Environmental Engineering Reference
In-Depth Information
8.7
What must be done to decrease the SVI?
8.8
What is the liquid mixture of microorganisms and solids removed
from the bottom of the settling tank called?
8.9
What is the mixture of primary effluent and return sludge
called?
8.10 What are the three things that must be balanced to make the
activated sludge process perform properly?
8.11 What is the major purpose of an activated sludge process?
8.12 Name two types of aeration devices used in the activated sludge
process.
8.13 List three observations the operator should make as part of the
daily operation of the activated sludge process.
8.14 A 2100-mL sample of activated sludge is allowed to settle for 60
min. At the end of the 60 min, the sludge has settled 1200 mL.
What is the SSV
60
of the sample?
8.15 An activated sludge sample has an MLSS concentration of 2240
mg/L. The SSV
30
of the sample is 425 mL/L. What is the sludge
volume index of the sample?
8.16 The operator wastes 0.067 MGD of activated sludge. The WAS con-
centration is 8180 mg/L. How many pounds of activated sludge
solids have been removed from the process?
8.17 Which activated sludge process aerates the return sludge before
mixing it with the influent flow?
8.18 A microscopic examination of the activated sludge reveals a pre-
dominance of rotifers. What process adjustment does this indi-
cate is required?
8.19 Given the following data, calculate the desired pounds of mixed
liquor suspended solids (MLSS) in the aeration tank:
Primary effluent suspended solids = 125 mg/L
Influent flow = 2.2 MGD
Desired sludge age = 5.0 days
Aeration tank = 100 ft × 40 ft × 12 ft
Influent BOD = 230 mg/L
Effluent suspended solids = 14 mg/L
8.20 List three observations that would indicate that the activated
sludge was becoming old.
8.21 What are the major differences between the conditions known as
bulking, rising, and ashing sludge?
8.22 Why is color a less reliable process indicator?
8.23 List the conditions you would expect to observe when the acti-
vated sludge system is operating normally?
