WATER OPERATOR CERTIFICATION STUDY MATERIAL
( NEW MEXICO) (BASIC) EXAM 2025 QUESTIONS
AND ANSWERS
Two of the most important factors impacting the effectiveness of chlorination
are? - (ANSWER)Concentration of the chlorine and contact time
The treatment process that controls corrosion or scaling is known as? -
(ANSWER)Stabilization
Permanganate reactions are highly dependent upon? - (ANSWER)pH
It is hardest to kill the organism that causes which one of the following illnesses
A. Cholera
B. Typhoid
C. Cryptosporidiosis
D. Infectious hepatitis - (ANSWER)C. Cryptosporidiosis
Disinfection of water wells with free chlorine requires exposure for how many
hours at what concentration? - (ANSWER)12 to 24 hours at 50 mg/L
Which index determines the calcium carbonate deposition property of water by
calculating the saturation pH, where a negative value indicates corrosive water
and a positive value indicates depositing water? - (ANSWER)Langelier saturation
index
,The advantage to using the oxidant ozone is? - (ANSWER)It has little pH effect
Pretreatment with chlorine is being eliminated at many water treatment plants
because it has been shown to? - (ANSWER)Sometimes produce disinfection by
products known to be carcinogenic
CTs are based on? - (ANSWER)Concentration of chlorine, contact time, pH, and
temperature
If the natural flouride content of the raw water is variable, the concentration of
the raw water should be measure how often? - (ANSWER)Every day
What is the primary drawback for facilities that use ultraviolet light to disinfect
water? - (ANSWER)There is potential for the light bulbs to be coated with light
obscuring material preventing the UV light from killing microorganisms
Potassium permanganate is most effective in? - (ANSWER)Removing iron
Chlorine is advantageous over chloramines because? - (ANSWER)Chlorine is a
much stronger oxidant
Which oxidant has the potential of producing ClO₃ byproducts? -
(ANSWER)Chlorine dioxide
,How thick should the layer of sodium flouride crystals be maintained in a
saturator tank for flows of less than 100 gpm? - (ANSWER)6 inches
Which disinfectant would work best against Cryptosporidium? - (ANSWER)Ozone
Which chemical oxidant would be best to use for controlling trihalomethanes
formation potential?
A. Chloramines
B. Chlorine dioxide
C. Oxygen
D. Potassium permanganate - (ANSWER)D. Potassium permanganate
Ozone generators
A. Must be supplied with extremely dry air
B. Are usually plate type generators for large plants
C. Will produce 12% ozone by weight when supplied with air
D. Will produce about 20% ozone by weight when supplied with oxygen only -
(ANSWER)A. Must be supplied with extremely dry air
If air is used to generate ozone, which percentage of the air is usually converted
to ozone? - (ANSWER)1% to 3%
, Detention time in flocculation basins are usually designed to provide for how
many minutes? - (ANSWER)15 to 45 minutes
Alum works best in a pH range of? - (ANSWER)5.8 to 7.0
Which statement concerning colloidal particles is true?
A. They are so small gravity has little effect on them
B. The zeta potential between colloidal particles is balanced by covalent bonding
C. Electrical phenomenon of colloidal particles predominate and control their
behavior
D. The surface area of colloidal particles is very small compared to their mass -
(ANSWER)A. Colloidal particles are so small that gravity has little effect on them
Which natural electrical force keeps colloidal particles apart in water treatment? -
(ANSWER)Zeta potential
The zeta potential measures what? - (ANSWER)The number of excess electrons
found on the surface of all particulate matter
Low temperature water can be compensated for when using alum by? -
(ANSWER)Increasing the alum dose
What is the optimal pH range for the removal of particulate matter, when using
alum as a coagulant? - (ANSWER)6.5 to 7.2
( NEW MEXICO) (BASIC) EXAM 2025 QUESTIONS
AND ANSWERS
Two of the most important factors impacting the effectiveness of chlorination
are? - (ANSWER)Concentration of the chlorine and contact time
The treatment process that controls corrosion or scaling is known as? -
(ANSWER)Stabilization
Permanganate reactions are highly dependent upon? - (ANSWER)pH
It is hardest to kill the organism that causes which one of the following illnesses
A. Cholera
B. Typhoid
C. Cryptosporidiosis
D. Infectious hepatitis - (ANSWER)C. Cryptosporidiosis
Disinfection of water wells with free chlorine requires exposure for how many
hours at what concentration? - (ANSWER)12 to 24 hours at 50 mg/L
Which index determines the calcium carbonate deposition property of water by
calculating the saturation pH, where a negative value indicates corrosive water
and a positive value indicates depositing water? - (ANSWER)Langelier saturation
index
,The advantage to using the oxidant ozone is? - (ANSWER)It has little pH effect
Pretreatment with chlorine is being eliminated at many water treatment plants
because it has been shown to? - (ANSWER)Sometimes produce disinfection by
products known to be carcinogenic
CTs are based on? - (ANSWER)Concentration of chlorine, contact time, pH, and
temperature
If the natural flouride content of the raw water is variable, the concentration of
the raw water should be measure how often? - (ANSWER)Every day
What is the primary drawback for facilities that use ultraviolet light to disinfect
water? - (ANSWER)There is potential for the light bulbs to be coated with light
obscuring material preventing the UV light from killing microorganisms
Potassium permanganate is most effective in? - (ANSWER)Removing iron
Chlorine is advantageous over chloramines because? - (ANSWER)Chlorine is a
much stronger oxidant
Which oxidant has the potential of producing ClO₃ byproducts? -
(ANSWER)Chlorine dioxide
,How thick should the layer of sodium flouride crystals be maintained in a
saturator tank for flows of less than 100 gpm? - (ANSWER)6 inches
Which disinfectant would work best against Cryptosporidium? - (ANSWER)Ozone
Which chemical oxidant would be best to use for controlling trihalomethanes
formation potential?
A. Chloramines
B. Chlorine dioxide
C. Oxygen
D. Potassium permanganate - (ANSWER)D. Potassium permanganate
Ozone generators
A. Must be supplied with extremely dry air
B. Are usually plate type generators for large plants
C. Will produce 12% ozone by weight when supplied with air
D. Will produce about 20% ozone by weight when supplied with oxygen only -
(ANSWER)A. Must be supplied with extremely dry air
If air is used to generate ozone, which percentage of the air is usually converted
to ozone? - (ANSWER)1% to 3%
, Detention time in flocculation basins are usually designed to provide for how
many minutes? - (ANSWER)15 to 45 minutes
Alum works best in a pH range of? - (ANSWER)5.8 to 7.0
Which statement concerning colloidal particles is true?
A. They are so small gravity has little effect on them
B. The zeta potential between colloidal particles is balanced by covalent bonding
C. Electrical phenomenon of colloidal particles predominate and control their
behavior
D. The surface area of colloidal particles is very small compared to their mass -
(ANSWER)A. Colloidal particles are so small that gravity has little effect on them
Which natural electrical force keeps colloidal particles apart in water treatment? -
(ANSWER)Zeta potential
The zeta potential measures what? - (ANSWER)The number of excess electrons
found on the surface of all particulate matter
Low temperature water can be compensated for when using alum by? -
(ANSWER)Increasing the alum dose
What is the optimal pH range for the removal of particulate matter, when using
alum as a coagulant? - (ANSWER)6.5 to 7.2
