Domestic Wastewater Treatment Mobilization Construction - AskTOP

EM 1110-3-17211 May 84Table 12-1 .Aerobic Digestion Design ParametersParameter Value RemarksSolids Retention Time, , 10-15a Depending on temperature,days type of sludge, etc .Solids Retention Time,daysVolume Allowance,cubic feet/capita15-20b3-4VSS Loading, pcf/day 0 .024-0 .14 Depending on temperature,type of sludge, etc .Air RequirementsDiffuser System, 20-35a Enough to keep the solids incfm/1,000 cubic feetsuspension and maintain a DObetween 1-2 mg/l .Diffuser System, >60bcfm/1,000 cubic feetMechanical System, 1.0-1 .25 This level is governed byhp/1,000 cubic feet mixing requirements . Mostmechanical aerators in aerobicdigesters require bottommixers for solidsconcentration greater than8,000 mg/l, especially ifdeep tanks (>12 feet) areused .Minimum DO, mg/l 1 .0-2 .0Temperature, degrees C >15If sludge temperatures arelower than 15 degrees C,additional detention timeshould be provided so thatdigestion will occur at thelower biological reactionrates .VSS Reduction, percent 35-50Tank DesignAerobic digestion tanks areopen and generally require nospecial heat transferequipment or insulation . Forsmall treatment systems (0 .1mgd), the tank design shouldbe flexible enough so thatthe digester tank can alsoact as a sludge thickeningunit . If thickening is to beutilized in the aeration tank,sock type diffusers should beused to minimize clogging .Power Requirement,BHP/10,000Population Equivalent 8-10aExcess activated sludge alone .bPrimary and excess activated sludge, or primary sludge alone .Source : EPA Process Design Manual for Sludge Treatment andDisposal, October 1974 .12-3