Multiple choice Flashcards
B
For domestic wastewater, gas production in a well operated anaerobic digester should be in the vicinity of:
A) 1 CU FT of gas per day per pound of volatile matter destroyed.
B) 10 BTU per pound of dry solids at 70% volatile
C) one cubic foot of gas per capita per day
D) 50 BTU per cubic foot
E) All of the above
C
The flow through rate for grit channel is usually: A) 20 seconds to 1.0 minute B) 2 feet per second C) 1 foot per second D) 30 days, depending on temperature E) none of the above
D
Under normal conditions, the maximum pounds of chlorine gas that can be drawn from a 150 lb. cylinder is: A) 10 lbs/day B) 20 lbs/day C) 30 lbs/day D) 40lbs/day E) 50 lbs/day
B
Grit usually contains some organic matter which decomposes and creates odors. To facilitate disposal without nuisance, the organic matter is removed by washing methods. Commonly used is: A) aeration B) elutriation C) vacuum filtration D) wet oxidation E) none of the above
D
Proportional weird usually are located at: A) a magnetic flow meter B) stilling wells C) aerobic digester scum boxes D) grit chambers E) water treatment plants
C
The main difference between primary and secondary clarifies is the: A) overall dimensions B) type of outlet weirs C) density of sludge D) detention period E) flow distribution
E
Which of the following characteristics would be least helpful to an operator assessing the organic loading on his plant? A) solids concentration. B) BOD C) COD D) pH E) nitrogen content
B
The destruction of the larger portion of microorganisms, with the probability that all pathogenic organisms are killed, is called: A) digestion B) disinfection C) dilution D) sterilization E) disposal
D
In the activated sludge treatment process, there are many control methods. One method is to maintain a constant BOD : MLVSS ratio. This is common my referred to as: A) MCRT B) SA C) SA : SDI D) F:M E) TS:SRT
B
The successful operation of an activated sludge plant requires the maintenance of proper solids concentration in the system. One major limiting factor is: A) mixed liquor tank volume B) effluent flow C) air supply D) chlorine demand E) none of the above
C
Overloading if a stabilization pond may occur with a subsequent loss of DO. One of the operation-oriented short-term corrective measures is:
A) addition of sodium nitrate
B) decreasing the recirculating
C) building scum rafts
D) increasing the efficient weir height
E) too high a DO in the wastewater being allies to the filter
E
If bearings on a centrifugal pump are running hot, checking for over lubrication or under lubrication would be listed as a general preventative maintenance service. If the lubrication is satisfactory the next preventative maintenance check would be: A) replace bearings B) operate only when needed C) clean the pump D) recheck TCH E) inspect alignment of pump and motor
B
One of the reasons that air should be excluded from anaerobic digesters is because:
A) gas storage capacity is reduced
B) the entrance of air mixed with the gas produced in the digester could create an explosive mixture
C) air interferes with the action of the aerobic bacteria present
D) harmful or pathogenic bacteria may be brought in with the air
E) none of the above
B
The volatile acid/alkalinity relationship of an anaerobic digester is an indication of the buffer capacity of the digester contents. When the ratio starts to increase, it indicates: A) excellent digester operation B) decreases in alkalinity C) better methane production D) a decrease in volatile acids E) an increase in pH
E
In an on-line treatment facility having three aerobic digesters in series, which of the following statements would be true?
A) it is not necessary to aerate all 3 digesters
B) draw off supernatant from tanks #2 and #3 only
C) a dissolved oxygen level will be easier to maintain in tank #3 than in tank #1
D) sludge pumped to digester #3 must be thicker than sludge pimped to digester# 2 and #2 thicker than #1
E) all of the above statements are true
A
The operation of a pond with a detention time of three days would provide treatment most comparable to: A) primary sedimentation. B) trickling filtration C) activated sludge D) sand filtration E) vacuum filtration
C
A two-stage trickling filtration system means:
A) one filter used with recirculating returning from filter effluent to filter influent at 100% of flow
B) one filter used with recirculation from secondary clarifier effluent to trickling filter influent.
C) two filters used in series, either directly or with a clarifier in between
D) two filters used in parallel
E) one filter used with no primary clarification.
D
Primary treatment units are designed to remove settleable solids from the wastewater stream by: A) biological treatment B) chemical addition C) biofiltration D) gravity sedimentation E) comminuting devices
B
Regardless of shape, one acre-foot of media in a trickling filter is equal to: A) 33,000 cu ft B) 43,560 cu ft C) 55,560 cu ft D) 77,840 cu ft E) none
D
The primary purpose of a secondary digester is to:
A) increase gas production
B) stabilize volatile solids
C) provide additional storage for detritus
D) allow for solids separation
C
Process unit efficiency can be determined by knowing:
A) loading and flow
B) length of unit
C) influent and effluent characteristics
D) pounds of solids removed
E) none of the above
C
Which of the following discharges would, in general, require the lowest chlorine dosage to ensure adequate disinfection? A) mixing B) contact time C) DO D) pH E) none of the above
A
Most circuit breakers are rated at what percentage of the motor amperage: A) 10% B) 25% C) 100% D) 125% E) none
B
If the packing on an operating centrifugal pump has a slight leakage, the following action should be taken: A) shut down immediately B) tighten packing gland C) lubricate pump packing gland D) decrease pump speed and head E) nothing
C
The laboratory test results on domestic raw sewage were:
COD = 320 mg/L BOD = 475 mg/L
The best interpretation would be:
A) the raw wastewater has a high grease content
B) the raw wastewater was septic
C) the laboratory results, as reported, were in error
D) the sample was held too long before analysis
E) the glass fiber filters used to run the test were containminated
C
Chlorination of wastewater effluents can: A) reduce BOD B) reAct with ammonia in water C) destroy pathogenic organisms D) react with nitrite ions E) all of the above
C
The SVI of activated sludge is defined as:
A) the volume of settled mixed liquor after 30 minutes of settling
B) the weight in grams of 200 ml of settled activated sludge
C) the volume in ml of 1 gram of activated sludge after 30 minutes of settling
D) the total volume of MLSS in the aeration tank
E) the volume of settled sludge in the secondary clairifiers
E
Which of the following would be included in the pretreatment unit? A) preaeration B) grit removal C) screening D) comminutor E) all of the above
