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|

Area requirements (ha) for disposal of the sludge on farmland shall be

  1. 2.95

  2. 1.95

  3. 0.95

  4. 0.55
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The digested sludge volume is calculated by accounting for VSS reduction in the digester and the final sludge concentration. Dividing this volume by the application rate per hectare gives the required area.

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