4-8 hours

24 hours

10 to 15 days

3 months

sludge digestion

sludge disposal

sedimentation

filtration

large area is required for construction

maintenance and operation cost are high

BOD removal is very low

none of the above

4.5 to 6.0

6.5 to 8.0

8.5 to 10.0

10.5 to 12.0

percentage of sludge by volume to percentage of suspended solids by weight

percentage of sludge by volume to percentage of total solids by weight

percentage of suspended solids by weight to percentage of sludge by volume

percentage of total solids by weight to percentage of sludge by volume