DESIGN OF AN ADDITION TO THE EAST LANSING, MICHIGAN SEWAGE TREATMENT PLANT Thai. for GB. Dam of B. 3. MICHIGAR QTATE COLLEGE Walter A. Mischley l 947 (1., / gupmgmm' , WERWKL m BACK OF BOOK , Deeign of In Addition to the East Lansing, Michigan Sewage Treatment Plant. A Thesis Submitted to The Faculty of MICHIGAN BILTE COLLEGE of .AGRICULTURE‘IND APPLIED SCIENCE by Welter A. giggglcy Candidate for the Degree of Bachelor of Science Mardh, 1947. 1+1 2:515 c! 3/5 //L'/7 G141 LOXFONLBDGHEFT The author wishes to express hie appreciation for the help given him by Professor 1. R. Theroux, Instructor George G. Weetfsll snd _ John I. Patriarche, Superintendent Public Works, met Lansing. Michigsn. TABLE OF CONTENTS Present Sewer System PRESENT SEWAGE TREATMENT PLANT General Description Detailed Description Treatment Accomplished Chemical Analysis of influent and effluent THE PRELIMINARY SURVEY Red Cedar River Average Monthly Discharge Time of Indicated Flows Population Study of East Lansing Population Study of'Michigan State College Population Graph, East Lansing Population Graph,‘Michigan State College THE PLANT DESIGN General Data Primary Settling Tanks Aeration Tanks Final Settling Tanks Sludge Digestion Tanks Gas Storage Tanks Sewage Pumps Sludge Pumps Chlorination.Units Sludge Beds 10 11 15 14 15 16 16 17 18 l9 l9 19 20 20 2O DESIGN OF PRIMARY TANKS Design of Walls Design of Base Slab Sludge Storage Space Inlet Channel Outlet Channel Scum Trough ESTIMATE OF PLANT COST 21 25 28 28 29 50 51 PRESENT SEWER SISTER East Lansing is served with a combined sewer system which delivers the sewage to an interoepter near the Red Cedar River. The sewage from Michigan State College also enters the inter- cepter. Overflow boxes are provided so that excess eater run- off during storms may be diverted directly to the river. There are many leaks in the present system which causes an increased amount of sewage to be handled at the plant. Inverted siphons are used to carry sewage across the river. The siphons and overflow boxes are all in good condition at the present time. The.intercepter terminates as'a 53-inch concrete sewer at the sewage treatment plant on the South bank of the Red Cedar 1/8 mile below the Harrison Street Bridge. THE PRESENT SEIAGE TREATMENT FLINT GENERAL DESCRIPTION The East Lansing sewage treatment plant consists of’a bar screen, pumping station, primary, aeration.and final settling tanks, a digestion tank and a chlorination chamber (not in use at present) and sludge beds. The effluent from the final sett- ling tank discharges into the Red Cedar at the plant site. The present plant was placed in Operation.August 1939. It secures the removal of SS per cent of.the suspended solids (based on records available); and better than 99 per cent of the settleable solids. The balance of the solid material is discharg- ed into the river with the plant effluent. ya plant of this type also removes about 90 per cent of the bacteria from the sewage. 2 When the plant is not overloaded the effluent is very clear but it has been found necessary to by-pass more and more raw sewage through the plant each year as the amount to be handled has increased. To date this has usually occured when the river has been high so that over-pollution of the river has not occured. Gas collected from the digestion tank is used to heat the digesting sewage. an oil furnace is provided in case enough gas cannot be obtained from the digesting sludge. .a gas holder is also provided for storage of excess gas. A sludge bed of 7650 square feet is available to permit sludge from the digestion tanks to dry out. DETAILED DESCRIPTION The sewage enters the plant pump station building by gravity flow thru a 35-inch pipe sewer. It immediately passes thru.a bar screen with clear Openings of 8/4 inch. It then.enters the pump well from which it is pumped to the primary settling tank. There are three electric driven centrifugal.pumps any one or combination.of which may be set in operation. The pump capacities are 1000, 800, and 500 Sll'respectively. The pumps are worn and should be repaired or replaced by new and larger pumps. There are three float controls each of which is connected to start or stop a pump depending on the depth of the sewage in the well. If sewage enters faster than one pump can care for it, the sewage rises and another pump is set in operation and likewise with the third. 5 There are two primary settling tanks each of which is 60 feet long by 14 feet wide, inside dimensions, and has a liquid depth of 9 feet 5-inches. The bottom of the tanks have a slope of i-foot in 60 feet so that the sludge will more easily drain to the sludge chamber and it also makes for better Operation of the mechanical scraper in the tank. The sludge chamber is at the same end as the entrance of the sewage into the primary tank; It is 4 feet 6-inches deep and varies from a 7 foot width on the tap to a 2 foot 3-inch width on the bottom. The sewage enters the tank.thru an 8-inch cast iron pipe. An adjustable weir is provided on the end Opposite the sludge chamber to carry the liquid from the primary to the aerator tanks. The purpose of the weir is to prevent cross current or side movement of the liquid in the primary tankg which would prevent the settling out of the larger particles. The retention period for a four your average is 1.4 hours but this shows a decrease from 1.8 hours in 1940 to 1.2 hours in 1943. It must be understood that the plant was not running at full capacity in 1940. ‘At the point where the sewage leaves the primary settling tank it enters the sludge division and by-pass box where it is canbined with the activated sludge which is being recirculated through the plant. This activated sludge comes from the final settling tank. During the last year the volume of return activated sludge was approx- imately 80 per cent of the sewage flow. 4 from the sludge division and by-pass box the sewage passes through a 18-inch cast iron pipe to the asrators. There are nine aerator tanks which are 83 feet S inches square (inside dimensions) and have a liquid depth of 15 feet 5 inches. The tanks are also provided with a 6 inch Cast Iron pipe for receiving a supernatant liquid from sludge digestion tank. The supernatant is often returned tofihe aerators in excess quantities when it is desired to get rid of heavy grease which is present in some sewage. The aerators are of a mechan- ical type with equipment as manufactured by American‘Iell Ibrks. The retention period in the aerators averages 5.4 hours‘miich varies from.6.7 hours in 1940 to 4.8 hours in 1943. The drop in the retention period has been sready. After passing through the aeratcrs the sewage flows to the final settling tanks through a submerged 80 inch pipe extending across the width of the tank at one and. The sew- age enters at the center of the tank. Due to the retarded velocity of the sewage, the settleable solids are given an opportunity to settle to the bottom of the tank where they are removed to a center hopper by sludge removing mechanism. Prom the final settling tank the sludge passes to the sludge division box where a portion is mixed with the primary tank effluent going to the aerators and the remainder is mixed with the influent to the primary tank and is pumped out with the primary tank sludge to the digester tanks. The present digester tank was converted from an old Imhcff tank. It is 92 feet 8 inches long by 50 feet wide (inside dimensions) and has a liquid depth of 24 feet 3 inches. 5 The length of the tank is divided into three equally size chambers. TREAMT ACCQKPLISHED The degree of sewage treatment accomplished by the present activated sludge plant can best be shown by a brief summary of the four year record of the plant. In gen- eral about 85 per cent of the suspended solids have been: re- moved, and during the entire period of operation of the pre- sent plant seldom was there more than a trace of settleable solids in the effluent. The 301) has been reduced from an average of 79 in the raw influent to 4 in the final effluent during 1943. This is a drop of 95 per cent in 301) which shows that for the sewage treated the operation of the plant has been very efficient. ‘ The settleable and suspended solids not r-oved by treat- ment in the plant remain in the effluent and are discharged into the river. Dy noting the plants accomplishments it can easily be seen that were it not for the ever increasing load the present treatment plant would be more than ample for the city's needs. . The suspended solids in the raw sewage coming into the plant averaged 136 ppm and the suspended solids in the final effluent going into the Red Cedar River averaged 16 ppm or a total reduction of 88 per cent in suspended solids. Chemical analysis of influent and effluent seaples of the present sewage plant are given in Table nod. 5 Table No. _1_. Month 310.330 Snap?nt.le:lmS011dl 5 Day BOD Detefitilgggelgeriod Year lillion Raw an Per Raw P an Per Pri- Aera- Final 1943 Ga1.Per Sew- Efflu-Cent Sew- Efflu-Cent mary tion Settl- Day age ent Remov-age ent Remov-Sett- Tanks ing a1 a1 ling Tanks _ Tanks Jan. 1.863 155 16 89 96 7 93 78 288 138 Feb. 1.787 127 19 76 74 4 90 81 300 150 Ear. 1.772 161 16 88 64 5 91 S2 276 150 tapr. 2.026 190 24 82 90 5 92 71 288 142 as: 1.410 61 10 83 41 4 89 90 321 132 June 1.925 99 13 S4 66 3 90 75 280 138 July 1.909 120 13 88 S4 5 93 76 258 138 .aug. 1.795 117 10 88 S7 2 96 68 300 150 Sep. 1.754 106 22 76 81 4 94 78 301 132 Oct. 1.820 166 21 S7 98 3 97 77 312 144 Dov. 1.876 141 16 87 78 3 96 77 287 138 Dec. 1.792 186 18 95 9S 5 93 80 295 144 .Avg. 1.838 136 16 88 79 4 95 79 291 118 THE RED- cEELR RIVER The flow in the Red Cedar River is generally very low during the summer months of the year. and if the sewage of the cities bordering the river are not completely treated the river will become very highly polluted and contaminated. At the present time the river is polluted. The location of the river below the plant is through a residential and recreational area, which.makes it very desirable to maintain it in a natural clear condition. The river first passes adjacent to the Lansing Red Cedar Buni- cipal Golf Course, thence adjacent to a residential area contiguous to Lansing, thence through.Potter Park. a munici- pal park of the City of Lansing, and thence through a portion of the City of Lansing to its junction with.the Grand River. In order to determine the conditions which may result in.a variable river flow the flow records of the Red Cedar River have been tabulated in tablet!g;_§. The values were obtained from the united States Geological Survey Records from.a continuous recorder station established 300 feet up- stream from Term Lane Bridge on the nichigan State College Campus in larch 1931. The values in the table'§2L_§ show the number of days in each year and for the entire period during whidh the Red Cedar River flows were of certain values. These values are from the‘Snited States Geological Survey Records 193141940. The records are valuable in showing time during which the sewage treatment plant may be affected by high water. 8 lo sanitary surveys have been made on the river since 1938 and as that was before the present plant was put into operation the values obtained would have no bear- ing on the present design. 9 Red Cedar River Discharge Records at East Lansing Ayersge Monthly Discharge in Cu. It. per Sec. (Prom 8.8.8.8. continuous Recorder Records) Tear MOnth gfi Jan. reb. Mar. Lpr..lay June Julzgdug.Sept.Oot.Rov.Dec. 1931 84 62 53 66 40 14 29 29 66 73 1932 215 222 225 290 330 143 34 40 183 128 199 263 1933 294 183 321 689 354 62 31 30 26 121 82 115' 1934 121 45 59 465 65 26 6 6 15 17 23 1935 32 69 655 114 142 134 42 29 37 25 65 65 1936 52 160 478 212 104 36 17 11 25 1937 137 147 71 811 376 726 1938 115 117 490 206 215 103 1939 39 237 339 536 100 88 1940 29 29 251 266 95 247 91 94 114 114 352 1941 298 148 278 334 100 . 64 17 16 39 114 96 1942 84 180 912 253 99 228 57 55 34 64 202 368 1943 297 683 666 260 1006 449 100 56 69 65 24 42 45 36 26 26 26 29 14 16 26 33 87 arrz§ 10 Table No. 3 Tiae for which Flows are as Indicated from 0.8.6. 8. Con- tinuous Recorder Records, Years 1931-1940. o. co Gage Elev. 824.96 5.5 Gage Elev. 827.26 0.1. 8. Gage Reading No. of Per Cent For Higher Days of Time 0. l‘. 3. 0-6 0 6-10 2. 98 . 74 2. 4 10-20 3. 08 . 357 11. 7 20-30 3. 14 390 12. 8 30-60 3. 24 , 486 15. 9 50-100 3. 45 638 20. 8 100-200 3. 79 485 15. 9 200-500 ‘4.07 223 7.3 300-400 4. 30 110 3. 6 400-500 4.55 88 (2.9 500-1000 5. 53 150 4. 9 Over 1000 34 1. 6 11 romnrrcs smr . In determining the population of East Lansing which is very important in determining the enlargement of'the present plant, the following methods were used, arithmet- ical, geometrical and graphical comparison. The figures for the above are given below. The figures up to 1940 are taken.froa the census reports. Data for.hrithmetic Curve Year Pepulation 1910 802 1920 I 1889 1930 4389 1940 5839 During the 10 year period from 1930 to 1940 an increase of 1450 was registered. By applying this same figure for successive decades the population would be 1950 7289 1960 8739 1970 10189 Data for Geometric Curve (Basis 1930-1940 Census) Increase equals 5839 - 4389 - 1450‘1hioh is an in- crease of 33 per cent for the decade. Applying this to ' previous figures the population would be 1950 7764 1960 10384 1970 13739 . l any -. - - -- - 12 The third method used was the graphical comparison and the cities East Lansing was compared with and their respective pepulations are Haunt Pleasant llidland Grand Haven 1910 3972 2527 6856 1920 4819 5483 7205 1930 5211 8038 8345 1940 8413 10329 8799 East Lansing differs somewhat from the cities listed as it is almost completely residential. This peculiar- ity tends for very highly developed residential areas. 13 Michigan State College In determining the enrollment of the college for the future. the curvilinear method was used. This does not offer any exact data for the fluctuations are very great depending upon the economic standing of the country. Other methods were considered impractical to use. Cellege Enrollment Year Population Year Population 1922 1611 1935 4006 23 1609 36 4627 24 1873 37 5212 26 2314 38 5835 26 2534 39 6660 27 2800 40 6776 28 2813 41 6356 29 3019 42 6331 so 3211' 43 3484 31 3299 44 3821 32 3139 45 5284 33 2794 46 13000 54 3323 Iron Graphs 1 and §_it can be seen that the predicted population for Michigan state College and East Lansing will be 26,500. The large enrollment at the college in 1946 was considered abnormal and was not given very much weight in determining future enrollments. It is predicted that the enrollment will begin to drop off in three years and gradually approach the predicted enrollment as shown in Graph 2, which sets the college enrollment as 13,500 in 1970. .' . 44.11! .< .m .D 5 32:2 ruz. yr... 0... 8:53 2 . .< .m .D 5 ~32 IUZ. H72. Oh. Gum—<30“ 8 .g... 5" . 16 Activate Sludge Plant General data Contributing Pepulatien 25,500 Quantity of Sewage per capita per day 126 Gal. Combined Sewer System Plant effluent to be discharged into Red Cedar River l‘low of Sewage 125 x 25,600 1,000,000 = 3.18 Million Gallon Per Day Use 3. 2 "Million. Average Plow in Gal. Per Minute 3.200.000 ~ : 2220 Gal. Per Minute 24:60 Primary Settling Tanks Present Capacity lumber of Tanks 2 2 Size of Tanks = 60' x 14' Liquid Depth 3 9. 26' 216011419. 25 = 16.540 Cu. It. Detention Period 2 hours based on average flow of 2220 Gal. Per Minute. Capacity Required 2,220 2.120 : 35,620 on. It. 7. 48 17 Increase in volume of Primary Settling Tanks Needed. 36.620 cu. ft. Capacity Reg'd 15,540 7 ' Capacity in Present Plant 20.080 cu. ft. needed Using a liquid depth of 9.26 feet this will require 2170 square feet of surface in tanks or 2 tanks 17 x 63.5 ft. Use 2 tanks 17 x 64 x 9.25 = 20,100 cu. ft. .Aeration Tanks Present plant has down draft mechanical asrators. They have operated very efficiently and economically for long periods. The same type will be used in flhe new addition. Period of aeration = 6 hrs for average flow. .Additional allowance for pumped return sludge 35 Per Cent Method of aeration — Mechanical down draft type aerators Plow =‘ 2,220 081 Per Minute. Present Plant. Ho. and size of tanks 9 at 23'-3"xS3'-3' with a liquid depth of 13' 6” Total Volume 65,677 cu. ft. Capacity’Required 2,220 x 60 x 6 x 1.36 = 144,500 cu. ft. 7.48 Increase in.seration Tanks 144.500 cu. ft. req'd for new plant 65,677 cu. ft. capacity of present plant. 78.823 cu. ft. required. 18 Using a liquid depth of 13' 6”; 5828 sq ft of Tank is needed. Use 2 units 60 r 120 feet with a liquid depth of 13' 6". This gives 6.000lsq. ft. of tank. It was considered advisable to use rectangular tanks rather than circular tanks to save space and to decrease cost by using less concrete which is made possible by putting tanks adjacent to each other with a common wall. Pinal Settling Tank Detention Period 2 hours. Sewage flow = 2.220 Gal Per Minute plus 36 per cent returned to aerator for seeding of primary tank effluent. Total Plow==2.997 Gal per min. 'Use 3.000 Gal. per min. Present Plant Capacity No. of tanks 2 Size of tanks 34' square with liquid depth of 10'-0" Vblume of Present Tanks 23.120 cu. ft. Capacity'Required 3.000 r 120 : 48.080 cu. ft. 7.48 Increase in Final Settling Tank 48.080 cu. ft. req'd for new plant 23.129 7 7 Capacity of present plant 24,960 cu. ft. required Using a liquid depth of 10 ft. 2.496 sq. ft. of tank are needed. If the tank is made circular it must have a diameter of 67 ft. . 19 Sludge Digestion Tanks The present tank which was converted from an Imhcff Tank has a total volume of 54.800 cu. ft. It is desirable to have a minimum of 6 cu. ft. per capita to insure appre- val by Michigan State Health Department. Capacity Required 25.500 x 6 = 153.000 cu. ft. Increase in Digestion Tanks necessary 153.000 - 54.000 = 90.200 cu. rt. Gas Storage Tanks The present tank is 16 ft. in diameter and lO'-6' high providing a volume of 2.110 cu. ft. .as the plant will be approximately twice its present size after the addition is made, the total volume for gas storage should be doubled. Another tank of the same size is required. Sewage Pumps The pumping capacity of the plant should be large enough to handle the maximum flow. The array of pumps should be such that it will have great flexibility to meet various rates of flow. With an expected maximum flow of 5.300 Gal. per minute and with the present pumps which have a capacity of about 2.000 Gal. per minute; pumping should be provided for at least another 1.600 Gal. per minute. a 1.000 and 600 Gal. per minute centrifugal pump is suggested. Another 1.000 Gal. per minute pump should be provided for stand-by equipment. 20 Sludge Pumps The present plant has 1 - 50 GP! raw sludge pump and 2 - 225 GB! activated sludge pumps. The pump capacity should be doubled by duplicating present equipment. Chlorination Units The present tank is a Horizontal-flosoarcund the end baffle type and has a capacity of 2.500 cu. ft. Basis for Design Detention Period = 20 minutes. Flow = 2.220 Gal. Per Minute. Capacity Required 2.220 x 30 3 5.960 one ft. 7.48 Increase in cu. ft. Necessary 5.950 - 2.500 = 5.400 cu. ft Using a liquid depth of 8 feet another unit 21' x 21' should be constructed. Sludge Beds Although the use of sludge beds requires a great area it is considered advisable to use this method as the pro- perty for the same is available at no cost. An area of 1.5 sq. ft. per capita will eventually be needed unless some of the beds are covered so that sludge may be dried in the sinter and spring months. If 1.0 sq. ft. is provided at the present tflme for each person. based on the 1970 pepu- lation. ample drying space will be provided for the next decade. 21 DESIGN 01‘ 23mm Tm Cross-sectional View of wall ~‘[ “if.” 5w Ame Design of walls To design the wall a cantilever section will be used. which will support the pressure of the sewage. The liquid depth is 9.25 feet. ‘1‘ a, P- “a“ ‘8 4 “a I amé ._ ‘ Total Pressure on wall from sewage (per foot length of wall). P: ' I he 2 2 P: 52.4 1 £9.25) 2 P: 2.668 lbx. In a cantilever wall with no surcharge the resultant acts at the lower third point as required by the condition of hydro- static pressure variation. laximum moment will be at the bottom of the wall and is 28 I: 2111 5 I: 2668 x 9.25 x 18 5 ll : 98.700 in lbs. 111an thickness of the wall is d’i I where ll= Haximum moment R x b R: 157 (from Reinforced Concrete Design by ‘2: 93 700 Sutherland and Reese) Isl ‘ I; b: lidth of wall. 12" d = 6 inches Minimum thickness for tanks should be 12 inches. so we will use 12 inches. Using a cover of 1.5 inches over the steel on both sides our effective\depth is 12 - a x 1.5 9 inches. Check for Shear v: 7 where v: allowable shear b x 3 x d V: Total pressure on wall 3: 0.875 Substituting values d: effective depth v: 2668 12 1 e875 I 9 v=28.5 p.s. i. Allowable shear 0.12 x 2000: 240 p.s. 1. Therefore the wall is safe for shear. Steel For the amount of steel necessary use the formula 23 is -.- 16.1 d Where is: Area of Steel 13 x X I = Haximum noment r.-=zo.ooo p.s.i. J 3 as 875 By substituting values d= thickness 9 inches is = 98 I700 25.505; 875x§ Ls =.625 sq. in. Use 5/4" round bars spaced at 6" center to center. Check for bond. applying formula where 11: unit bond Eo=tota1 perimeters of bars 1 = 0. 875 d= 9 inches Substituting into formula u= 2668 4.72 x .875 x 9 u = 72 p.s. i. Allowable bond is 0.05 x 2.000: 100 P.s.i. Therefore the wall is safe for bond. £93225: Using the equation 3 =.__AE_¥_£L___. where I. =length in inches bars 3° x u are to extended Substituting values 1,: .525 x 20.000 4e72 x 100 L: 26 inches or 20 bar diameters. 24 Tem erature Stee To overcome pressures due to change in.temperature and shrinks age. horizontal reinforcemmt is required. The usual amount being a minimum of 0.002 of the cross-sectional area of concrete. As : .002 x 10.76 x 12 x 12 10.75'= total height of is = 5.1 square inches ‘ wall. Use 5/8” Round Bars at 12 inches center to center. Other Considerations The pressure on the wall varies as the depth of the sewage in the tank. therefore it is not necessary to carry all the main reinforcing to the top of the wall. The pressure varies from zero at the top of the wall to a maximum on the bottom. 0n the basis that the pressure varies as the distance from the top of the tank cubed all vertical bars do not have to extend to the top of the wall. Using the basis given above the amount at the midpoint of the wall is 1/8 of the Maximum Homent or 12,557 in. 15-. As-= .l f. x J x d is = 12. 557 20.000 x .875 x 9 AI = 0.076 sq. 111. Therefore every other bar can be extended only half way up the wall giving an area of 0.44 sq. in. which is more than ample. The possibility that a tank may have to be drained thus allow- ing the pressure to act in the opposite direction due to ex- terior pressure of earth or sewage in the adjacent tank requires that we put in extra steel. .ABsuming the exterior pressure to 25 be equal to the interior pressure we shall put the same amount of reinforcing on both sides of the tank wall. Design of the Base Slab (Maris—C's— — gm m d ”$1,, [Dra- ‘g. . a. s» k H I f T T t 1 (d6: 62.4‘ 7" 438 /&’.r fer syn/OZ! Deg] .. w den am In the design of e slab for t e base of the tank the slab acts like a simple beam that is supported on two ends with the principal steel running in the short direction. The di- mensions of the base slab are 64 x 17 feet and is going to have a pressure acting on it due to 7.0 feet of hydrostatic head. It is assumed that the slab is 7 feet below the ground water line. Pressure on the base I“: 62.5 x 7 -l = 458 lbs. per sq. ft. Considering both ends of the slab as fixed use a moment of 1/12. ‘ = l/leIx 12 Substituting values = 1/1214551 (17)2x 12 I = 126.682 1n. lbs. 0'. To the minimum thickness of slab use formula Rxb where R = 157 b ' 12 ,3. 135.500 157 x 12 d = 6.7 inches a thickness of 12 inches is suggested as a minimum for tank walls, therefore we will use 12 inches with an effective. depth of 9 inches. Steel in base slab. is: 1 f. x J xd 00.000 x .015 x 0 AI = 0.805 Use 6/4" Round Dare at 6 inches center to center. This pro- vides 0.88 sq. in. which is more than sufficient. Temperature steel will run the length of the tanks. Using the same basis as was used for the wall design we will use 5/8' Round bars at 12' center to center. Check for shear V: V bxixd , . 450: 0.5 12x .075: e ' = 39e‘ pe.e1e Allowable shear is 240 p.s. i. therefore the slab is safe. 27 Check for bond of steel. u = 7 30 x J x d u _ 458 x 8.5 5.5 x .875 x 9 n = 86 De 8. 1e .11lowable bond is 100 p.s.i. therefore slab is safe for bond. 28 Sludge Storage Place ig_Prima£z Tank. Specific Gravity 1.01 Sludge Moisture Content .95 Average Flow of 5.2. M G D 6 hours time between pumping Assume 55% Removal of suspended solids Suspended solids - 200 P P I Volume Required 5.2 x 200 x 55 x 6 = 255 cu ft .05xl.01 x 24x7.48 Percentage of flow through present plant 15.540 x 100 3 45.64 55.620 Volume Required in New.addition (255) x (1.00 - .456) = 155 cu ft. Using 4 heppers 7' x 8.5' at top and 2.25 feet square at bottom with a depth of 4.5' gives a volume of 491.16 cu ft. ' 1v:41%(7x8+2.2512.25+rfia5x2.25x2.2€> V = 491.16 This is more than sufficient for it allows a detention period of 12.6 hours. This size hopper was used so that the entire width of tanknwould be used and the slope of the sides would be sufficientto prevent the sludge from sticking to it. Iglgt’Channel Tank.is 17' wide try 2 inlets. The inlets to be 4.25' from each end of tank and 8.5 between centers. velocity through Openings to be 2 feet per second. 29 Flow Present Plant can handle 15.540 x 7.40 s 975 e r a 120 Flow Addition to Plant must handle 2.220 - 975.: 1245 G P M'er 2.78 C.F.S. Cross-sectional area of each inlet 2.78 4 x2 =e 3‘8 BQe ft. Size Pipe to use A : d 4 . 0348 8 e514 dz 4 d 3 .66 feet use 8" pipe.Area .549 sq. ft. 929.23. In designing outlets at least one foot of weir should be provided for every hundred thousand gallons of flow per day; With a daily flow of 5.2 Gallons 56.4 per cent of which.will be handled by the new addition requires a total length of*weir 52 x .564 = 18.04 feet. The tanks are 18' so two weirs each 17' long providing a total weir length of 68 ft. By using a weir of’longer length.the velocity of the effluent over the weir will be decreased whidh is important for the further we decrease the velocity. the smaller is the amount of solids that will be carried out with the effluent. .After going over the weir the effluent enters the outlet trough which must have 2.x .548 = .676 sq. ft. in area with an effluent velocity 50 of 2 feet. In this design a trough 1.5' x 1' will be used. The weir on this trough will be adjustable from the water surface level by i 2.0 inches. Scum Trough To prevent the accumulation of floating matter on the primary tanks and its passage over the effluent weir. scum boards are provided. The upper lip of the scum trough will be 2% inches above the normal water surface. The inside dimentions of the trough will be 9" x 6" and will slope towards the side so that after the some is raked into tha it may be drained off. 51 Estimate 9; 9223 Primary Settling Tanks Concrete 170 cu. yds e 25.00 Steel 14.40% s 55¢ per pound valves. Piping, Rails Sludge Removing Mechanism-2 e 1700 Total - .Aeration Tanks - Concrete 800 cu. yds. c 25.00 Steel 95.400# 0 51¢ per pound valves. Piping. Railing Aerators 10 units 0 1.500 Total - Pinal Settling Tanks - Concrete 220 cu. yds. valves, Piping Rails Weirs Sludge Removing Mechanism Total - Sludge Beds - Concrete 80 cu. yds O 20 Chlorination Chamber - Concrete 90 cu yds c 25.00 Steel 55283} 0 25¢ per pound Valves. Piping. manhole Cover Total - Gas Holder - l - 16 ft diameter steel tank Sludge Digester Tank - (following page) 4,250.00 580.00 550.00 5,400.00 8,580.00 20,000.00 0,559.00 550. 00 15,000.00 58,689.00 5,500.00 500.00 5,500.00 11,500.00 1,600.00 2,250.00 187.00 60.00 2,497.00 5,000.00 Sludge Digester Tank Concrete 560 cu. yds e 9,000.00 020.1 59.52% 0 5i: cents per pound 1,555.00 Gas Collector. and other equipment 5,500.00 Pipes. valves. etc. 500.00 Total - 14,165.00 2 - 1.000 G P l Sewage Pump 2 Motor 2,000.00 1 - 500 G rzu Sewage Pump 5 Motor 750.00 1 - 400 G P I'Raw Sludge Pump 0 Motor 600.00 l-5OGPI " " " " " 750.00 Chlorinating Equipment 2,000.00 Heating Equipment 5,500.00 Excavation 11,611 0 50¢ per cu yd. 5,805.00 Meters for measuring sewage 1,000.00 Miscellaneous valves and piping 1,500.00 Engineering and Contingencies 9,770.00 cam roan.- $107,506.00 Bibliography. Reinforced Concrete Design, by Sutherland 5 Reese. Second Edition - John.li1ey’& Sons. Sewerage and Sewage Disposal Text Book, by Metcalf a lady. Second Edition - HrGraw - Hill Book Company. 'later Supply and Sewerage, by Steel. Tirst Edition. McGraw - Hill Book Company. Bulletins in Reinforced Concrete Design of the Portland Cement Association. 5.. ,\s __"_.‘ ‘4‘ V” f3“. 1......2 - '- |\J 7" ”4...“..10. ' \ O.“ 4 2 .1 v. ....ev‘ . .~ . ~ . ,..-.p..‘ _ its . a c . . . . l a ..a I‘K. Ow ll. .‘l .I , ‘ a , w. . a. ' h ‘ u\ . .1 .. .. i . a ..v {a t O. .. . r .u. _ ' . 7.V . c 4. 2.2. . .. .' a J Wu a a 1.4 .. a at :1 .. . N .. 7 1 . 5%... “I..m.e1\ net 2 .. 25" 4 1M 4‘. .a .u’. .ak‘ ’. I .. . a a s 0.1 . f ., .1. 551...; .. . .l as . tw.‘vw.e . I \ I u . a»: .3" e. 5 O 1” .a .4 9.4.2. 2: CéODZ mqbam C2:.