Domestic Wastewater Treatment Mobilization Construction - AskTOP

EM 1110-3-17211 May 84APPENDIX ASAMPLE PROBLEMSA-1 . Sedimentation .a . Design requirements and criteria . Design a sedimentation unitto provide settling for a sewage flow rate of 4 mgd with suspendedsolids concentration of 300 mg/1 . The following conditions apply :Surface loading rate = 600 gpd/square footSuspended solids removal = 60 percentSludge solids content = 4 percentSludge specific density. = 1 .02b . Calculations and results .(1) Calculate total tank surface area,Surface = Flow Rate = 4,000,000 gpd = 6,666 .7Area Surface Loading Rate 600 gpd/square foot square feetuse 6,670 square feet(2) Using a depth of 8 feet, calculate total volume .V = 8 x 6,670 = 53,360 cubic feet(3) This volume can be divided among three rectangular tanks (inparallel) 20 feet wide and 120 feet long with a length-to-width ratioof 6 to 1 . Two circular tanks (in parallel) 65 feet in diameter wouldalso be suitable . This will provide flexibility of operation duringroutine or emergency maintenance and operations cleaning and repair ofthe units .(4) Calculate weir length requirement assuming three rectangulartanks and allowable weir loading rate of 12,000 gpd/linear foot .Design Flow per Tank = Total Flow = 4,000,000 gpd= 1,333,333 gpdWeir Length/Tank = 1,333,333 gpd = 111 linear feet12,000 gpd/linear foot(5) Compute weight of solids removed assuming 60 percentremoval :