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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
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- 8000 mg/I
- 25000 mg/1
- 33800 mg/1
- 42600 mg/1
Correct Option: B
| Total solids in sample = | ||
| vol. of sample test |
| = | × 106 = 33800 mg/l | |
| 75 |
Inorganic fraction
| inorganic solid in sample = | × 106 = 8800 mg/l | |
| 75 |
Organic fraction = Total solids – Inorganic solids
= 33800 – 8800 = 25000 mg/l
