Basic Wastewater Operations- Chapter 12 (Disinfection) Exam Questions with Verified Answers
(Graded A+)
T/F: Disinfection prevents waterborne disease by protecting public water supplies, water for recreation,
and shellfish growing areas - Answers True
T/F: Waterborne diseases include typhoid, hepatitis A, cholera, dysentery, poliomyelitis, and measles. -
Answers False
T/F: Disinfection destroys disease-causing microorganisms called pathogens. - Answers True
T/F: Two methods often used to disinfect wastewater effluent are chlorination and ultra-purple
radiation. - Answers False; ultraviolet not ultra-purple
T/F: Chlorine is available in the pure gas and liquid state, granular or tablet form, and in water solutions.
- Answers True
T/F: Liquid chlorine is bleach. - Answers False
T/F: Chlorine gas is greenish-yellow in color, 2 1/2 times heavier than water, and has a strong pungent
odor. - Answers False; 2 1/2 times heavier than air
T/F: Chlorine does not burn, but is a strong oxidizer and reacts violently with oil and other hydrocarbons.
- Answers True
T/F: Calcium hypochlorite, known at HTH, contains 35% chlorine and 65% lime. - Answers False
T/F: Household bleach is 5.25% sodium hypochlorite dissolved in water. - Answers True
T/F: Dosage is the amount of chlorine applied; demand is the amount of chlorine used up; and residual is
the amount of chlorine left after demand. - Answers True
T/F: When chlorine and water mix, hypochlorous (HOCl) and hydrochloric (HCl) acid are formed. -
Answers True
T/F: Hypochlorous acid (HOCl), a powerful disinfectant, is the combined residual. - Answers False
T/F: When chlorine reacts with lime, chloramines form. - Answers False
T/F: Chloramines are the combined resisdual. - Answers True
Strong concentrations of chlorine can cause _______________.
A. Coughing
B. Vomiting
C. Suffocation
, D. All of the above - Answers D. All of the above
In case of exposure to chlorine, _______________.
A. Wash under a safety shower or with a garden hose
B. Flush eyes with cool water for 15 minutes
C. Get medical help
D. All of the above - Answers D. All of the above
Milk, coffee, or _____________ candy relieves throat irritation.
A. Chocolate
B. Licorice
C. Peppermint
D. Caramel - Answers C. Peppermint
Operators must use _______________ as a chlorine indicator in the titrimetric or spectrophotometric
residual test methods.
A. DDP
B. PPD
C. PDP
D. DPD - Answers D. DPD
Factos influencing disinfection are pH, temperature, contact time, chlorine concentration, and
_________________.
A. Water color
B. Residual type
C. Noise level
D. Air pollution - Answers B. Residual type
Because HOCl is a _________________, it is more effective at low pH.
A. Metal
B. Base
(Graded A+)
T/F: Disinfection prevents waterborne disease by protecting public water supplies, water for recreation,
and shellfish growing areas - Answers True
T/F: Waterborne diseases include typhoid, hepatitis A, cholera, dysentery, poliomyelitis, and measles. -
Answers False
T/F: Disinfection destroys disease-causing microorganisms called pathogens. - Answers True
T/F: Two methods often used to disinfect wastewater effluent are chlorination and ultra-purple
radiation. - Answers False; ultraviolet not ultra-purple
T/F: Chlorine is available in the pure gas and liquid state, granular or tablet form, and in water solutions.
- Answers True
T/F: Liquid chlorine is bleach. - Answers False
T/F: Chlorine gas is greenish-yellow in color, 2 1/2 times heavier than water, and has a strong pungent
odor. - Answers False; 2 1/2 times heavier than air
T/F: Chlorine does not burn, but is a strong oxidizer and reacts violently with oil and other hydrocarbons.
- Answers True
T/F: Calcium hypochlorite, known at HTH, contains 35% chlorine and 65% lime. - Answers False
T/F: Household bleach is 5.25% sodium hypochlorite dissolved in water. - Answers True
T/F: Dosage is the amount of chlorine applied; demand is the amount of chlorine used up; and residual is
the amount of chlorine left after demand. - Answers True
T/F: When chlorine and water mix, hypochlorous (HOCl) and hydrochloric (HCl) acid are formed. -
Answers True
T/F: Hypochlorous acid (HOCl), a powerful disinfectant, is the combined residual. - Answers False
T/F: When chlorine reacts with lime, chloramines form. - Answers False
T/F: Chloramines are the combined resisdual. - Answers True
Strong concentrations of chlorine can cause _______________.
A. Coughing
B. Vomiting
C. Suffocation
, D. All of the above - Answers D. All of the above
In case of exposure to chlorine, _______________.
A. Wash under a safety shower or with a garden hose
B. Flush eyes with cool water for 15 minutes
C. Get medical help
D. All of the above - Answers D. All of the above
Milk, coffee, or _____________ candy relieves throat irritation.
A. Chocolate
B. Licorice
C. Peppermint
D. Caramel - Answers C. Peppermint
Operators must use _______________ as a chlorine indicator in the titrimetric or spectrophotometric
residual test methods.
A. DDP
B. PPD
C. PDP
D. DPD - Answers D. DPD
Factos influencing disinfection are pH, temperature, contact time, chlorine concentration, and
_________________.
A. Water color
B. Residual type
C. Noise level
D. Air pollution - Answers B. Residual type
Because HOCl is a _________________, it is more effective at low pH.
A. Metal
B. Base
