This document contains 7 questions from an environmental engineering homework assignment. The questions involve calculating BOD levels and theoretical oxygen demand of ethanol in wastewater. Additional questions calculate TSS, VSS, TDS and FDS levels based on compound concentrations. Other questions determine the fraction of maximum oxygen consumption after 5 days, the rate constant and half-life for an ultraviolet ozonation reaction, and the monthly chlorine usage for a water treatment plant.

1. EG-CE 441 Environmental Engineering
Homework #3
(Due 10/15/13)
(Show your calculations)
1. A wastewater stream has a BOD5 of 150 mg/L, and the BOD rate constant is 0.20/day (base e).
The BODultimate of this wastewater = 237 mg/L.
The BOD7 of this wastewater =179 mg/L.
2. Calculate the theoretical oxygen demand of 10-4M ethanol, CH3CH2OH.
ThOD = 9.6mg/L.
3. Use the information given in the following table to answer the question:
Compound
Sodium chloride
Sand and clay
Coffee grounds
Alcohol
Concentration
(mg/L)
10
90
30
80
Dissolves?
Burns or volatilizes at 550 oC?
Yes
No
No
Yes
No
No
Yes
Yes
TSS = 120 mg/L.
VSS = 30 mg/L.
TDS =10mg/L.
FDS = 10 mg/L.
4. A wastewater stream is being discharged into a river that has a temperature of 15 oC. What
fraction of the maximum oxygen consumption has occurred in five days if the BOD rate constant
determined in the laboratory under standard condition is 0.25/day (base e)? 48.6%
5. A constant volume batch reactor was operated to provide data for determination of reaction rate
constant for ultraviolet enhanced ozonation of a synthetic organic compound. The duration of the
batch reaction was 1 hr and the concentration of the organic compound was reduced from 200
µg/L to 10 µg/L. If the reaction is assumed to be first-order with respect to this synthetic
compound, then determine the rate constant for the oxidation reaction in 1/hr. 3.0 hr-1
6. What would be the “half-life” of the compound in the reactor in question #5? 0.231hr
7. The chlorine dose for a 10 MGD water treatment plant is 8 mg/L. The peak factor is 1.8.
Determine the monthly usage of chlorine at this plant. 2.0x104 lbs/mo