This document contains instructions for 4 homework problems related to environmental engineering calculations. Problem 1 asks to calculate the volume of an aeration tank given parameters like flow rate, BOD loading, and MLVSS concentration. Problem 2 asks to calculate hydraulic retention times for continuous flow stirred tank and plug flow reactors treating wastewater. Problem 3 provides data to calculate organic loading rate, F/M ratio, and sludge wasting rate for an activated sludge process. Problem 4 gives specifications for a trickling filter to estimate hydraulic loading rate and effluent BOD.

1. EG-CE 441 Environmental Engineering
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2. EG-CE 441 Environmental Engineering
Homework #6
(Due 12/3/13)
1. (Problem 5-24) If the F/M ratio of a 0.4380 m3/s activated sludge plant is 0.200 d-1, the influent
BOD5 after primary settling is 150 mg/L, and the MLVSS is 2,200 mg/L, what is the volume of
the aeration tank?
2. A biological reactor is used to treat wastewater from a small community (Q = 100,000 gpd). The
influent BOD5 concentration to the reactor is 200 mg/L and the required effluent BOD5
concentration is 30 mg/L. The reaction rate constant in the reactor = 0.25/day. Estimate the
hydraulic retention time (HRT) if the reactor is a CFSTR and the HRT if the reactor is a PFR.
3. Use the following information regarding an activated sludge process to find the organic loading
rate (volumetric) in lb/day/ft3, F/M in lb BOD5/d/lb MLVSS, and sludge wasting rate in MGD.
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Design flow rate = 4 MGD
influent soluble BOD5 = 250 mg/L
hydraulic retention = 5 hrs
MCRT = 8 days
MLVSS = 2400 mg/L
Waste sludge concentration = return sludge concentration = 0.8%
4. A trickling filter using plastic media has a diameter of 25 m and a depth of 2 m if the flow rate is
1,600 m3/d and the influent BOD5 is 200 mg/L.
Effluent BOD5
−3( D /
=e
Influent BOD5
QL )
where D = filter depth, m
QL = hydraulic loading rate per unit area, m3/d⋅m2
Estimate the hydraulic loading rate in m3/d⋅m2 and the BOD5 of the effluent in mg/L.