRIAXIAL TEST DATA Combined Sludge after Partial Decomposition CU-CDZ Consolidation press. = 1.75 kg/cm2 Water content* = 100% Strain rate = 0.0035 cm/min Dry density* = 41.8 PCF 6}” = 1.950 kg/cm?’ '5 = 100% 63,. = 0.50 kg/cmz Af = 0.86 uf - 1.25 kg/cm2 cu = 0.725 kg/cm2 cv = 6.8x10'6 cmzlsec load displacement pore axial 651 . E}: pressuEe strain 2 2 (k9) 1cm) (kg/cm1 (%1 09/ch (kg/cm 1 0.00 0.0000 0.00 0.000 1.750 1.75 4.63 0.0762 0.25 0.918 1.840 1.50 10.44 0.1143 0.43 1.382 2.082 1.32 12.71 0.1524 0.57 1.835 2.104 1.18 14.93 0.1930 0.69 2.317 2.139 1.06 16.77 0.2540 0.82 3.142 2.132 0.93 17.96 0.3302 0.94 4.085 2.085 0.81 18.18 0.3505 0.95 4.278 2.088 0.80 19.58 0.4775 1.08 5.898 2.034 0.67 20.39 0.5588 1.12 6.175 2.038 0.63 20.72 0.6350 1.16 7.636 2.006 0.59 20.99 0.7112 1.18 8.527 1.991 0.57 21.42 0.7620 1.19 9.181 2.000 0.56 22.07 0.8560 1.25 10.250 1.966 0.50 21.75 0.9271 1.25 11.112 1.931 0.50 22.07 1.1049 1.29 13.221 1.877 0.46 22.07 1.2700 1.32 15.227 1.815 0.43 22.07 1.3487 1.32 16.044 1.801 0.43 22.18 1.5240 1.35 18.242 1.742 0.40 21.96 1.6891 1.37 20.055 1.679 0.38 * water content and dry density after consolidation 156 TABLE 0.18 TRIAXIAL TEST DATA Combined Sludge after Partial Decomposition CU-C03 Consolidation press.= 2.5 kg/cm2 Strain rate = 0.0035 cm/min Water content* = 101% Dry density* = 40.7 PCF 61f = 2.046 kg/cm2 5 = 100% 07-31. = 0.39 kg/cmz A1, = 1.27 u1. = 2.11 kg/cm2 cu = 0.828 kg/cm2 2 cv = 5.8x10'6 cm [sec load displacement pore axial 5‘1 {—73 pressuEe strain (kg) 1cm (kg/cm ) (%) (kg/cm?) (kgzcm21 0.00 0.000 0.00 0.000 2.500 2.50 4.31 0.0381 0.22 0.430 2.588 2.28 8.92 0.0635 0.42 0.717 2.717 2.08 12.61 0.1016 0.61 1.144 2.786 1.89 14.99 0.1397 0.79 1.571 2.771 1.71 16.61 0.1905 0.97 2.189 2.698 1.53 18.45 0.2413 1.17 2.861 2.619 1.33 19.96 0.3175 1.34 3.778 2.541 1.16 20.29 0.3810 1.46 4.583 2.432 1.04 21.26 0.4572 1.57 5.508 2.375 0.93 22.50 0.6096 1.73 7.178 2.272 0.77 23.59 0.7620 1.83 8.998 2.214 0.67 24.78 0.9525 1.92 11.265 2.161 0.58 25.64 1.1176 2.01 12.935 2.096 0.49 26.29 1.2776 2.05 14.799 2.061 0.45 27.91 1.4605 2.11 16.962 2.057 0.39 28.24 1.5850 2.11 18.453 2.046 0.39 28.46 1.6383 2.11 19.125 2.045 0.39 28.67 1.6891 2.12 19.647 2.037 0.38 28.78 1.7272 2.12 20.169 2.032 0.38 * water content and dry density after consolidation 157 TABLE D.19 TRIAXIAL TEST DATA Combined Sludge after Partial Decomposition CU-C04 Consolidation press. = 31) kg/cm2 = 0.0036 cm/min Strain rate Water content* = 110% Dry density* = 37.0 PCF Er1f= 1.483 kg/cm2 8'= 100% EFBf = 0.58 kg/cm2 Af = 2.68 uf = 2.42 kg/cm2 cu = 0.452 kg/cm2 cv = 2.2x10'6 cm2/sec load displacement pore axial Efd Ef3 pressuEe strain 2 (kg) (cm). (kg/cm ) (%) (kg/cm?) (kg/cm.)_. 0.00 0.0000 0.00 0.000 3.000 3.00 0.24 0.0254 0.06 0.165 2.956 2.94 1.34 0.0508 0.27 0.462 2.821 2.73 3.46 0 0762 0.46 0.755 2.775 2.54 5.50 0.1016 0.63 1.014 2.742 2.37 7.88 0.1397 0.87 1.433 2.661 2.13 9.20 0.1778 1.07 1.910 2.547 1.93 10.39 0.2286 1.28 2.558 2.412 1.72 10.93 0.2794 1.46 3.185 2.264 1.54 12.06 0.4318 1.87 4.894 1.915 1.13 13.09 0.5842 2.08 6.546 1.757 0.92 13.58 0.7366 2.23 8.227 1.622 0.77 14.34 0.8890 2.31 9.965 1.573 0.69 14.77 1.0414 2.39 11.702 1.502 0.61 15.09 1.1176 2.42 12.557 1.483 0.58 15.53 1.1938 2.46 13.412 1.460 0.54 15.63 1.3462 2.50 15.121 1.408 0.50 16.28 1.4986 2.54 16.830 1.386 0.46 16.45 1.6510 2.57 18.610 1.346 0.43 16.77 1.8034 2.61 20.177 1.306 0.39 * water content and dry density after consolidation 158 TABLE 0.20 TRIAXIAL TEST DATA Combined Sludge after Partial Decomposition CU-CDS Consolidation press. = 3.0 kg/cm2 Water content* = 100% Strain rate = 0.0034 cm/min Dry density* = 39.1 PCF Erlf = 2.295 kg/cm2 8’= 100% Ei3f = 0.77 kg/cm2 Af = 1.46 uf = 2.23 kg/cm2 cu = 0.763 kg/cm2 4.3x10"6 cmzlsec 0 ll ‘_ H v—u I load displacement pore axial 5‘1 (T3 pressuEe strain 2 2 (kg) (cm) (kg/cm.) (%). (kg/cm ) (kg/cm ) 0.00 0.0000 0.00 0.000 3.000 3.00 5.71 0.0254 0.13 0.231 3.268 2.87 8.44 0.0381 0.25 0.397 3.337 2.75 13.52 0.0762 0.55 0.869 3.386 2.45 15.47 0.1143 0.82 1.377 3.245 2.18 17.64 0.1651 1.17 1.970 3.036 1.83 19.64 0.2286 1.42 2.789 2.912 1.58 20.99 0.3556 1.54 4.472 2.859 1.46 21.96 0.4318 1.76 5.419 2.690 1.24 22.50 0.5842 1.96 7.313 2.495 1.04 23.59 0.7366 2.08 9.116 2.416 0.92 24.34 0.8890 2.16 11.010 2.352 0.84 24.78 0.9652 2.18 11.971 2.342 0.82 24.99 1.0414 2.22 13.219 2.293 0.78 25.43 1.1176 2.23 14.045 2.295 0.77 25.53 1.2192 2.26 15.172 2.251 0.74 25.43 1.3030 2.31 16.299 2.175 0.69 25.75 1.3716 2.32 17.126 2.169 0.68 25.97 1.5240 2.37 18.854 2.100 0.63 25.75 1.6002 2.38 19.906 2.059 0.62 * water content and dry density after consolidation APPENDIX E mm.H u aummmm mo Logan; m.m 613m11 mum Au» mg n > .84 m.HN n xv cmucmu «_ucwu m um.H nm.~ mm.H u m¢~.om\m-.fie u .14; Se. Saw in. kuw 08. 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