A conventional activated-sludge plant treats 10.0 MGD ofmunicipal wastewater with a BOD concentration of 240 mg/l andsuspended solids of 200 mg/l. The sludge flow pattern is shown inFigure 11-1 of the textbook with a gravity belt thickener toconcentrate the excess activated sludge. Primary and thickenedactivated sludge are pumped separately to the anaerobic digester.The primary clarifier removes 50% of the suspended solids and 35%of the BOD. The primary sludge solids content is 4.0%. Theoperating F/M ratio for the activated-sludge process is 0.3 lb BODper day per pound of MLSS. The solids content of the waste sludgeremoved from the secondary clarifier is 16,000 mg/l; the gravitybelt thickening captures 95% of the solids in the sludge andincreases the solids content of the thickened sludge to 7%.Calculate: a) Flow rate of primary sludge, in gals/day b) Flow rateof thickened secondary sludge, gals/day. c) Flow rate and solidsconcentration of the blended sludge
