Calculate the size of an anaerobic digester required to treat the sludge from a primary clarifier designed to treat 38,000 m3/d of sewage. The quantity of dry volatile solids removed by the plant is 0.15 kg dry solids/m3 sewage. The sludge contains 95 % of moisture, and has a specific gravity of 1.02. The BOD loading to the digester is 5320 kg/d. The digester has the following characteristics: Solids retention time = 10 days, efficiency of waste utilization = 70%, Y =0.08 kg VSS/kg BOD utilized, kd = 0.03 d-1, digester gas is 65% methane.