Waste Water Engineering online test on “Activated Sludge Process – 2”.
1. Calculate the volume of the aeration tank required for the following data:
Flow: 800 m3/d
BOD: 1000 mg/L
F/M ratio: 0.15(extended aeration)
MLSS : 3500 mg/L
a) High sludge volume index
b) Low sludge volume index
c) Low oxygen demand
d) Floc formation is less
Answer: a
Clarification: Readily biodegradable COD if it is high in the influent, then the sludge volume index will be very high. Also this high level of COD would contribute to the floc formation. This also results in higher oxygen demand.
2. For the removal of BOD through Activated Sludge Process (ASP) what would be the Solid retention time considered?
a) 18 hours
b) 1-2 days
c) 10 hrs
d) 3 days
Answer: b
Clarification: For the removal of BOD through ASP, the solid retention time considered is 1-2 days. However, this depends on the temperature. In case the temperature is very low, then the solid retention time considered would be around 5-6 days.
3. For the conversion of particulate organics through Activated Sludge Process (ASP) what would be the Solid retention time considered?
a) 18 hours
b) 1-2 days
c) 2-4 days
d) 5 days
Answer: c
Clarification: For the conversion of particulate organics through ASP, the Solid retention time considered would be 2-4 days. Particulate organic carbon is defined as those materials that can pass through a filter which is of size 0.7 to 0.22 um. This usually constitutes soil organic matter that includes plant material, pollen etc.
4. For the development of flocculent biomass for treating domestic water through Activated Sludge Process (ASP) what would be the Solid retention time considered?
a) 18 hours
b) 4 days
c) 10 hrs
d) 1-3 days
Answer: d
Clarification: For the development of flocculent biomass for treating domestic water through the Activated Sludge Process (ASP), the solid retention time considered is 1-3 days. In case it is industrial waste water, the retention time considered would be different. The difference is due to the difference in concentration of BOD in the influent.
5. For the development of flocculent biomass for treating industrial water through Activated Sludge Process (ASP) what would be the Solid retention time considered?
a) 18 hours
b) 3-5 days
c) 20 hrs
d) 1-3 days
Answer: d
Clarification: For the development of flocculent biomass for treating industrial water through Activated Sludge Process (ASP), the solid retention time considered is 3-5 days. This is a little higher than that of the Solid retention time required to treat domestic waste water. The difference is because the industrial waste water constitutes higher BOD values.
6. For the removal of nitrogen completely through Activated Sludge Process (ASP) what would be the Solid retention time considered?
a) 3-18 days
b) 1-2 days
c) 12 hours
d) 18 hours
Answer: b
Clarification: For the complete removal of Nitrogen through ASP, the solid retention time considered is 3-18 days. However, this depends on the temperature. In case the temperature is very low, then the solid retention time considered would be around 15-18 days. For higher temperatures, lower solid retention time is considered.
7. For the removal of phosphorous through Activated Sludge Process (ASP) what would be the Solid retention time considered?
a) 18 hours
b) 1-2 days
c) 10 hrs
d) 2-4 days