(Part 1) Grade 4 wastewater certification practice test Questions with Correct Answers

What is the odor detection limit of chlorine gas? a. 0.1 ppm b. 0.3 ppm c. 0.5 ppm d. 1.0 ppm - ANSWERSb. 0.3 ppm What is a cathode? a. negative pole of an electrolyte b. positive pole of an electrolyte c. negative pole of an electrolytic cell or system d. positive pole of an electrolytic cell or system - ANSWERSnegative pole of an electrolytic cell or system The least reactive metals are called a. anodic metals b. galvanic metals c. cathodic metals d. tempered metals - ANSWERSc. cathodic metals Unless water cooled, the operating temperature of a mechanical seal in a pump should never exceed a. 95°F (35°C) b. 120°F (49°C) c. 140°F (60°C) d. 160°F (71°C) - ANSWERSd. 160°F (71°C) What term describes the condition that exists when the source of the water supply is below the centerline of the pump? a. total discharge head b. suction lift c. velocity head d. pressure head - ANSWERSb. suction lift All occupied trenches 4 or more ft deep must provide exits at a. 15-ft intervals b. 20-ft intervals c. 25-ft intervals d. 30-ft intervals - ANSWERSc. 25-ft intervals What is the difference between a weak acid and a strong acid? a. amount of buffering released b. amount of hydroxyl ions released c. amount of carbonate ions released d. amount of hydrogen ions released - ANSWERSd. amount of hydrogen ions released Which one of the following is the best type of valve to use to dampen a water hammer? a. needle b. pressure-relief c. pressure-reducing d. pinch - ANSWERSb. pressure-relief A shock load of toxic wastes coming into a plant can be treated or controlled with a. coagulants only b. coagulants and lime c. coagulants and coagulant aid d. coagulants or chlorine - ANSWERSd. coagulants or chlorine Toxic solids should be disposed of in a. a digester to destabilize and break down the toxins b. an approved sanitary landfill c. an incinerator d. a sludge pond for further aerobic breakdown - ANSWERSb. an approved sanitary landfill Which one of the following best defines the term stray-current corrosion? a. decomposition of a metal by its reaction with an acidic water b. decomposition of a material caused by an outside electric current c. reaction between a metal and water d. reaction between two different metals with water acting as an electrolyte - ANSWERSb. decomposition of a material caused by an outside electric current On startup of a small package wastewater treatment plant, lime should be added to the digestion unit when the pH goes below a. 6.8 b. 7.0 c. 7.2 d. 7.5 - ANSWERSb. 7.0 If the effluent to a small package wastewater treatment plant using the activated sludge process appears turbid, what is most probably the cause? a. low concentration of dissolved oxygen (DO) in the aeration tank b. pumping rate for the return of activated sludge is out of balance c. excessive aeration rates in the aeration tank d. alkalinity is too high - ANSWERSb. pumping rate for the return of activated sludge is out of balance If a small package treatment plant utilizing the activated sludge process has a lightcolored floating sludge on the surface of the clarifier, which one of the following would most likely eliminate the floating sludge? a. increase the sludge wasting rate b. add a pH stabilizer, as pH is too low c. reduce the aeration rates d. increase the return sludge rate - ANSWERSc. reduce the aeration rates What usually causes frothing in the activated sludge process? a. too low a solids level b. too high a solids leaving c. too short a retention time d. too long a detention time - ANSWERSd. too long a detention time Which one of the following suggestions would most likely control foaming? a. increase the detention time b. water sprays c. increase the dissolved oxygen d. increase solids wasting - ANSWERSb. water sprays What is the ideal level of solids in a jar test sample collected from an aeration tank if it is allowed to settle for 30 min? a. ¼ of the jar depth b. ⅓ of the jar depth c. ⅖ of the jar depth d. ½ of the jar depth - ANSWERSd. ½ of the jar depth In a small wastewater treatment plant using the activated sludge process, solids in the settling compartment should not be allowed to remain longer than a. 2 hr b. 3 hr c. 4 hr d. 5 hr - ANSWERSa. 2 hr In an oxidation ditch, what would cause a dark gray color to develop in the mixed liquor? a. the buildup of facultative bacteria b. the buildup of aerobic bacteria c. the buildup of anaerobic bacteria d. the lack of bacteria buildup - ANSWERSd. the lack of bacteria buildup During the startup of the oxidation sludge process in the oxidation ditch, the operator should maintain the highest a. recommended level of dissolved oxygen b. inflow of raw wastewater possible in order to fill the ditch c. possible rate of returned activated sludge d. possible brush rotor speed advisable - ANSWERSc. possible rate of returned activated sludge What is the best range of dissolved oxygen in an oxidation ditch for optimum operation? a. 0.5 to 2.0 mg/L b. 1.0 to 2.0 mg/L c. 1.0 to 2.5 mg/L d. 1.0 to 3.0 mg/L - ANSWERSa. 0.5 to 2.0 mg/L Overoxidation of an oxidation ditch will cause a. an algae bloom b. suspended solids to float c. oxygen toxicity for protozoans and other organisms, especially rotifers d. the formation of pinpoint floc - ANSWERSd. the formation of pinpoint floc In the oxidation ditch process, what should be done if dark solids appear in the settling tank? a. increase disinfection to reduce septic conditions and waste b. increase the return sludge rate c. add oxygen to the settling tank through the clarifier's diffusers d. waste all the solids and start the settling process over - ANSWERSb. increase the return sludge rate A thick dark foam on the surface of the oxidation ditch indicates that the a. process is performing well b. rotor revolutions per minute (rpm) are too fast c. wasting rate should be increased d. flow through the ditch is too slow - ANSWERSc. wasting rate should be increased What should the operator do if the oxidation ditch becomes hydraulically overloaded due to a heavy rainstorm? a. temporarily store the excess rainwater in the primary clarifier b. increase the dissolved oxygen levels c. shut down one or more rotor assemblies d. send excess wastewater to the settling tank - ANSWERSc. shut down one or more rotor assemblies