1. You are provided the following information about a municipal wastewater treat
ID: 794255 • Letter: 1
Question
1. You are provided 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 0.05/day, and the microbes reach half of their maximum growth rate when the BOD5 concentration is 10 mg/L. There are 150,000 people in the community (their wastewater production is 225 L/day-capita, 0.1 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 biological reactor, 15,000 mg/L in the secondary sludge, 200 mg/L in the plant influent, and 100 mg/L in the primary clarifier effluent. SRT is equal to 4 days.
(a) What is the design volume of the aeration basin (m3)?
(b) What is the plant
Explanation / Answer
F/M = 0.1 kg BOD5/kg MLVSS.day
mean cell residence time or sludge retention time (SRT), qc, d
qc = V X
QwXr + (Q-QwXe)
where SO and Se are influent and effluent organic matter concentration respectively, measured as BOD5 (g/m3), X, Xe and Xrare MLSS concentration in aeration tank, effluent and return sludge respectively, and Qw= waste activated sludge rate
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