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 - ANSWER 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 - ANSWER neg-
ative 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 - ANSWER 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) - ANSWER 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 - ANSWER b. suction lift
All occupied trenches 4 or more ft deep must provide exits at a. 15-ft intervals b. 20-ft inter-
vals c. 25-ft intervals d. 30-ft intervals - ANSWER c. 25-ft intervals
What is the difference between a weak acid and a strong acid? a. amount of buffering re-
leased b. amount of hydroxyl ions released c. amount of carbonate ions released d. amount
of hydrogen ions released - ANSWER d. amount of hydrogen ions released
1
,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 - ANSWER 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 - ANSWER 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 - ANSWER 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 mate-
rial 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 - ANSWER b. decompo-
sition of a material caused by an outside electric current
On startup of a small package wastewater treatment plant, lime should be added to the di-
gestion unit when the pH goes below
a. 6.8 b. 7.0 c. 7.2 d. 7.5 - ANSWER b. 7.0
If the effluent to a small package wastewater treatment plant using the activated sludge pro-
cess 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.
2
, alkalinity is too high - ANSWER 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 aera-
tion rates d. increase the return sludge rate - ANSWER 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 - ANSWER 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 - ANSWER b. water sprays
What is the ideal level of solids in a jar test sample collected from an aeration tank if it is al-
lowed 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 - AN-
SWER d. ½ of the jar depth
In a small wastewater treatment plant using the activated sludge process, solids in the set-
tling compartment should not be allowed to remain longer than
a. 2 hr b. 3 hr c. 4 hr d. 5 hr - ANSWER a. 2 hr
3
a. 0.1 ppm b. 0.3 ppm c. 0.5 ppm d. 1.0 ppm - ANSWER 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 - ANSWER neg-
ative 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 - ANSWER 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) - ANSWER 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 - ANSWER b. suction lift
All occupied trenches 4 or more ft deep must provide exits at a. 15-ft intervals b. 20-ft inter-
vals c. 25-ft intervals d. 30-ft intervals - ANSWER c. 25-ft intervals
What is the difference between a weak acid and a strong acid? a. amount of buffering re-
leased b. amount of hydroxyl ions released c. amount of carbonate ions released d. amount
of hydrogen ions released - ANSWER d. amount of hydrogen ions released
1
,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 - ANSWER 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 - ANSWER 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 - ANSWER 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 mate-
rial 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 - ANSWER b. decompo-
sition of a material caused by an outside electric current
On startup of a small package wastewater treatment plant, lime should be added to the di-
gestion unit when the pH goes below
a. 6.8 b. 7.0 c. 7.2 d. 7.5 - ANSWER b. 7.0
If the effluent to a small package wastewater treatment plant using the activated sludge pro-
cess 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.
2
, alkalinity is too high - ANSWER 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 aera-
tion rates d. increase the return sludge rate - ANSWER 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 - ANSWER 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 - ANSWER b. water sprays
What is the ideal level of solids in a jar test sample collected from an aeration tank if it is al-
lowed 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 - AN-
SWER d. ½ of the jar depth
In a small wastewater treatment plant using the activated sludge process, solids in the set-
tling compartment should not be allowed to remain longer than
a. 2 hr b. 3 hr c. 4 hr d. 5 hr - ANSWER a. 2 hr
3
