REHS Exam With Correct Questions
And Answers 2025
Which of the following organisms are most resistant to unfavorable
environmental conditions and indicate past of possibly intermittent pollution?
a. fecal streptococci
b. eschericha coli
c. aerobacter aerogenes
d. clostridium sporulates - CORRECT ANSWERS-clostridium sporulates
The presence of which of the following is most easily identified by laboratory
analysis in water contaminated by feces?
a. shigella dysenteriae
b. coliform
c. entamoeba histolytica
d. salmonella typhosa - CORRECT ANSWERS-coliform
Which of the following disinfecting compounds can be used in full strength for
disinfecting?
a. perchloron
b. calcium hypochlorite
c. chlorinated lime
d. sodium hypochlorite - CORRECT ANSWERS-sodium hypochlorite
This substance is the first product of the decomposition of organic matter. its
presence in water usually indicates "fresh pollution" of sanitary significance.
what is it?
a. ammonia
b. sugar
c. carbon dioxide
d. hydrogen sulfide - CORRECT ANSWERS-ammonia
The presence of which of the following elements in water treatment plant
effluent is used as a measure of filtration efficiency?
a. copper
b. aluminum
c. zinc
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,d. lead - CORRECT ANSWERS-aluminum
Which of the following is not used to disinfect water?
a. chlorine
b. bromine
c. fluorine
d. iodine - CORRECT ANSWERS-fluorine
The presence of which of the following in water would indicate past of possibly
intermittent pollution?
a. streptococcus fecalis
b. escherichia coli
c. clostridium perfringens
d. enterococci - CORRECT ANSWERS-clostridium perfringens
Often over 90% of sodium arsenate can be removed by
a. filtration
b. coagulation
c. ion exchange
d. all of the above - CORRECT ANSWERS-coagulation
Reduction of the level of fluorides in drinking water can be accomplished by
a. coagulation
b. lime softening
c. ion exchange
d. all of the above - CORRECT ANSWERS-all of the above
When collecting bacteriological samples that have been chlorinated, what
chemical is used to chlorinate the water?
a. sodium sulfate
b. sodium thiosulfate
c. sodium bisulfate
d. sodium bisulfite - CORRECT ANSWERS-sodium thiosulfate
Methylene blue active substance (MBAS) is a test to identify
a. hardness of water
b. iron in water
c. presence of detergents containing phosphates
2|Page
,d. presence of coliform in bacteria - CORRECT ANSWERS-presence of detergents
containing phosphates
Which organism is not known as an iron bacterium?
a. crenothrix
b. giardia lamblia
c. ferric chloride
d. leptothrix - CORRECT ANSWERS-giardia lamblia
The final product in biochemical oxidation of ammonia yields;
a. nitride
b. nitrite
c. nitrate
d. nitrogen - CORRECT ANSWERS-nitrate
Which contaminant in water is associated with methemoglobinemia?
a. zinc
b. lead
c. copper
d. nitrate - CORRECT ANSWERS-nitrate
The substance constantly used as a coagulant in water treatment is:
a. aluminum sulfate
b. calcium sulfate
c. potassium chloride
d. sodium phosphate - CORRECT ANSWERS-aluminum sulfate
The disinfecting ability of chlorine is affected most by:
a. BOD
b. temperature
c. hydrogen ion concentration
d. dissolved oxygen - CORRECT ANSWERS-hydrogen ion concentration
Alkalinity exists in three forms, which is not one of these forms?
a. bicarbonate
b. hydroxide
c. carbonate
d. hypochlorite - CORRECT ANSWERS-hypochlorite
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, Which of the following would not contribute to water hardness?
a. calcium sulfate
b. magnesium sulfate
c. calcium chloride
d. sodium chloride - CORRECT ANSWERS-sodium chloride
Improperly located wells, allowing fecal pollution of the water supply may lead
to outbreaks of:
a. botulism, leptospirosis, typhus fever, maria
b. brucellosis, strep infections, chlorea, yellow fever
c. salmonellosis, shigellosis, chlorea, hepatitis
d. relapsing fever, histoplasmosis, psittacosis - CORRECT ANSWERS-
salmonellosis, shigellosis, chlorea, hepatitis
Historically in the US, most of the impetus for adequate water treatment came
from the need to control:
a. infectious hepatitis
b. tuberculosis
c. malaria
d. typhoid - CORRECT ANSWERS-typhoid
The liquid form of chlorine used for emergency disinfection of small volumes of
a. calcium hypochlorite
b. sodium hypochlorite
c. bromide hypochlorite
d. potassium hypochlorite - CORRECT ANSWERS-sodium hypochlorite
The presumptive evidence of the presence of coliform in the MPN test is:
a. the color change in the culture media
b. turbidity of the culture broth
c. the presence of gas from the fermentation of the media
d. metallic sheen of colonies - CORRECT ANSWERS-the presence of gas from the
fermentation of the media
If hard water is softened by the ion exchange method, which one of the
following will increase?
a. dissolved oxygen
b. iron
c. p1-1
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And Answers 2025
Which of the following organisms are most resistant to unfavorable
environmental conditions and indicate past of possibly intermittent pollution?
a. fecal streptococci
b. eschericha coli
c. aerobacter aerogenes
d. clostridium sporulates - CORRECT ANSWERS-clostridium sporulates
The presence of which of the following is most easily identified by laboratory
analysis in water contaminated by feces?
a. shigella dysenteriae
b. coliform
c. entamoeba histolytica
d. salmonella typhosa - CORRECT ANSWERS-coliform
Which of the following disinfecting compounds can be used in full strength for
disinfecting?
a. perchloron
b. calcium hypochlorite
c. chlorinated lime
d. sodium hypochlorite - CORRECT ANSWERS-sodium hypochlorite
This substance is the first product of the decomposition of organic matter. its
presence in water usually indicates "fresh pollution" of sanitary significance.
what is it?
a. ammonia
b. sugar
c. carbon dioxide
d. hydrogen sulfide - CORRECT ANSWERS-ammonia
The presence of which of the following elements in water treatment plant
effluent is used as a measure of filtration efficiency?
a. copper
b. aluminum
c. zinc
1|Page
,d. lead - CORRECT ANSWERS-aluminum
Which of the following is not used to disinfect water?
a. chlorine
b. bromine
c. fluorine
d. iodine - CORRECT ANSWERS-fluorine
The presence of which of the following in water would indicate past of possibly
intermittent pollution?
a. streptococcus fecalis
b. escherichia coli
c. clostridium perfringens
d. enterococci - CORRECT ANSWERS-clostridium perfringens
Often over 90% of sodium arsenate can be removed by
a. filtration
b. coagulation
c. ion exchange
d. all of the above - CORRECT ANSWERS-coagulation
Reduction of the level of fluorides in drinking water can be accomplished by
a. coagulation
b. lime softening
c. ion exchange
d. all of the above - CORRECT ANSWERS-all of the above
When collecting bacteriological samples that have been chlorinated, what
chemical is used to chlorinate the water?
a. sodium sulfate
b. sodium thiosulfate
c. sodium bisulfate
d. sodium bisulfite - CORRECT ANSWERS-sodium thiosulfate
Methylene blue active substance (MBAS) is a test to identify
a. hardness of water
b. iron in water
c. presence of detergents containing phosphates
2|Page
,d. presence of coliform in bacteria - CORRECT ANSWERS-presence of detergents
containing phosphates
Which organism is not known as an iron bacterium?
a. crenothrix
b. giardia lamblia
c. ferric chloride
d. leptothrix - CORRECT ANSWERS-giardia lamblia
The final product in biochemical oxidation of ammonia yields;
a. nitride
b. nitrite
c. nitrate
d. nitrogen - CORRECT ANSWERS-nitrate
Which contaminant in water is associated with methemoglobinemia?
a. zinc
b. lead
c. copper
d. nitrate - CORRECT ANSWERS-nitrate
The substance constantly used as a coagulant in water treatment is:
a. aluminum sulfate
b. calcium sulfate
c. potassium chloride
d. sodium phosphate - CORRECT ANSWERS-aluminum sulfate
The disinfecting ability of chlorine is affected most by:
a. BOD
b. temperature
c. hydrogen ion concentration
d. dissolved oxygen - CORRECT ANSWERS-hydrogen ion concentration
Alkalinity exists in three forms, which is not one of these forms?
a. bicarbonate
b. hydroxide
c. carbonate
d. hypochlorite - CORRECT ANSWERS-hypochlorite
3|Page
, Which of the following would not contribute to water hardness?
a. calcium sulfate
b. magnesium sulfate
c. calcium chloride
d. sodium chloride - CORRECT ANSWERS-sodium chloride
Improperly located wells, allowing fecal pollution of the water supply may lead
to outbreaks of:
a. botulism, leptospirosis, typhus fever, maria
b. brucellosis, strep infections, chlorea, yellow fever
c. salmonellosis, shigellosis, chlorea, hepatitis
d. relapsing fever, histoplasmosis, psittacosis - CORRECT ANSWERS-
salmonellosis, shigellosis, chlorea, hepatitis
Historically in the US, most of the impetus for adequate water treatment came
from the need to control:
a. infectious hepatitis
b. tuberculosis
c. malaria
d. typhoid - CORRECT ANSWERS-typhoid
The liquid form of chlorine used for emergency disinfection of small volumes of
a. calcium hypochlorite
b. sodium hypochlorite
c. bromide hypochlorite
d. potassium hypochlorite - CORRECT ANSWERS-sodium hypochlorite
The presumptive evidence of the presence of coliform in the MPN test is:
a. the color change in the culture media
b. turbidity of the culture broth
c. the presence of gas from the fermentation of the media
d. metallic sheen of colonies - CORRECT ANSWERS-the presence of gas from the
fermentation of the media
If hard water is softened by the ion exchange method, which one of the
following will increase?
a. dissolved oxygen
b. iron
c. p1-1
4|Page
