You have been retained to design a wastewater treatment plant using
a conventional activated sludge process for a town of 40,000
people. The industrial flow contribution to the sewer system is
300,000 gallons per day. Effluent discharge standards require
effluent BOD5 and total suspended solids concentration of <10
mg/l.
Assume the following design criteria are applicable:
Domestic sewage flow = 100 gal/cap/day (including I/I)
BOD loading = 0.18 lbs/cap/day
TSS loading = 0.20 lbs/cap/day
BOD removal in primary = 33% at surface overflow rate of 1,000 gpd/ft2
BOD loading to aeration basin = 40 lb BOD/1000 ft3
Oxygen required for aeration = 1.1 1bs O2/lb BOD applied.
Aerator oxygen transfer rate = 2.5 lbs O2/hp-hr
MLSS concentration = 2,750 mg/l; MLVSS conc.= 0.8 MLSS conc.
Final clarifier surface overflow rate = 800 gpd/ft2
Question:
Determine the BOD loading to the aeration basin.
Determine the size of the aeration basin (length/width/height) for a 6-hour detention time.
Calculate the F/M ratio.
Determine aeration requirements (number and hp capacity of aerators)
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