An analysis for determination of solids in the return sludge of activated sludge process was done as follows: (1) A crucible was dried to a constant mass of 62.485 g. (2) 75 ml of a well-mixed sample was taken in the crucible. (3) The crucible with the sample was dried to a constant mass of 65.020 g in a drying oven at 104 C. The crucible with the dried sample was placed in a muffle furnace at 600 C for an hour. After cooling, the mass of the crucible with residues was 63:145 g. The concentration of organic fraction of solids present in the return sludge sample is

An analysis for determination of solids in the return sludge of activa

1.	An analysis for determination of solids in the return sludge of activated sludge process was done as follows: (1) A crucible was dried to a constant mass of 62.485 g. (2) 75 ml of a well-mixed sample was taken in the crucible. (3) The crucible with the sample was dried to a constant mass of 65.020 g in a drying oven at 104 C. The crucible with the dried sample was placed in a muffle furnace at 600 C for an hour. After cooling, the mass of the crucible with residues was 63:145 g. The concentration of organic fraction of solids present in the return sludge sample is
A.	8000 mg/I
B.	25000 mg/1
C.	33800 mg/1
D.	42600 mg/1
Answer» C. 33800 mg/1

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