Environmental Engineering Flashcards
Glutamic acid (C5H9O4N) is used as one of the reagents for a standard to check the BOD test. Determine the
theoretical oxygen demand of 150 mg · L−1 of glutamic acid. Assume the following reactions apply
212 mg · L−1
The company you work for plans to release a waste stream containing 7.0 mg · L−1 of benzaldehyde.
Assuming that benzaldehyde degrades according the reaction:
C7H6O + 8O2 −→ 7CO2 + 3H2O
calculate the theoretical carbonaceous oxygen demand of this waste stream (in mg · L−1
).
16.906 mg · L−1
If the BOD5 of a waste is 220.0 mg · L−1 and the ultimate BOD is 320.0 mg · L−1, what is the rate constant?
k = 0.233 day−1
The BOD rate constant is 0.233 day−1 for a municipal wastewater. The BOD5 was measured to be
250 mg · L−1. What is the ultimate BOD?
363 mg · L−1
A sample of municipal sewage is diluted to 1% by volume prior to running a BOD5 analysis. After 5 days
the oxygen consumption is determined to be 2.00 mg · L−1. What is the BOD5 of the sewage?
BOD5 = 200 mg · L−1
If the ultimate BOD values of two wastes having k values of 0.3800 day−1 and 0.220 day−1 are
280.0 mg · L−1, what would be the 5-day BOD for each?
Answer: For k = 0.38 day−1
, BOD5 = 238 mg · L−1 ; for k = 0.22 day−1
, BOD5 = 187 mg · L−1
The following data are provided to you:
Seeded wastewater:
Initial DO = 8.6 mg · L−1
Final DO (after 5 days) = 2.1 mg · L−1
Volume of wastewater = 2.5 mL
Total volume in BOD bottle = 300.0 mL
Seeded dilution water:
Initial DO = 8.6 mg · L−1
Final DO (after 5 days) = 7.3 mg · L−1
Volume of seeded dilution water = 300.0 mL
T = 20◦C
Calculate the BOD of the sample (in units of mg · L−1 ).
Answer: 625 mg · L−1
The Waramurungundi tannery with a wastewater flow of 0.011 m3 · s−1 and a BOD5 of 590 mg · L−1 dis-
charges into the Djanggawul Creek. The creek has a 10-year, 7-day low flow of 1.7 m3 · s−1. Upstream of
the Waramurungundi tannery, the BOD5 of the creek is 0.6 mg · L−1. The BOD rate constants (k) are
0.115 day−1 for the Waramurungundi tannery and 3.7 day−1 for the creek. Calculate the initial ultimate BOD
after mixing.
Answer: 9.27 mg · L−1
The initial ultimate BOD after mixing of the Bergelmir River is 12.0 mg · L−1. The DO in the Bergelmir
River after the wastewater and river have mixed is at saturation. The river temperature is 10◦
C. At 10◦
C, the
deoxygenation rate constant (kd) is 0.30 day−1
, and the reaeration rate constant (kr) is 0.40 day−1
. Determine
the critical point (tc) and the critical DO.
Answer: tc = 2.88 days. Critical DO = 7.53 mg · L−1
The discharge from the Renenutet sugar beet plant causes the DO at the critical point to fall to 4.0 mg · L−1.
The Meskhenet Stream has a negligible BOD and the initial deficit after the river and wastewater have
mixed is zero. What DO will result if the concentration of the waste (Lw) is reduced by 50%? Assume that
the flows remain the same and that the saturation value of DO is 10.83 mg · L−1 in both cases.
Answer: DO = 7.4 mg · L−1
Assuming that the mixed oxygen deficit (Da) is zero and that the ultimate BOD (Lr) of the Manco Capac
River above the wastewater outfall from Urcaguary is zero, calculate the amount of ultimate BOD
(in kg · day−1
) that can be discharged if the DO must be kept at 4.00 mg · L−1 at a point 8.05 km down-
stream. The stream deoxygenation rate (kd) is 1.80 day−1 at 12◦
C, and the reaeration rate (kr) is 2.20 day−1
at 12◦
C. The river temperature is 12◦
C. The river flow is 5.95 m3 · s−1 with a speed of 0.300 m · s−1. The
Urcaguary wastewater flow is 0.0130 m3 · s−1.
Answer: Mass flux = 1.14 × 104 kg · day−1 of ultimate BOD
A small lake is surrounded by agricultural land. The lake is 150 m long and 120 m wide. The average
depth is 30 m. The lake is fed by a small pollution-free stream having an average flow rate of 1.5 m3 · s−1.
A herbicide, Greatcrop, is detected at a concentration of 45.2 g · L−1 in the lake. Greatcrop degrades
biologically with a rate constant of 0.22 day−1
. Assuming that the lake is at steady-state conditions and
completely mixed at the time of sampling, what would have been the mass input of herbicide? Assume
that the stream is the only source of water to the lake and that evaporation, precipitation, and seepage can
be neglected.
Answer: 11.2 kg · day−1
Suspended solid present in the waste water generated in blast furnace gas cooling and cleaning plant is removed by
radial settling tank (thickener) using coagulant (lime & ferrous sulphate)
Persons working in cement plants and limestone quarries are more prone to disease like
a. cancer
b. asthma
silicosis
flourosis (bone diseases)
silicosis
Particulates (< 1μm size) remaining suspended in air indefinitely and transported by wind currents are called
a. fumes
b. mists
smoke
aerosols
aerosols
