METAL CYCLENG 5N MAC ROPHMTE DOMEN TED WASTEWA’ ER ‘3 LAMBS ‘E’?’ either?) ergeer of MEG GAR ESTATE {Hi ME 313 1:13 A 35.53.. TH 1973 M MSW U53 LIBRARY Michigan §tatfl Univcmty Al“; I ammuc av ‘=' "0A9 & SflNS' 800K BINDERY INC. LIBRARY RlNheae n_m"" : ABSTRACT METAL CYCLING IN MACROPHYTE DOMINATED WASTEWATER PONDS BY Douglas A. Bulthuis Sediments and aquatic vascular plants are potential sinks for contaminating elements in wastewater stabilization ponds as they are operated in Michigan. The accumulation of several heavy metals in these sinks was studied during the growing season in an existing series of stabilization ponds. Using inflow and outflow data, an approximation of the ac- crual was made for each element in bottom sediments. Bio— mass estimates of the hydrophyte communities were used to determine the quantities of metals removable from a system by harvest of a season's crOp. The ambient concentrations of chromium, copper, iron, manganese and zinc were reduced in the ponds through accumu- lation in these sinks. The ambient concentrations of cadmium, cobalt and nickel were not reduced in the ponds. Estimates were made of the relative efficiencies of removal by plant absorption and by sedimentation in aerobic ponds during the growing season. Plant absorption was more efficient than sedimentation for iron and manganese. Sedimentation was more efficient than plant absorption for chromium, copper and zinc. Sedimentation and plant absorption were equally inefficient for removal of cadmium, cobalt and nickel. METAL CYCLING IN MACROPHYTE DOMINATED WASTEWATER PONDS 33’ e A Douglas Ai Bulthuis A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Fisheries and Wildlife 1973 ACKNOWLEDGEMENTS I wish to express my sincere thanks to Dr. C. D. McNabb for serving as my major professor, for his invaluable guidance, encouragement and help through all phases of my graduate program and thesis preparation and for his interest in me and in my professional deve10pment. I wish to thank Dr. B. D. Knezek for serving on my graduate committee, for the use of laboratory facilities for metal determinations and for advice and encouragement during the development of the thesis; Dr. N. R. Kevern for serving on my graduate committee; and Dr. T. G. Bahr for substituting in my oral examination and assisting in the editing of the thesis. I wish to thank many fellow graduate students for ideas and assistance and especially John Craig, Jerry Lisiecki and David Mahan for their assistance in the field and in the laboratory in a cooperative project. I wish to express special thanks to my wife, Pam, for her moral and financial support and for her encourage- ment during all phases of my program of study. The work upon which this thesis is based was sup- ported in part by funds provided by the E.P.A. — O.W.P. Training Grant WP-264, the Michigan Agricultural Experiment ii Station at Michigan State University and the United States Department of the Interior, Office of Water Resources Research, Grant A-073-MICH, as authorized under the Water Resources Research Act of 1964. INTRODUCTION . . DESCRIPTION OF STUDY METHODS . . . RESULTS . . . DISCUSSION . . . CONCLUSIONS . . LITERATURE CITED . APPENDIX . . . TABLE OF CONTENTS SITE iii Table 1. Al. A2. A3. A4. A5. LIST OF TABLES The mean concentration (ppb) Of the non-mobile metals in the unfiltered water of the ponds in the Belding, Michigan, sewage system for the growing season of 1972. . . . Coefficients of partitioning of mobile metals in ponds of the Belding, Michigan, system. The total input to each pond for the growing season is taken as 1.00. . . . . . Coefficients of partitioning to the season- end communities and sediments in aerobic ponds in the Belding, Michigan, system. The total input to each pond for the growing season is taken as 1.00. . . . . . . . . . The mean total concentration (ppb) of selected metals in the pond water in the Belding, Michigan, sewage stabilization system for the growing season of 1972. . . . Mean concentration (ppm of dry weight) of zinc, c0pper, iron and manganese and percent ash in each species of the season-end community of submersed hydrophyte in the Belding, Michigan, sewage stabilization system. (Mean S.E.). . Mean concentration (ppm of dry weight) of chromium, nickel, cadmium and cobalt in each species of the season-end community of sub- mersed hydrOphytes in the Belding, Michigan, sewage stabilization system. (Mean S.E.). . The budgets of selected metals in the Belding, Michigan, sewage stabilization system for the growing season of 1972 in grams. . . Coefficients of partitioning of non-mobile metals in ponds of the Belding, Michigan, system. The total input to each pond for the growing season is taken as 1.00. . . . . iv Page Figure LIST OF FIGURES The system of waste stabilization ponds receiving the untreated sewage of Belding, Michigan. . . . . . . The volume of inflow, net storage, seepage, net evaporation and outflow in millions of liters of water for the stabilization pond system of Belding, Michigan, during the June-September interval of 1972. . . The submersed hydrophyte vegetation of Pond 3 in the Belding, Michigan, sewage stabilization system in September, 1972. . The submersed hydrOphyte vegetation of Pond 4 in the Belding, Michigan, sewage stabilization system in September, 1972. . The submersed hydrophyte vegetation of Pond 5 in the Belding, Michigan, sewage stabilization system in September, 1972. . The copper budget of ponds in the Belding, Michigan, sewage stabilization system for the growing season of 1972 in grams. . . Page INTRODUCTION Municipal waste treatment schemes for the Great Lakes region are currently incorporating land disposal of effluent as a means of locally trapping eutrOphying elements (Anon., 1970; Anon., 1971; Bahr, 1972). Stabilization ponds or storage ponds are an ordinary part of these designs. Presumably, knowledgeable manipulation of the communities of the ponds can play a role in Optimizing treatment in the system as a whole. The mechanisms controlling BOD, coliform, nitrogen and phosphorus dynamics in such ponds have received considerable attention in the literature (Fitzgerald and Rolich, 1958; Towne, Bartsch, and Davis, 1957). Evaluation of the long term feasibility of these systems requires a consideration of the mechanisms that control the dynamics of the other materials in the waste, including metals. Many stabilization pond systems in Michigan are designed so that anaerobic, facultative and aerobic cells (of. King, 1967) exist in a series during the summer irri- gation season. Regarding plant communities, facultative cells are dominated by assemblages of chlorophycean algae of the types described by Mackenthun and McNabb (1959). Aerobic cells are dominated by submersed macrophytes. In addition to being responsible for biological aeration, these plant communities have an influence on pH and redox potentials (Wium-Andersen and Andersen, 1972). Hence, they play a key role in pond function by exerting a control on the solubility of a variety of compounds and complexes. They also represent a sink for eutrOphying elements that could be removed to take these from the site (McNabb and Tierney, 1972). Economic use of such aquatic plants have been con- sidered by Little (1968), Bagnall, Casselmann, Kesterson, Easley and Hellwig (1971) and others. The following hypotheses regarding the dynamics of cadmium, chromium, cobalt, copper, iron, manganese, nickel and zinc are addressed: 1) the concentration of each of these elements is reduced in the water as it moves through facul- tative and aerobic cells in a series of stabi- lization ponds during the growing season. 2) during the growing season natural aquatic macro- phyte communities accumulate a larger fraction of each incoming element than do the sediments of aerobic stabilization ponds. DESCRIPTION OF STUDY SITE The city of Belding, located in the southwest quad- rant of the lower peninsula of Michigan, has a stabilization pond system consisting of a series of five cells. The ponds cover about 23 hectares, have a maximum depth of 2 meters and serve a population of about 5000. Untreated waste from the primarily residential community enters Pond l and flows by gravity through Ponds 2, 3, 4 and 5 (Figure 1). There are three types of ponds within the series: anaerobic, faculta- tive and aerobic. Pond 1, an anaerobic cell, is characterized by a lack of oxygen, apparent black colored water, and pro- duction of gas that continually breaks the surface. Pond 2, a facultative cell, is characterized by a dense phytoplackton bloom throughout the summer, high dissolved oxygen at the surface, decreasing dissolved oxygen going deeper in the water column and black, gas producing anaerobic sediments. Ponds 4 and 5 are aerobic, are dominated by submersed macrophytes, have dissolved oxygen will mixed throughout the water column and have sediments that are light colored and aerobic at the mud-water interface. Pond 3 fluctuates between the faculta- tive and aerobic state. Light intensity at the bottom of Ponds 4 and Shad a mean seasonal value of about 25% of the surface light and the light intensity at 2 meters corresponded to the light intensity at about 0.3 meter in the facultative pond. mocom newumufiflnmum mummz mo Emummm one .H Gunman ...3“..»M.un.u.. o cmmfl£0flz 5 val-HUme . unmwwmwmwvnn mo mmm3mm omummuucs on» mcfi>flwomn H .aa.u-..m :35... a..< 32...... .u: —.o Lawn” .... ob auuazm ..... 2.2.2; .2. —.o n 9.3.— »: a he aaaaa ccccc ..... 00000 ..... ..... =o_.nu._._ METHODS Flow between the ponds was measured every ten days in the growing season with a Gurley current meter lowered into submerged conduits of known diameter through a stand— pipe on the dike between the ponds. Water samples were collected in the conduits and in the ponds and concentrated by freeze drying. In early September transects of the plant communities were examined to determine the percent cover of species comprising the terminal crOp of the season. Quan- titative samples were taken within stands of each species for biomass estimates and metal determinations. Observations of growth early in the season indicated that this crOp de- veloped in circa 80 days. Whole plants were collected, washed in pond water, placed in polyethelene bags, dried in a forced draft oven at 80°C and weighed. The plants were crushed by hand in the polyethelene bags. Five grams of plant tissue were wet ashed with 200 m1 of a 20 to l HNO3 and HClO4 acid mixture in a Bethge distillation apparatus. The freeze dried resi- dues of water samples were wet ashed with 100 ml of a 20 and HClO to 1 HNO 4 acid mixture in the same apparatus. 3 Metal determinations of the plant and water concentrates were made by atomic absorption spectr0photometry on a Perkin Elmer model 303. Dry weight estimates are based on a mean of 12 samples; plant metal concentrations on a mean of 4 to 6 samples. RESULTS Measurements of the volume of flow between the ponds were used to obtain a mean that was taken as the daily input or output of each pond in the system for the 80 day growing season. A water budget constructed from these data is shown in Figure 2. During the growing season 157 million liters entered the system and 2 million liters were taken from Pond 5 for spray irrigation on adjacent land. The water level in the ponds was raised 0.3 meter so that part of the water and elements that entered each pond were accounted for by this storage. The evaporation data represent a net exchange with the atmosphere as measured by a rain gauge and evaporating dish located at the site. Percolation out of the ponds was calculated by subtraction. Pond 5 in this system was de- signed to act as a seepage pond and had a considerable flow through the bottom. The last three ponds in this system were dominated by submersed hydrophytes. The community in Pond 3 consisted primarily of Ceratophyllum demersum L. (coontail). Late in the season the c. demersum floated to the surface and pro- vided an area sheltered from wave action upon which Lemna minor L. (duckweed) expanded to completely cover the C. demersum mat. The aspect of this vegetation is shown in Figure 3. Figures 4 and 5 show the nature of the hydr0phyte 7 .mhma mo Hm>umucH nonfimummmumcsb onu mcfluso .cmmwnoflz .mcwoamm mo Emumhm ocom coHDMNHHHnmum map How Hmum3 mo mumufla mo mCOAHHHE ca 30Hmuso was coflumuomm>m umc .mmmmmmm .mmmnoum um: .30Hmcfi mo mEDHo> was .m musmflm . .Nnma .HmoEmummm CH Emummm cofluMNHHflnmum mmm3mm .cwmflzOAE .mcfloamm may ca m ocom mo coflumummm> mumzmonohn ommuwfinsm was .m madman Mig/ L. Emmi? .3..- -, I 2.3:: 5.3.5:... 31.53222: 5.3.5:... 53......- 5:2...323 ._‘ 9 «\W .2 a: .6" 3&3: 3......— 3. 2; 3.3:: 53:53.". a :58 25.33 s 2.... .55 i \ \ \ . 2.x: 2*. ~52..- \ 10 man— «— F6 eo— au— new .=.a .a .g\.: .thH .mmnfimummm CH Emumwm cofiumeHHnmum mmmzwm .mcfioamm may a“ w ocom mo coflumummm> muwcmouoms ommuwansm one .cmmflaoflz .v musmwm Ex? .33223’ =e...asa.om A 32%... E I 2.3:: =o...esa.e 4r..on__i.. a.osnoaa_o ~.o A~.vhv a_~ _.o Am.n_v No «.3. 2.": an o.¢ Aa.nmv va— sén 3.98 .2 . =._..ou .a..o...wo 2:... .5 .5 :5». ~52... hflfd a.ua._. .o_=u_... noon sozagm m=m9:o.. E=»_.Eou. E=u_.soa . s. i .oe.s ‘ 52.23.23 ‘ «use; .. 2 fl htaufluoxuuvzl. IT... . . . . Q A....:”’~. Ammmwi. ‘00.:‘ d0 0‘ . scam .mnma .Hmnfimvmmm ca Emummm soflumeHwnmum mmmsmm .GMGASOAZ .mcfloamm may CH m coon mo cowumummmb mum£m0HOM£ ommumensm was .m musmfim A 3:: #3." ”2......“ Sci-=8 8.3.: out... ‘ 5.3.2.. .. fl I on. no on... o v .. n :3... a . .g‘ \ I yé-a . u¢.a le.ms :. a: 9.: 2.5 .3 2:: .u 2 3 a: 3.3.: J 2 ~._ 3.»: 3 3.2.2: 2:333... .. z 2 3.5 : 3.3.3.. .._ z E 9.5 2. 2:252. .._ 2.8. .228 35 .33 .o .3... .5 to 2:: 3* ~52.» m E3; .mnma .HmnEmummm ca Emumxm coflumNflHflnmum mmmzom .cnmwsowz .mcficawm may CH m ucom mo :oHumummm> mumnmouomn vomumfinnm was .m musmwm ...... ... .wa rm." ....o . Inn-.....a .. . .u 3.3... ...-3‘ ......:..:.. .. , fl . . .... a. on... o v _ u :3... . . ...! \.\n%a {I 1 I! ? }wman..o.1. cow-p.32: _ » cut-a . o.. . ... v ...... .32....- . .. .... ... a ; . 3% n. :0 ... .... .. 1.38...» flu... ...: 2.5 .3 22:. ... swag.........”...._..,.._.,,...........”... .. . . .... «é u: 8.3... .. ... . > > > a 2 ~.. 3.2. 3 «...-u... D a > 223.3..- d 2 _.~ 3&3 ca 328:..- ... : ... 3.... 2. 3.2.2:. .. ago; u....oo fipoa.a.m. .. ...... ......a ugxux ...» «axl- 3 age. 11 3. a; m— N— .2 .. .3.., .. ..\.g . .Nnma .HmnEmummm 2H EmumMm :oflumNfiHHnmum mmmzmm .cnmflsowz mcflwawm map ad m econ mo coflumummm> wumnmouomn cumumensm may .m muzmam » ..u-._ I 33.3..” 2.3.0:... ...-:39... ..— 3...... 3.3... 3|... ‘ fl . .333... ......l....‘ \v. y I ‘l v ...... 3...... ...: 2.5 .2 22:. ... 2 .2 3.3... .. ~.. 2.2. .. 2.2:... ......g.... .. ..N 2.5 : ......3... .. ... 2.3 ... ”...-...: .. .228 35 .33 ...... ..3 .5 :1. ~53. m 9...... 12 communities in Ponds 4 and 5 in early September when tran- sects of the plant communities were made. Combining the volumes of flow (Figure 2) with the trace metal concentrations in the water and plants, budgets were constructed showing the amount of metal accumulated in the various components of the plant dominated ponds over the growing season. The biomass estimates for the macrOphyte communities, given in Figures 3, 4 and 5, were used to ob- tain the total amount of each metal held in the plant community. The copper budget is presented in Figure 6. It re- veals a stepwise decrease in copper load as the water moves through the ponds. Pond 2 was most effective and Ponds 3 and 4 less so in reducing the copper load in the water. This reduction was reflected in the seasonal mean of 21 ppb total c0pper entering Pond 2 and less than 2 ppb in Pond 5 (Cf. Table 1). An entry has been made in Figure 6 to account for the amount of c0pper contained in the volume of water stored in each pond over the growing season. This volume is ordi- narily discharged to an adjacent stream in September. The Belding system is similarly drawn down in early April to accomodate the growing season storage. Note from Figure 6 that 175 grams of copper either moved with seepage water through the bottom of Pond 5 or was adsorbed by the soil through which the water moved. Similar budgets were constructed for the other metals studied. The elements were divisible into two groups: those 13 .mEmHm ca mnaa mo c0mmmm mcflzoum may HON Emumwm coflumNHHHnmum mmmzmm .cmmflcoflz .mcwcawm map cH mocom no #00059 Hommoo one .w wusmflm m :29; 14 that decreased through the system (non-mobile) and those that remained relatively constant through the system (mobile). Those that decreased, in addition to COpper, were zinc, iron, chromium and manganese. The concentrations of these metals in the different ponds are presented in Table 1. As the water flowed through the system, a large por- tion (66%) of the zinc moved to the sediments in Pond 2; the zinc concentration remained the same in Pond 3, and was re- duced in Pond 4 where 37% of the pond input moved to the sediments. The plant communities in cells 3, 4 and 5 accu- mulated 5—6% of each pond's zinc input. In Pond 5, where the concentration was the same as in Pond 3, 70% of the in- put either moved with the seepage water or was adsorbed by the soil through which the water moved. Chromium was reduced regularly in each pond. Forty percent of the Pond 2 input went to the sediments, while 20% of the input of Ponds 3 and 4 went to their sediments. Very small fractions (l-2%) of the input chromium went to the plants of Ponds 3, 4 and 5. Eighty five percent of Pond 5's input moved with the seepage water or was immobilized in the bottom sediments. Iron and manganese were reduced considerably in Pond 2 where 75% and 50% respectively were trapped in the sedi- ments. In Pond 3, (11 kg Fe and 4.3 kg Mn entering) the plants accumulated large amounts of the metals (.96 kg Fe and 8.2 kg Mn) while the sediments released even larger a- mounts (l.8 kg Fe and 9.8 kg Mn). This resulted in increased 15 Table 1. Mean concentration (ppb) of the non-mobile metals in the unfiltered water of the Belding, Michigan, sewage stabilization system for the growing season of 1972. Zinc Copper Chromium Iron Manganese Pond 1 . Effluent 70 21. 8.5 340 73 Pond 2 Effluent 25 6.8 5.2 96 38 Pond 3 Effluent 25 3.3 4.3 110 59 Pond 4 Effluent 15 2.9 3.5 100 30 Pond 5 25 -- -- 67 14 16 concentrations of iron and manganese in the Pond 3 effluent. There was a net movement of iron and manganese out of Pond 4 sediments (1.8 kg Fe and 6.3 kg Mn), but large quantities taken up by the plants (2.8 kg Fe and 9.1 kg Mn) helped to lower the water concentrations. In Pond 5 (8.1 kg Fe and 2.3 kg Mn entering) 31% of the input iron was trapped in the plants and 60% moved with the seepage water or was immobi- lized in the bottom sediments.‘ The Pond 5 plant community accumulated 2.5 kg of manganese indicating a net movement of manganese out of the sediments (.36 kg). In contrast to the non-mobile metals which had a tendency to become trapped in some portion of the system, several of the metals were not reduced or reduced very little as they moved through the ponds. This is shown in Table 2 to be the case for cadmium, cobalt and nickel. The coef— ficients of partitioning shown in Table 2 are fractions of the growing season input that accumulated in each component at the end of the growing season. The low coefficients to plant uptake and sedimentation indicate the low amounts be- ing trapped in the ponds. Throughout the system total nickel averaged 13 ppb, cobalt 15 ppb and cadmium 2.1 ppb. At the end of the growing season, a portion of the metals which entered each pond during the summer was trapped in the plant community. The tendency to concentrate these elements is shown in the cOmpilation of Chapman, Fisher and Pratt (1968). As the plants age and decay, the metals that had been in them moves to the sediments or is released to 17 Table 2. Coefficients of partitioning of mobile metals in ponds of the Belding, Michigan, system. The total input to each pond for the growing season is taken as 1.00. Pond Water Plant Metal Pond Sediment Stored Uptake Output Nickel 2 .28 .12 .60 3 .02 .14 .02 .82 4 .04 .10 - .02 .84 5 .78* .17 .01 .04* Cadmium 2 . .03 .17 .80 3 -.01 .17 01 .83 4 .04 .ll .01 .84 5 .84* ' .12 .005 .03* Cobalt 2 .02 .17 .81 3 .00 .16 .01 .83 4 .03 .10 .01 .86 5 .85* .12 .005 .03* *For Pond 5, sediment value is quantity carried into bottom by high-rate seepage flow; volume of output very low. 18 the water (cf. Cowgill, 1968; Kimball, 1973). Harvest of the plant community at maximum biomass could remove this fraction from the system. Using the biomass of each species in the pond with the concentration in each species and the amount of metal entering each pond, the percentage of the total metal entering the ponds over the growing season which could be harvested in the plant communities was estimated. The coefficients of partitioning to the plants in Ponds 3 and 4, given in Table 3, indicate the percentage of the in— put that could be harvested. Harvest of the plant crops would yield between 1 and 2% of the cadmium, chromium, co- balt and nickel entering each pond during the growing sea- son and a slightly higher percentage of the c0pper and zinc (4-7%). Sediments were equally ineffective in accumulating the cadmium, cobalt and nickel. However, sedimentation re- moved substantially greater percentages of c0pper, chromium and zinc depending on the particular pond (cf. Table 3: COpper-Pond 3, zinc-Pond 4, chromium-Ponds 3 and 4). The plants accumulated iron and especially manganese. In con- trast there was a net movement of iron and manganese out of the sediments during the growing season as indicated by the negative values in Table 3. 19 Table 3. Coefficients of partitioning to the season-end communities and sediments in aerobic ponds in the Belding, Michigan, system. The total input to each pond for the growing season is taken as 1.0. Pond Sink Ni Cd Co Cr Cu Zn Fe Mn 3 Plants .02 .01 .01 .01 .04 .06 .09 1.90 3 Sediments .02 -.01 0.00 .18 .49 .02 —.16 -2.28 4 Plants .02 .01 .01 .02 .07 .05 .28 1.69 4 Sediments .04 .04 .03 .20 .09 .37 -.18 -l.l7 DISCUSSION The hypotheses to which this study was addressed have been rejected on the basis of the data that were obtained. Regarding the first of these (that the metal concentrations would be reduced), the concentration of certain metals was reduced as the wastewater moved through the series of ponds at Belding, Michigan. COpper, zinc, chromium, iron and man- ganese were all immobilized such that mean seasonal concen- trations were reduced from the higher values observed at the input to Pond 2 to the lower values observed in Pond 5 (Table 1). However, contrary to the first hypothesis, cad- mium, cobalt and nickel were not immobilized in this system. This mobility might be expected of nickel and cobalt because of their relatively soluble salts (Kopp and Kroner, 1970), but cadmium, which in this series was mobile, is usually re- ported as having chemistry similar to zinc (Hem, 1972; Leeper, 1972), which in this series was immobilized. Apparently these mobile metals are not being precipitated with iron or man- ganese oxides, nor being removed through adsorption on set- tling organic matter. Their mobility may be due to chelation by soluble organics. The literature concerning the movement of metals in aquatic systems with concentrations of suspended and soluble 20 21 organics and inorganic compounds of the quality, quantity and ratios encountered in stabilization pond systems is scant. For rivers and other bodies of natural water Jenne (1968) proposes that precipitation and dissolution of hydrous oxides of iron and manganese are often the control— ling mechansim of the concentration of many of the heavy metals. Adsorption to suspended organics which slowly set— tle is another potential controlling mechanism. If a single driving mechanism were controlling the concentration of all of the heavy metals in stabilization ponds, manipulation of the ponds for removal of all the heavy metals could cen- ter on that mechanism. When several mechanisms are opera- tive, manipulation of the system to optimize immobilization of all the heavy metals becomes complex. The reduction of the metals that were immobilized was not uniform for all metals; each metal exhibited unique characteristics in its budget. As an example, in Pond 3, 49% of the input copper was deposited in the sediments and only 2% of the input zinc. There was the reverse relationship in Pond 4 where 9% of the input copper and 37% of the input zinc was deposited in the sediments. This dissimilarity in response indicates more than one mechanism controlling the reduction of these metals. COpper may be reduced by adsorption to suspended organics in Pond 3 with primarily chelated copper entering Pond 4. If the c0pper were chelated with soluble organics very little of the copper entering Pond 4 would be expected to settle to the sediments. Zinc is not as tightly bound 22 to organic material as c0pper (Krauskopf, 1972) which might explain zinc's mobility in Pond 3. The plant community in Pond 4 may be raising the pH higher than in Pond 3 and pre- cipitating zinc compounds which have a minimum solubility around a pH of 9.5. The mechanisms that are important in trapping metals in a facultative pond may be different than the important mechanisms in the aerobic ponds. In Pond 2, a large portion of the metals that entered were immobilized in the sediments. This movement to the sediments may be effected by the set- tling of the organic and suspended solids that enter the pond. Copper, chromium and zinc have all been reported to be adsorbed to these materials (Krauskopf, 1972; Leeper, 1972; Hem, 1972). The photosynthetic activity of the algae main- tained a saturation of dissolved oxygen and pH in the range of 8-9 in the upper layers of the pond. Under these condi- tions most metal ions form precipitates or may be incorporated into or on hydrous oxides of iron and manganese (Jenne, 1968). In the lower layers of the facultative cell sulfides of iron, c0pper and zinc may be forming (Cowgill, 1968; Hem, 1972). The aerobic cells were dominated by submersed macro- phytes that tend to regulate the pond chemistry by contri- buting to a high dissolved oxygen and pH through all depths. Generally the same mechanisms of precipitation, sorption to hydrous oxides and settling solids would be operative in these cells as in the upper layers of the facultative cell. Sulfide precipitation would not be important as the bottom 23 of the ponds was covered with an aerobic layer of sediments. The aerobic ponds had the additional mechanism of cation up- take by the submersed macrophytes. The iron and manganese budgets seem anamolous. In anaerobic, reducing environments, iron and manganese are usually soluble and in aerobic, oxidizing environments they tend to precipitate as oxides. However, 75% and 50% of the input iron and manganese respectively settle to the sediments in the facultative Pond 2 wich is partly anaerobic and there is a net movement out of the sediments in the aerobic ponds. The high sedimentation rates in Pond 2 may be caused by a combination of settling adsorbed and suspended metals and the formation of iron sulfide which is highly insoluble. In Ponds 3 and 4 the net seasonal movement of iron and manganese out of the sediments may be explained by their uptake by the plants from the sediments of the pond. Regarding the second hypothesis to which this study was addressed, Table 3 indicates that plants and sediments accumulate similar fractions of the input cadmium, cobalt and nickel. Neither the plants nor the sediments were ef- fective in reducing the ambient concentration of these ele- ments. The plants accumulated smaller fractions of the in- put chromium, copper and zinc than did the sediments (Table 3). The plants accumulated larger fractions of iron and manganese than did the sediments since there was a net move- ment of these two elements out of the sediments. The metal concentrations of the plant tissues are similar to the few 24 values reported in the literature for aquatic vascular plants. However, comparison of tissue concentrations between plant communities or species sampled only once during the growing season can be misleading and not representative of the sea- sonal means (cf. Tierney, 1972). The terminal crop of the season has been considered as the harvestable unit in this study. A harvesting srat— egy that includes prOper timing to acheive effects that op- timize treatment in the system as a whole, presently escapes definition for lack of integrated information concerning the combined goals at the aquatic and land sites. The very low coefficients of partitioning to aquatic plants given in Table 3 suggest that harvesting of natural pOpulations at the end of the growing season to remove metals would be im— practical. The sampled crop, however, is not necessarily the maximum that could be obtained. On the other hand, ma- nipulation of the plant community to obtain desireable levels of dissolved oxygen, pH and redox potentials may be of con- siderable importance. CONCLUSIONS The following two hypotheses regarding the dynamics of cadmium, chromium, cobalt, copper, iron, manganese, nickel and zinc were addressed: 1) the concentration of each of these elements is reduced in the water as it moves through facul- tative and aerobic cells in a series of stabili- zation ponds during the growing season. 2) during the growing season natural aquatic macro- phyte communities accumulate a larger fraction of each incoming element than do the sediments of aerobic stabilization ponds. Both hypotheses have been rejected on the basis of the data that were obtained. Regarding the first hypothesis, the Belding sewage stabilization system reduced the ambient concentrations of chromium, copper, iron, manganese and zinc during the growing season. Ambient concentrations of cadmium, cobalt and nickel were not reduced in these ponds. Regarding the second hypothesis, plant absorption was more efficient than sedimentation for removal of iron and manganese in aer- obic ponds: sedimentation was more efficient for removal of chromium, c0pper and zinc. Plants and sediments were equally inefficient in trapping cadmium, cobalt and nickel. 25 LITERATURE CITED LITERATURE CITED Anon. 1970. Muskegon County Michigan Wastewater Management. Bauer Engineering, Inc., Chicago 60606. 228p. Anon. 1971. Recycling sewage biologically. Environ. Sci. & Tech. 1: 112—113. Bagnall, L. 0., T. W. Casselmann, J. W. Kesterson, J. F. Easley and H. E. Hellwig. 1971. Aquatic forage processing in Florida. Amer. Soc. Agr. Eng. Paper No. 71-536, St. Joseph, Mich. 49085. 41p. Bahr, T. G. 1972. Ecological assessments for wastewater management in southeastern Michigan. Tech. Rep. No. 29, Inst. wat. Res., Mich. State Univ., East Lansing 48823. 281p. Chapman, W. H., H. L. Fisher and M. W. Pratt. 1968. Con- centration factors of chemical elements in edible aquatic organisms. Lawrence Radiation Laboratory, Univ. of Calif., Livermore. 50p. Cowgill, U. M. 1968. A comparative study in eutrophication. In: Developments in Applied Spectroscopy. V01. 6. W. K. Baer, A. F. Perkins and E. L. Grove (Eds.), Plenum Press, New York. pp. 299-231. Fitzgerald, G. P. and G. A. Rolich. 1958. An evaluation of stabilization pond literature. Sewage and Ind. wastes 30: 1213-1224. Hem, J. D. 1972. Chemistry and occurence of cadmium and zinc in surface and ground waters. water Resources Research 8: 661-679. Jenne, E. A. 1968. Controls on Mn, Fe, Co, Ni, Cu and Zn concentrations in soils and water: The significant role of hydrous Mn and Fe oxides. In: Trace In- organics in water, Advan. Chem. Ser. Vol. 73. Amer. Chem. Soc., washington, D. C. pp. 337-387. Kimball, K. D. 1973. Seasonal fluctuations of ionic c0pper in Knights Pond, Massachusetts. Limnol. Oceanogr. 18: 169-172. 26 27 King, D. L. 1967. Basic studies of controlled facultative lagoons. In: Advances Toward Understanding Lagoon Behavior, Proceedings of the Third Annual Sanitary Engineering Conf., Univ. of Missouri, Columbia. pp. 88-110. KOpp, J. F. and R. C. Kroner. 1970. Trace Metals in Waters of the United States (Oct. 1, 1962 to Sept. 30, 1967). U. S. Dept. of the Interior, Fed. Water Poll. Contr. Admin., Washington, D. C. 32p. Krauskopf, K. B. 1972. Geochemistry of micronutrients. In: Micronutrients in Agriculture, J. J. Mortvedt, P. M. Giordano, and W. L. Lindsay, (Eds.), Soil Sci. Soc. Amer., Madison, Wis. pp. 7-40. Leeper, G. W. 1972. Reactions of Heavy Metals with Soils with Special Regard to their Applications in Sewage Wastes. Prepared for Dept. of the Army, Corps of Engineers under contract No. DACW 73-73-C-0026. 67p. Little, E. C. S. (Ed.). 1968. Handbook of Utilization of *Aquatic Plants. FAO, Rome. 123p. Mackenthun, K. M., and C. D. McNabb. 1959. Sewage stabili- zation ponds in Wisconsin. Comm. Wat. Poll. Bull. No. WP 105. Madison. 52p. McNabb, C. D., Jr. and D. P. Tierney. 1972. Growth and mineral accumulation of submersed vascular hydro- phytes in pleioeutrophic environs. Nat. Tech. Inform. Ser. PB-211 609, USDC, Springfield, Va. 22151. 31p. Tierney, D. P. 1972. Some aspects of the ecology of natu— rally occuring populations of submerged vascular hydrophytes in municipal wastewater lagoons. Part II. Trace element accumulation. Ph.D. Thesis, Mich. State Univ., East Lansing 48823. pp. 55-84. Towne, W. W., A. F. Bartsch, and W. H. Davis. 1957. Raw sewage stabilization ponds in the Dakotas. Sewage and Ind. wastes 29: 377-396. Wium—Andersen, S. and J. M. Andersen. 1972. The influence of vegetation on the redox profile of the sediment of Grane Langs¢, a Danish Lobelia lake. Limnol. Oceanogr. 17: 948-952. APPENDIX 28 Table A1. The mean total concentration (ppb) of selected metals in the pond water in the Belding, Michigan, sewage stabilization system for the growing season of 1972. Pond Zinc Nickel Cadmium Cobalt Iron Manganese 2 26 13 2.1 15 46 28 3 14 12 ’ 2.2 13 100 28 5 25 19 2.5 12 67 14 29 Table A2. Mean concentration (ppm of dry weight) of zinc, copper, iron and manganese and percent ash in each species of the season-end community of submersed hydrophytes in the Belding, Michigan, sewage stabilization system. (Mean i'S.E.). Percent Pond Species Ash Zn Cu Fe Mn 3 C. demersum 19.0 42 4.9 270 2400 :0.89 :4.6 :1.4 :46 :240 3 Lemna minor 19.9 37 8.8 140 1100 :1.44 :2.7 :0.93 :15 :140 4 C. demersum 19.5 32 5.1 710 2700 :4.10 :3.4 :0.77 :85 :520 4 Lemna minor 21.6 38 4.0 160 570 :0.90 :3.0 :0.36 :26 :86 4 Lemna trisulca 26.4 48 8.2 760 3800 :1.58 :6.4 +1.65 :186 :580 4 P. foliosus 11.7 23 5.1 540 830 (shallow) :0.52 :l.9 +1.42 :152 :65 4 P. foliosus 20.9 33 6.9 940 1600 (deep) :3.46 :4.7 :0.7 :225 :170 4 Cladophora 13.9 43 11.0 3800 400 fracta :0.66 :4.0 :1.33 :200 :34 5 C. demersum 18.2 34 2.7 240 3700 :1.59 :2.8 +0.19 :32 :870 5 Lemma minor 17.7 30 6.0 160 1500 :0.72 :1.2 +0.88 :12 :70 5 Lemna trisulca 20.8 50 4.0 440 5400 :0.74 :3.4 +0.43 :86 :550 5 P. pectinatus 14.4 31 4.3 1100 1100 :0.90 :3.3 +0.94 :500 :110 5 P. berchtoldi 15.3 32 4.6 3600 2100 (rooted) :2.45 :2.7 :0.84 :850 :240 5 P. berchtoldi 13.0 32 4.6 240 1700 (mat) :0.62 :l.4 :0.78 :29 :190 5 Cladophora 15.1 40 10.0 1300 1300 fracta :2.09 :2.5 :l.06 :120 :60 30 Table A3. Mean concentration (ppm of dry weight) of chromium, nickel, cadmium and cobalt in each species of the season-end community of submersed hydrophytes in the Belding, Michigan, sewage stabilization system. (Mean 18.E.). Pond Species Cr Ni Cd Co 3 C. demersum 0.8 7.9 0.58 3.9 :0.06 +0.20 :0.035 :0.24 3 Lemna minor 1.0 6.6 0.74 4.7 :0.06 :0.36 :0.086 :0.38 4 C. demersum 2.5 6.2 0.63 5.0 10.70 +0.93 :0.040 :0.27 4 Lemna minor 1.0 3.4 0.62 4.9 10.13 +0.44 10.91 10.68 4 Lemma trisulca 1.4 7.6 1.06 7.0 10.24 10.94 10.030 10.09 P. foliosus 4 1.9 5.6 0.63 6.5 ‘8ha11°w’ 10.50 11.19 10.097 10.72 4 P' 101322.: 2.5 6.2 0.69 6.4 P 10.17 10.66 10.040 10.23 4 Clad°Ph°ga t 2.0 5.9 0.42 4.4 ’ac a 10.22 10.90 10.074 10.77 5 C. demersum 0.7 4.8 0.63 4.0 10.04 10.50 10.049 10.22 5 Lemna minor 0.7 4.4 0.60 3.6 10.23 10.47 10.044 10.32 S Lemna trisulca 1.0 6.1 0.88 4.6 :0.12 :0.20 :0.120 :0.35 5 P. pectinatus 1.0 4.3 0.60 3.5 10.15 10.51 10.084 10.34 5 P. berchtoldi 1.3 5.0 0.57 4.2 (rooted) 10.16 10.27 10.039 10.48 5 P. berchtoldi - 1.0 5.6 0.84 4.2 (mat) 10.06 10.22 10.085 10.22 5 Cladophora 1.7 6.6 0.47 3.0 fracta :0.07 :0.26 :0.067 :0.31 31 Table A4. The budgets of selected metals in the Belding, Michigan, sewage stabilization system for the growing season of 1972 in grams. Water Pond Plant Metal Pond. Input Stored Sediment Uptake Output Zinc 2 9800 560 6440 2800 3 2800 260 60 180 2300 4 2300 140 840 120 1200 5 1200 220 850* 75 50* Copper 2 2900 160 1980 760 3 760 60 370 30 300 4 300 26 27 22 225 5 225 25 175* 20 5* Iron 2 48000 1100 36000 11000 3 11000 1800 ~1800 960 10000 4 10000 940 -1800 2800 8100 5 8100 600 4900* 2500 130* Manganese 2 10200 660 5200 4300 3 4300 520 -9800 8200 5400 4 5400 270 -6300 9100 2300 5 2300 130 -360* 2500 28* * For Pond 5, sediment value is quantity carried into the bottom by high-rate seepage flow; volume of output was very low. 32 Table A4. (continued) Water Pond Plant Metal Pond Input Stored Sediment Uptake Output Chromium 2 1200 120 500 580 3 580 80 106 4 390 4 390 30 80 10 270 5 270 30 230* 3 7* Nickel 2 2500 310 690 1500 3 1500 240 27 33 1200 4 1200 120 46 24 1010 5 1010 170 790* 12 40* Cobalt 2 2100 350 50 1700 3 1700 280 0 20 1400 4 1400 140 40 20 1200 5 1200 140 1020* 6 30* Cadmium 2 290 50 10 230 3 230 40 -3 3 190 4 190 20 8 2 160 5 160 20 135* 4* * For Pond 5, sediment value is quantity carried into the bottom by high-rate seepage flow; volume of output was very low. 33 Table A5. Coefficients of partitioning of non-mobile metals in ponds of the Belding, Michigan, system. The total input to each pond for the growing season is taken as 1.00. Pond Water Plant Metal Pond Sediment Stored Uptake Output Zinc 2 .66 .06 .28 3 .02 .09 .06 .83 4 .37 .06 .05 .52 .1 5 .71* .18 .06 .04* E ' Copper 2 .68 .06 .26 i 3 .49 .03 .04 .39 f*i 4 .09 .09 .07 .75 | 5 .78* .11 .09 .02* Chromium 2 .42 .10 .48 3 .18 .14 .01 .67 4 .20 .08 .02 .70 5 .85* .11 .01 .03* Iron 2 .75 .02 .23 3 -.16 .16 .09 .91 4 -.18 .09 .28 .81 5 .60* .07 .31 .02* Manganese 2 .51 .06 .42 3 -2.28 .12 1.90 1.26 4 -1.17 .05 1.69 .43 5 -.16* .06 1.09 .01* * For Pond 5, sediment value is quantity carried into bottom by high-rate seepage flow; volume of output very low. "WRIT/@1711 MIT” 11’ Iflifljfiil‘ljflflfi 11711111111“