Multiple choice

A conventional Activated Sludge Plant treating 1000 m3/d of municipal waste water disposes of its anaerobically digested sludge on relatively impervious farmland. Use the following data:

1. Raw Sewage SS = 225 mg/I (70% volatile)

BOD = 190 mg/I (Excess activated sludge returned to primary) | | 2. Primary Setting| SS-50% removal BOD-30% removal| | 3. Excess Activated Sludge applied (80% Volatile of total)| 0.4 g VSS produced per g BOD| | 4. Anaerobic Digester| VSS reduced 50% Digested Sludge Concentration – 60% Sludge Specific Gravity-1| | 5. Application on farmland| 2 m3 /ha.d|

Total volatile suspended solids to be anaerobically digested (kg/d, VSS) shall be

  1. 133

  2. 168

  3. 233

  4. 245
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A Correct answer
Explanation

Total VSS is the sum of VSS from primary sludge and excess activated sludge. Primary sludge VSS is calculated from SS removal and volatile fraction. Excess activated sludge is 0.4 * BOD removed. Summing these gives 133 kg/d.

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