Fall 20xx
CE 310 Sample Third Term Exam
Closed Book Portion
B.A. DeVantier
Matching. (2 points each) Put the letter of the description on the right which best describes one of
the terms on the left. No letter may be used more than once.
_G__ Slurry scrubber
A. Primary air pollutant produced in combustion of sulfur
containing hydrocarbon fuels.
_L__ Grit chamber
B. Primary air pollutant produced in any combustion process
in air.
_J__ Trickling filter
C. Secondary air pollutant produced due to chemical
reactions with the aid of light.
_B__ NOX
D. Primary air pollutant produced by incomplete combustion
of hydrocarbon fuels.
_A__ SOX
E. Primary air pollutant consisting of small non-gaseous
particles.
_I__ Sludge recycle
F. Primary air pollutant consisting of chemicals which
evaporate easily.
_E__ Particulates
G. Air pollution control device for removing SO2.
_C__ O3
H. Pumped flow return from secondary clarifier to attached
microbial mass.
_F__ VOCs
I. Pumped flow return from secondary clarifier to aeration
tank.
_H__ Trickling filter recirculation
J. Wastewater treatment unit using a stationary (fixed
position) fixed film biological process.
_M__ Maximum specific growth rate K. Wastewater treatment unit using a suspended growth
biological process.
_O__ Half velocity constant
L. Wastewater treatment unit using settling to remove sand.
_P__ Electrostatic precipitator
M. Monod model constant having units hr-1.
_D__ CO
O. Monod model constant having units mg/L.
_K__ Activated sludge
P. Air pollution control device to control particulates.
Multiple Choice. (2 points each) Circle the letter of the phrase which best completes each sentence
below.
1. Primary wastewater treatment includes
A. grit removal, screening, and primary sedimentation.
B. primary settling, secondary settling, and sludge drying.
C. biotreatment, digestion, and chlorination
D. activated sludge treatment, chlorine contact, and discharge.
2. Two of the most important parameters regulated in the Secondary Treatment Standards are
A. TKN and ThOD.
B. BOD and SS.
C. pH and temperature.
D. OFR and SLR.
3. The purpose of recycle for trickling filters is
A. to increase the mean cell detention time.
B. to decrease sludge wasting rates.
C. to increase hydraulic loading and dilute the influent BOD.
D. to increase surface area available to grow bacterial film.
4. Ozone is considered a secondary pollutant because
A. it is not a health risk
B. it causes damage to the upper atmosphere within seconds.
C. it can be produced in the biological treatment section of a sewage treatment plant.
D. it results from chemical reactions with certain primary pollutants.
5.
An inversion is an important condition for air pollution
A. in which warmer air above cooler air traps pollutants.
B. because it is extremely unstable.
C. in which cooler air in the upper atmosphere traps warmer air below.
D. because when it happens all pollutants have reversed health effects.
Flow Schematic (10 points). Draw a flow schematic for standard activated sludge secondary
wastewater treatment. Label all treatment units and chemical dose points and sludge production.
Clearly show all flow paths with lines and arrows.
CE 310 Sample Third Term Exam
Fall 20xx
Open Book/Notes Portion
B.A. DeVantier
Problem 2 (15 points) A room the size of the CE 310 classroom (20 ft x 20 ft x 10 ft) receives
CO2 at a rate of 40 g/hr due to student respiration. Treating the fresh outside air as the global
average 0.038 ppm CO2 concentration, calculate the steady CO2 concentration in the room (in
ppm at 25 C) if the refresh rate is 0.5 hr-1.
Problem 2 (15 points)
100x106 L/day
99.5x106 L/day
Act. Sludge
3000 mg/L
20x106 L
50x106 L/day
13 mg/L
500,000 L/day
9000 mg/L
9000 mg/L
For the activated sludge process diagram above, all concentrations shown are VSS (cell mass).
Find the hydraulic retention time in the activated sludge tank and the mean cell retention time.
Problem 3 (20 points) A 75 m tall smokestack generates NO2 at the rate of 40 kg/day into a
nearly isothermal atmosphere (1 K drop per km) and ambient temperature of 25 ºC, with a wind
speed of 1.95 m/s on a clear night. The stack exit diameter is 2 m, and the exit velocity is 10 m/s
at 95 ºC.
A. (10 of 20 points) Calculate the plume rise.
B. (10 of 20 points) What is the plume concentration 2 km directly downwind (y = 0) at an
altitude of 125 m in μg/m3? If you do not trust your plume rise result, assume what you
consider a reasonable height.