(Part 1) Grade 4 wastewater certification practice
test with well researchrd questions and 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 - CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-negative 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 - CORRECT ANSWERS-c. 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) - CORRECT ANSWERS-d. 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 -
CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-c. 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 - CORRECT ANSWERS-d. 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 - CORRECT ANSWERS-b. 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 -
CORRECT ANSWERS-d. 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 - CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-b. 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 -
CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-c. 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 - CORRECT ANSWERS-d. 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 - CORRECT ANSWERS-b. 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 - CORRECT
ANSWERS-d. 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 - CORRECT ANSWERS-a. 2 hr
In an oxidation ditch, what would cause a dark gray color to develop in the mixed liquor?
test with well researchrd questions and 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 - CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-negative 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 - CORRECT ANSWERS-c. 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) - CORRECT ANSWERS-d. 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 -
CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-c. 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 - CORRECT ANSWERS-d. 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 - CORRECT ANSWERS-b. 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 -
CORRECT ANSWERS-d. 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 - CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-b. 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 -
CORRECT ANSWERS-b. 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 - CORRECT ANSWERS-c. 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 - CORRECT ANSWERS-d. 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 - CORRECT ANSWERS-b. 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 - CORRECT
ANSWERS-d. 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 - CORRECT ANSWERS-a. 2 hr
In an oxidation ditch, what would cause a dark gray color to develop in the mixed liquor?
