Water Distro 2 set 2
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Free chlorine residual in water exists in two
forms. These are
- Hypochlorous acid
- and hypochlorite ion
When sodium hypochlorite is dissolved in water, which of the following is formed?
- Sodium hydroxide
- (lye, or caustic soda)
The sum of a disinfectant’s demand and its residual is equal
When chlorine gas is dissolved in water, two products are formed: hypochlorous acid and
The difference between the total chlorine
applied and the chlorine residual is
The device used to regulate and control the rate of feed of chlorine gas is called a
Chlorine residual is measured in the field using the
DPD colorimetric method
The fusible plug that is in all chlorine containers
Should never be removed or tampered with
The device that generates the vacuum conditions for chlorine gas application is called a
A chlorine leak can be detected by
Applying ammonia gas
A “B” repair kit is used to address equipment failures on
- One-ton chlorine
When chlorine gas is to be withdrawn from a one-ton container, you must use the
A chlorinator is feeding 240 pounds per day at a treatment plant operating at 24 MGD.
What is the current chlorine dosage rate in milligrams per liter?
mg/L = lb/day ÷ (8.34 x MGD)
= 1.2 mg/L
A treatment plant’s desired chlorine dosage rate is 3.5mg/L, and its current flow rate is 8000 gallons per minute.
What should the pounds per day setting be on
the plant’s chlorinator?
lb/day = mg/L x 8.34 x (MGD)
= 3.5 x 8.34 x (8000 gal/min x 1440 min/day ÷1,000,000 gal/Mgal)
= 336 lb/day
At the top of the “hump” in the chlorine breakpoint curve,
- All ammonia has
- been converted to chloramines
A distribution system operator measures a total chlorine residual of
1.25 mg/L, and a free chlorine residual of 1.15 mg/L. This indicates that
The system is operating to the right of the breakpoint on the breakpoint curve
From the first rising portion of the chlorine breakpoint curve through the top of the “hump”, the predominant form of residual chlorine is
In addition to indicating that bacteria may be present, nitrite acts as a
Of the following, which will have the greatest tendency to increase
b. Pipe materials
e. Diurnal variation
At what point on the breakpoint curve are we most likely to encounter
Near the breakpoint
In nitrification, bacteria consume excess ammonia in the water and produce
A distribution system operator measures a total chlorine residual of 1.25 mg/L. How many points on the chlorine breakpoint curve may display this residual?
When free chlorine is applied at a ratio of more than 5:1 versus
ammonia, chloramines will always be
Converted into nitrogen gas and nitrate
At the top of the “hump” in the chlorine breakpoint curve, the
chlorine-to-ammonia ratio is
A small amount of free chlorine is added to a water sample, but no chlorine residual is apparent. This is most likely due to the presence of which of the following in the raw water?
- Iron and/or
- hydrogen sulfide
Which of the following can be added along with chlorine to form
The total amount of free chlorine required to reach the breakpoint is known as the chlorine
Nitrification in distribution systems using chloramines requires the presence of
A new reach of 36-inch pipe containing 0.029 million gallons needs to
be disinfected with chlorine, using 50 mg/L.
How much chlorine gas must be applied in this procedure?
- 12 pounds =50 x 0.029 x 8.34
A reservoir requires 1000 pounds of chlorine gas for full
disinfection. How many pounds of calcium
hypochlorite granules (65% available chlorine) will this procedure require?
- 1540 pounds = 1000 pounds ÷ 0.65
A 1.5 million gallon reservoir requires a dosage of 10 ppm for disinfection. How many gallons of bleach (12.5% available chlorine, 9.5 lb/gal) will this procedure require?
105 gallons = (10 x 1.5 x 8.34) ÷ 0.125 ÷ 9.5
The total static head plus friction is a pump’s
Total dynamic head
Compared to axial flow pumps, radial flow pumps will exhibit a
Lower flow rate and a higher discharge pressure
The difference between water pressures upstream and downstream of a
pump when it is not in operation is known as the
Total static head
The water in a pump’s packing gland serves many purposes. Among these is that it
Flushes gritty material out of the packing area
The purpose of the packing in a centrifugal pump is
Comparable to a bearing since it is impregnated with lubricant
b. To prevent vibration of the shaft
c. To provide support for the impeller
d. To surround the bearings and lubricate them
e.None of the above
None of the above
Which of the following is a positive displacement pump?
The practical maximum suction lift for a centrifugal pump in good condition
20-feet to 25-feet
A type of pump that can cause discharge line rupture from over-pressurizing is
Pumps are primed to
- Replace air inside
- the pump with water
term for the water-containing portion of a centrifugal pump is the
Which of the
following is considered a radial flow pump?
A pump is operating in a flow range that provides an efficiency of 80 %. The 50 Hp electric motor that drives this
pump has an efficiency of 90 %. What is
the wire-to-water efficiency of this installation?
- 72 percent = 0.80 x 0.90 x 100%
Find the motor horsepower required for a pump that must move 1200 gpm against a TDH of 150 feet, if the pump efficiency is 75% and the motor efficiency is 90%.
- 67 Hp =(1200 x 150 ÷ 3960) ÷ 0.75 ÷ 0.90
Find the daily cost of operation of a 100-Hp pump, assuming continuous (24-hour) operation and
an electrical cost of 20 cents per kilowatt-hour.
$358 = 100 Hp x 0.746 kW/Hp x 24 hr
The formal document describing the potential impact of a hazardous material release on a utility’s neighbors, and which must be
submitted to the Federal Bureau of Investigation, is called the
Risk management plan
Which of the following gases is toxic at the lowest concentration?
Shoring is normally required for trenches of what minimum depth?
Egress is normally required for trenches of what minimum depth?
Which of the following would be considered a primary instrument?
a. Flow meter
c. Level detector
d.Chlorine residual analyzer
e.All of the above
Which of the following is the most likely to be a fuel involved in a Class B fire?
A confined space that contains a material that has the
potential to engulf an entrant is
A permit space
The cost of parts and labor for a new pump station is an example of
What condition must exist for an area to be considered a confined space?
a.Limited or restricted means of entry or exit
Is large enough for a person to enter and perform work
c.Is not designated for continuous occupancy
d.All of the above
e.None of the above
All of the above
The costs of maintenance labor and electricity for pump
operations are examples of
The progressive discipline procedure dictated by the Skelly process consists of
Counseling, verbal warning, written warning, suspension, and termination
A tank has an actual water level of 26 feet, and a maximum water level of 32 feet. What
should be the milliamp reading for the level gauge located at the tank bottom?
17 ma = [ 16 ma x (26ft ÷ 32 ft) ] + 4 ma
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