Test # 2 for Wastewater Treatment Plant Operators...
Information...
The Grade II examination contains questions regarding the following subjects : basic safety practices, hazards encountered
during wastewater treatment plant operations, sampling and simple analysis of wastewater constituents, operation and
maintenance procedures in preliminary and primary treatment unit processes, anaerobic sludge digestion and disinfection.
It also includes specific questions on the operation and maintenance of wastewater stabilization ponds and state
regulations regarding the classification of wastewater treatment plants and operator certification. In addition, the
Grade II examination includes questions on secondary unit processes (e.g. trickling filters, activated sludge), sludge
handling, evaluation of wastewater unit processes as well as overall plant performance and basic supervision
responsibilities.
The Grade II examination also contains mathematical questions. Examinees may be asked to calculate a variety of problems
including hydraulic or organic loading rate, SVI index, removal efficiency (% removal), activated sludge F/M ratio,
activated sludge MCRT, pumping rate, sludge pumping rate, detention time, chlorine residual/demand, flow velocity,
volume or surface area, overflow rate and nitrification. The examinee should be familiar with typical calculations
related to the subject matter listed in paragraph 1.
6 True/False Questions
1 Point Each
4 Multiple Choice Questions
2 Points Each
5 Math Problems
4 Points Each
Total Points : 34
True / False Questions...
1. The F in the F to M ratio refers to the pounds of mixed liquor volatile suspended solids under aeration in an
activated sludge plant.
2. Digester gas containing 60% methane by volume will likely explode when exposed to a spark or flame.
3. The units ppm and % are considered roughly equivalent for wastewater treatment calculations.
4. The velocity of wastewater flowing through a long channel type of grit chamber may be controlled by a proportional weir.
5. High amounts of hydrogen sulfide gas in a moist atmosphere can result in corrosion of concrete structures.
6. The trickling filter recirculation ratio is calculated as follows : Q / QR
(where Q : wastewater flowrate and QR : recirculated flowrate)
Multiple Choice Questions...
7. The measure of the effectiveness of chlorine in disinfection is :
a. The chlorine demand.
b. The chlorine dosage.
c. The chlorine residual.
d. The amount of chloramine formed.
e. The final effluent coliform concentration.
8. Carry over of grit from the grit chamber may indicate the need to :
a. Clean the chamber more frequently.
b. Decrease the operational depth of the channel.
c. Increase the flow to the primary clarifier.
d. Change the cycle of sludge removal.
e. Increase the air input to an aerated grit chamber.
9. The expected range of BOD removal in a well operated primary clarifier is :
a. 10 to 20%
b. 20 to 40%
c. 40 to 60%
d. 60 to 80%
e. Over 80%
10. Which one of the following process units is usually classified as a sludge thickening device as opposed to a
dewatering device :
a. DAF unit.
b. Sludge drying bed.
c. Vacuum filter press.
d. Belt press.
e. All of the above are thickeners, not dewatering devices.
Math Questions...
11. A trickling filter wastewater treatment plant receives a flow 1.95 MGD. Calculate the organic loading to this plant
if it has a 135 ft diameter trickling filter with a 5 foot media depth and has a primary effluent BOD concentration of
110 mg/L.
a. 0.5 lbs BOD/1,000 ft³/day.
b. 2.7 lbs BOD/1,000 ft³/day.
c. 25 lbs BOD/1,000 ft³/day.
d. 39 lbs BOD/1,000 ft³/day.
e. 44 lbs BOD/1,000 ft³/day.
12. At a wastewater treatment plant which receives a flow rate of 650,000 gallons per day, a total of 50 cubic feet of
grit was removed for the month. Calculate the rate of grit removal assuming 30 days in a month.
a. 1.1 cu.ft./MG.
b. 1.3 cu.ft./MG.
c. 1.7 cu.ft./MG.
d. 2.0 cu.ft./MG.
e. 2.6 cu.ft./MG.
13. At an activated sludge wastewater treatment plant receiving 3.25 MGD, the final effluent suspended solids
concentration averages 21.2 mg/L. What would the calculated MCRT value be when the aeration basin carries 2,050 mg/L
MLSS and wastes 0.0550 MGD. The waste activated sludge has a concentration of 7,980 mg/L. The aeration tank has a
volume of 1.00 MG and the secondary clarifier has an operational volume of 0.250 MG.
a. 2.5 days
b. 5.0 days
c. 7.5 days
d. 15 days
e. 42 days
14. At a 5.32 MGD wastewater treatment plant the final effluent is determined to have a suspended solids concentration
of 23.5 mg/L. How many pounds of suspended solids are being discharged daily ?
a. 1043 lbs/day
b. 935 lbs/day
c. 125 lbs/day
d. 37 lbs/day
e. 15 lbs/day
15. It is found that at a wastewater treatment pond system 35 days are required to bring the pond system to its operations
depth of 3.5 feet. Assuming that the pond system was empty when the filling of the pond was initiated and that a constant
incoming flow rate fills the pond, what would be the hydraulic loading on this pond system ?
a. 0.47 inches/day
b. 1.2 inches/day
c. 2.1 inches/day
d. 3.5 inches/day
e. 10.0 inches/day
