(PART 1) GRADE 4 WASTEWATER CERTIFICATION PRACTICE TEST QUESTIONS AND ANSWERS WITH SOLUTIONS 2024

(PART 1) GRADE 4 WASTEWATER
CERTIFICATION PRACTICE TEST
QUESTIONS AND ANSWERS WITH
SOLUTIONS 2024
What is the odor detection limit of chlorine gas?
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a. 0.1 ppm b. 0.3 ppm c. 0.5 ppm d. 1.0 ppm - ANSWER b. 0.3 ppm
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What is a cathode? N N N




a. negative pole of an electrolyte b. positive pole of an electrolyte c. negative pole of an electrolytic cell
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or system d. positive pole of an electrolytic cell or system -
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ANSWER negative pole of an electrolytic cell or system
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The least reactive metals are called a. anodic metals b. galvanic metals c. cathodic metals d. tempered m
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etals - ANSWER c. cathodic metals
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Unless water cooled, the operating temperature of a mechanical seal in a pump should never exceed a.
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95°F (35°C) b. 120°F (49°C) c. 140°F (60°C) d. 160°F (71°C) - ANSWER d. 160°F (71°C)
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What term describes the condition that exists when the source of the water supply is below the centerli
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ne of the pump? a. total discharge head b. suction lift c. velocity head d. pressure head -
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ANSWER b. suction lift
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All occupied trenches 4 or more ft deep must provide exits at a. 15-ft intervals b. 20-ft intervals c. 25-
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ft intervals d. 30-ft intervals - ANSWER c. 25-ft intervals
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What is the difference between a weak acid and a strong acid? a. amount of buffering released b. amou
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nt of hydroxyl ions released c. amount of carbonate ions released d. amount of hydrogen ions released -
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ANSWER d. amount of hydrogen ions released
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Which one of the following is the best type of valve to use to dampen a water hammer? a. needle b. pre
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ssure-relief c. pressure-reducing d. pinch - ANSWER b. pressure-relief
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,A shock load of toxic wastes coming into a plant can be treated or controlled with
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a. coagulants only b. coagulants and lime c. coagulants and coagulant aid d. coagulants or chlorine -
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ANSWER d. coagulants or chlorine
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Toxic solids should be disposed of in
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a. a digester to destabilize and break down the toxins b. an approved sanitary landfill c. an incinerator d.
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a sludge pond for further aerobic breakdown - ANSWER b. an approved sanitary landfill
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Which one of the following best defines the term stray-current corrosion?
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a. decomposition of a metal by its reaction with an acidic water b. decomposition of a material caused b
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y an outside electric current c. reaction between a metal and water d. reaction between two different m
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etals with water acting as an electrolyte -
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NANSWER b. decomposition of a material caused by an outside electric current
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On startup of a small package wastewater treatment plant, lime should be added to the digestion unit w
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hen the pH goes below
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a. 6.8 b. 7.0 c. 7.2 d. 7.5 - ANSWER b. 7.0
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If the effluent to a small package wastewater treatment plant using the activated sludge process appears
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Nturbid, what is most probably the cause?
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a. low concentration of dissolved oxygen (DO) in the aeration tank b. pumping rate for the return of activ
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ated sludge is out of balance c. excessive aeration rates in the aeration tank d. alkalinity is too high -
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ANSWER b. pumping rate for the return of activated sludge is out of balance
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If a small package treatment plant utilizing the activated sludge process has a lightcolored floating sludg
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e on the surface of the clarifier, which one of the following would most likely eliminate the floating sludg
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e?
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, a. increase the sludge wasting rate b. add a pH stabilizer, as pH is too low c. reduce the aeration rates d. i
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ncrease the return sludge rate - ANSWER c. reduce the aeration rates
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What usually causes frothing in the activated sludge process?
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Na. too low a solids level b. too high a solids leaving c. too short a retention time d. too long a detention t
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ime - ANSWER d. too long a detention time
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Which one of the following suggestions would most likely control foaming?
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a. increase the detention time b. water sprays c. increase the dissolved oxygen d. increase solids wasting
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- ANSWER b. water sprays
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What is the ideal level of solids in a jar test sample collected from an aeration tank if it is allowed to settl
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e for 30 min?
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a. ¼ of the jar depth b. ⅓ of the jar depth c. ⅖ of the jar depth d. ½ of the jar depth -
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ANSWER d. ½ of the jar depth
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In a small wastewater treatment plant using the activated sludge process, solids in the settling compart
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ment should not be allowed to remain longer than
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a. 2 hr b. 3 hr c. 4 hr d. 5 hr - ANSWER a. 2 hr
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In an oxidation ditch, what would cause a dark gray color to develop in the mixed liquor?
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a. the buildup of facultative bacteria b. the buildup of aerobic bacteria c. the buildup of anaerobic bacter
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ia d. the lack of bacteria buildup - ANSWER d. the lack of bacteria buildup
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During the startup of the oxidation sludge process in the oxidation ditch, the operator should maintain t
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he highest N N