An MSW (Municipal Solid Waste) sample weighs 5 kg. Total energy content of the waste sample collected is 75000 kJ. The moisture content of the waste sample is 20 percent. Assume that the ash content in the sample is 5 percent. The energy content (in kJ/kg, in integer) on ash free dry basis is_

1. The solids content of a stream water sample is to be determined. The total solids content is determined by placing a portion of the sample into a porcelain evaporating dish, drying the sample. at 105°c, and igniting the residue by placing the dried sample in a muffle furnace at 105°C. The following masses are recorded: • mans of empty dish: 50.326 g mass of dish and ignited solids: 50,383 g P=118,400 g - 50,336 g = 68.074 ml mass of dish and sample: 118.400 g mass of dish and dry solids: 50. 437 g a) The total solids content is: (50.437g-50.326 g) b) The total volatile solids content is: c) The fixed solids content is:

An activated sludge system using CSTR with sludge recycle has an influent flow rate (Q°) of 2.5 MGD that contains BOD of 200 mg/L. The volume of the aeration tank (CSTR) is 0.6 million gallons. The MLVSS (assume this is X,) in the aeration tank is 2000 mg VSS/L and the decay rate (b) is 0.1/day. The effluent from the secondary clarifier meets NPDES standards for suspended solids and BOD. The concentration of the settled sludge exiting the bottom of the secondary clarifier is 15,000 mg VSS/L. The sludge waste flow rate (Q") is 1 % of the influent flow rate, and the effluent flow rate (Qª) is ~99% of the influent flow rate. а) What is the hydraulic retention time, 0 (d)? b) What is the solids retention time, 0x (d)? Activated sludge with recycle с) What is the F/Ma ratio?

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