You are provided with the following information about a municipal wastewater treatment plant. This plant uses the traditional activated-sludge process. Assume the microorganisms are 55 percent efficient at converting food to biomass, the organisms have a first-order death rate constant of 0.050/day, and the microbes reach half of their maximum growth rate when CE 3059 Page 2 of 2 the BOD5 concentration is 10.0 mg/L. There are 150,000 people in the community (their wastewater production is 225 L/day-capita, 0.10 kg BOD5/capita-day). The effluent standard is BOD5 = 20 mg/L and TSS = 20 mg/L. Suspended solids were measured as 4,300 mg/L in a wastewater sample obtained from the aeration tank, 15,000 mg/L in the secondary sludge, 200 mg/L in the plant influent, and 100 mg/L in the primary clarifier effluent. The mean cell residence time is 4.0 days. a. What is the design volume of the aeration basin in cubic meters? b. What is the aeration basin detention time? c. How many kg of secondary dry solids need to be processed daily from the treatment plant? d. If the sludge waste flow (Qw) is increased in the plant, will the solids retention time go up, go down, or remain the same? e. Determine the F/M ratio in units of kg BOD5/kg MLVSS-day show all work pleaes
You are provided with the following information about a municipal wastewater treatment
plant. This plant uses the traditional activated-sludge process. Assume the microorganisms
are 55 percent efficient at converting food to biomass, the organisms have a first-order death
rate constant of 0.050/day, and the microbes reach half of their maximum growth rate when
CE 3059 Page 2 of 2
the BOD5 concentration is 10.0 mg/L. There are 150,000 people in the community (their
wastewater production is 225 L/day-capita, 0.10 kg BOD5/capita-day). The effluent standard
is BOD5 = 20 mg/L and TSS = 20 mg/L. Suspended solids were measured as 4,300 mg/L in
a wastewater sample obtained from the aeration tank, 15,000 mg/L in the secondary sludge,
200 mg/L in the plant influent, and 100 mg/L in the primary clarifier effluent. The mean cell
residence time is 4.0 days.
a. What is the design volume of the aeration basin in cubic meters?
b. What is the aeration basin detention time?
c. How many kg of secondary dry solids need to be processed daily from the treatment
plant?
d. If the sludge waste flow (Qw) is increased in the plant, will the solids retention time go
up, go down, or remain the same?
e. Determine the F/M ratio in units of kg BOD5/kg MLVSS-day
show all work pleaes
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