WT MC
Which of the following is not a commonly-used coagulant?
Cationic polymer
Ferric sulfate
Alum
Sulfuric acid
Which of the following is not a process that will remove pathogens from water?
Filtration
Sedimentation
Screening
Disinfection
If turbidity is rising rapidly, what should you do?
Test for soluble iron concentration
Check the sodium hypochlorite pumping rate
Investigate the cause of hardness
Verify the effectiveness of the coagulant chemicals and dosage at the flash mixer
Which of the following is not a mechanism that occurs in a filter media?
Straining
Adsorption
Sedimentation on media
Precipitation
Which of the following is not a type of filter media used for gravity filtration?
Diatomaceous earth
Mixed media
Dual media
Single media
What does the term "fluidized" mean in filtration?
The media is in need of a backwash
Filter media is expanded during backwash
The media has been soaked in water after installation
The media needs to be replaced due to old age
How is the filtration efficiency evaluated?
Number of surface wash
Loss of media
Turbidity measurement
Depth of media
When is a hypochlorinator typically used?
To inject chlorine gas
To feed liquid chlorine
To measure the concentration of chlorine
To dechlorinate water
What is the purpose of filtration?
To settle out larger suspended particles
To control corrosion
To gather together fine, light particles to form larger particles (floc) to aid the sedimentation and filtration processes
None of these
What is the disadvantage of using ozone to disinfect water?
Oxidation of iron and manganese
Effectiveness in destroying virus and bacteria
Contact time
Cost
What type of charge would you expect to see on a coagulant?
Neutral
Negative
Positive
Anionic
What are common filtration rates in gravity filtration?
0.1 to 1.9 gpm/sq. ft
2 to 10 gpm/sq. ft
11 to 20 gpm/sq. ft
21 to 28 gpm/sq. ft
What is the purpose of the coagulation and flocculation process?
To strain and adsorb the solids
Maintain a negative charge on the colloids
To remove solids using gravity
Neutralize the negative charges on the colloids, and slowly stir water to create flocs
When the filter media gets clogged due to deposit of solids, the pressure loss in the filter:
Is not affected
Is increased
Becomes irrelevant
Is decreased
What is an attribute of a diatomaceous earth filter?
Mesh screen is pre-coated with powdered media
Involves special pore-sized membranes that separates microorganisms and suspended particles from water
Contains manganese greensand
Applicable for high turbidity water
Which of the following is equal to 100 mg/L?
1 ppm
100 ppm
10 mg/L
1,000 mg/L
Which of the following would not trigger a filtration system to backwash?
PH
Headloss
Turbidity
Time
Which of the followings is an important part of a hypochlorinator?
A diaphragm pump
A solution tank
Check valve
All of these
When chlorinating water, the operator knows that the residual is beyond the breakpoint chlorination if:
There is free residual
Total residual is zero
There is no free residual
All residual is combined
Which acid is formed when chlorine is mixed with water?
Humic acid
Hypochlorous acid
Hydrobromic acid
Fulvic acid
The function of a flocculation basin is to
Allow suspended particles to grow
Mix chemicals
Settle colloidal particles
Destabilize colloidal particles
What causes the water to look cloudy?
Alkalinity
Hardness
Dissolved solids
None of these
Sedimentation produces waste known as
Mud
Sludge
Wastewater
Backwash water
Important processes which occur during filtration are
Sedimentation
Adsorption
Straining
All of the Above
What is the accepted method used to measure turbidity?
Jackson
Candle
Nephelometric
Light
What is the disadvantage of using UV to disinfect water?
Weak disinfectant
Unstable
Formation of TTHMs
No disinfectant residual
The form of chlorine which is 100% available chlorine is
Gaseous Chlorine
Sodium Hypochlorite
Calcium Hydroxide
Calcium Hypochlorite
What is typically used to clean the sludge on the bottom of a rectangular clarifier?
Eductor
Baffles
Chain and flight collectors
Weir
If the chlorine demand in the water is 1.5 mg/L and the amount of chlorine dose is 3.5 ppm, what is the chlorine residual?
1.5 mg/L
3.5 mg/L
2.0 mg/L
5.0 mg/L
When chlorine reacts with natural organic matter in water it can create
Coliform bacteria
Calcium
Disinfectant by-products
Chloroform
What is the purpose of pre-chlorination?
To control taste and odor
To address hardness
Corrosion Control
To address lead and copper problem
The optimal coagulant dose is determined by a
Chlorine Test
Coagulation test
Jar Test
Flocculation test
What are colloidal particles?
Large sized particles
Gravel
Non-settleble smaller sized particles, such as bacteria and fine clays
Settleable solids
What would cause excessive media to be in the spent backwash water?
Backwashing at high velocity
Headloss in the media
Mudball formation
Surface washing equipment has malfunctioned
Why should the water treatment plant operator be present during both the design and construction periods of a project to improve a water treatment plant?
To check on the engineer's treatment process calculations
To be completely familiar with the entire plant layout, including the piping, equipment, and machinery and their intended operation
To make sure the lowest contractor's bid is accepted
To ensure that all electrical monitoring instrumentation is properly wired
An empty water storage tank is 6 ft in diameter and 30 ft high. How many hours will it take to completely fill it up, if the well is pumping at 24 gpm into the tank?
19 hours
7.3 hours
2.2 hours
4.4 hours
A direct filtration plant operates 3 dual-media filters, each measuring 23 ft by 36 ft for a 24 hour period. The filters operate at a design filtration rate of 4.6 gpm/ft2. Calculate the daily production of the plant in MGD.
26.5 MGD
46.5 MGD
100 MGD
16.5 MGD
Calculate the velocity of water in fps, if water is flowing at 19 cuft/sec through a 36-inch water main 3,000 feet long.
4.5 fps
2.7 fps
7.1 fps
12.3 fps
A 3.0-ft diameter pipe that is 1,876 ft long was disinfected with chlorine. If 41.33 lbs of chlorine were used, what was the dosage in milligram per liter?
41 mg/L
50 mg/L
13 mg/L
99 mg/L
A water supply has a flow of 750,000 gal/day. If sodium hypochlorite with 10% available chlorine is used, how many gallons per day of sodium hypochlorite is required to maintain a dosage of 3 ppm? The chemical weight of sodium hypochlorite is 9.17 lbs/gal.
187.65 gpd
18.76 gpd
20.5 gpd
None of these
Calculate the chlorine dose in ppm when a chlorinator is set to feed 12.5 lbs of chlorine per day. The flow is 380,000 gal/day.
1.8 ppm
3.9 ppm
4.5 ppm
None of these
Calculate the volume, in gallons, of the sedimentation basin that is 75 ft long, 26 ft wide, and 10 ft deep.
95,230 gallons
61,580 gallons
145,860 gallons
223,400 gallons
A circular tank has a diameter of 20 ft and is 7 ft deep. How many gallons will it hold?
46,000 gallons
238,000 gallons
16,441 gallons
326,434 gallons
What causes the water to look cloudy?
Dissolved solids
Bicarbonates
Hardness
Suspended material
What are colloidal particles?
Very small particles that do not dissolve and remain dispersed in a liquid for a long time due to their small size and electrical charge
Settleable solids
Large sized particles
Sand
Which of the following describes turbidity?
Inorganic salts
Calcium and magnesium
Soluble iron and manganese
Cloudiness or haziness of a fluid caused by suspended solids
What causes the water to look cloudy?
Dissolved solids
Bicarbonates
Hardness
Suspended material
What are colloidal particles?
Very small particles that do not dissolve and remain dispersed in a liquid for a long time due to their small size and electrical charge
Settleable solids
Large sized particles
Sand
Which of the following controls the efficiency of removing suspended solids in the sedimentation process?
Minimizing mudball formation
Sodium hydroxide
Flowrate
Proper backwashing
What are common filtration rates in gravity filtration?
0.1 to 1.9 gpm/sq. ft
11 to 20 gpm/sq. ft
2 to 10 gpm/sq. ft
21 to 28 gpm/sq. ft
How is turbidity measured?
Mg/L
Ppm
Percentage
None of the above
What is typically used to clean the sludge on the bottom of a rectangular clarifier?
Flash mixer
Eductor
Chain and flight collectors
Baffles
Filter backwash is triggered when:
A turbidity breakthrough occurs
Operator feels like backwashing it
PH is increased
Filter media is visible
Disinfection of a surface water supply, such as a lake, river, etc. Is for the purpose of:
Iron removal
Aiding in coagulation
Killing pathogens
Softening
Which acid is formed when chlorine is mixed with water?
Hydrobromic acid
Humic acid
Hypochlorous acid
Fulvic acid
A water supply has a flow of 550,000 gal/day. If solid high‐test‐hypochlorite (HTH) with 65% available chlorine (CL2) is used, how many pounds per day of HTH is required to maintain a dosage of 1.5 ppm?
10.6
251
3.5
None of these
Presence of total coliform bacteria in water means water is definitely contaminated by salmonella, E.coli, or some other type of pathogenic bacteria.
True
False
Plastic containers are commonly used for storage of chlorine gas.
True
False
When a water sample is positive for total coliform, the sample must be analyzed for fecal coliform or E.coli.
True
False
The number of monthly distribution samples bacteriological samples required by Total Coliform Rule is based on the number of water sources serving customers.
True
False
At any sample point in the distribution system, the presence of HPC more than or equal to 500 colony forming units per milliliter is equivalent to a detectable disinfectant residual.
True
False
Water delivered to the distribution system shall not contain a disinfectant residual of less than 0.2 mg/L for more than 4 hours in any 24-hour period (continuous disinfection).
True
False
Which one of the following factors affects CT?
Alkalinity
Color
Hardness
pH value
Conventional filtration combined filter effluent turbidity shall:
be less than or equal to 0.5 NTU 95% of time
never exceed 5.0 NTU
not exceed 1.5 NTU for more than one continuous hour
none of these
The two main softening methods used by treatment facilities are.
Reverse osmosis and oxidation
Distillation and disinfection
Ultraviolet radiation and electrodialysis
Ion-exchange and lime-soda ash
The two main substances that cause water hardness are _________________.
Benzene and cadmium
Calcium and copper
Manganese and calcium
Magnesium and calcium
Sources of taste and odor issues include _________________.
Raw water
Consumer plumbing
Distribution systems
All of the above
Extremely soft water can cause problems with pipes and fittings because it is _________________.
Corrosive
Full of suspended solids
Scale forming
Toxic
The most effective way of controlling taste and odor is:
Ignore it
Prevent it from occurring
Do not use treatment
None of these
Black stains on plumbing fixtures can be attributable to:
Manganese
Calcium
Magnesium
Copper
Fluoride is added to drinking water for:
Disinfection
Corrosion Control
Preventing dental cavities
Turbidity removal
The approved fluoride additive in U.S. is:
Sodium fluoride
Sodium fluorosilicate
Fluorosilicic acid
All of the above
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