D2 Practice 2 Flashcards
Which process converts ammonia to nitrite and nitrate?
Nitrification
What is the maximum advisable rate of chlorine gas removal from a 150 lb. cylinder?
40 lbs/day
What is a type of positive displacement water meter?
Nutating-disc meter
_____ is a power-operated mechanism for opening amd closing a valve.
Actuator
What is required if a routine sample tests positive for total coliform bacteria?
Take repeat samples
Why is a grid layout better than a tree (branching) layout for a water distribution system?
Less dead-end mains
In general, at what depths is shoring required for a trench, if you’re excavating in soil?
5 feet or deeper
What is the purpose of a reduced pressure principle assembly?
Prevents back-pressure and back-siphonage
What occurs after breakpoint chlorination is achieved?
Free available chlorine residual is directly proportional to the amount of chlorine added
What is used to automatically shut-off the flow into a tank when the water level reaches a predetermined level?
Altitude valve
What could be used to find a chlorine gas leak, which produces white smoke when it reacts with this substance?
Spray ammonia solution vapor near leak
What causes staining of plumbing fixtures?
Iron and manganese
How long should you flush the water before you collect a bacteriological sample?
As long as necessary to flush stagnant water from the service pipe
What is the purpose of a surge tank?
Protect pipelines from sudden high pressure
What is recommended if a chlorine gas cylinder is leaking?
Rotate the cylinder and turn the leak upwards
What is the purpose of primary MCL?
To protect human health
What problem could be caused by water with a pH of 5.3?
Corrosion
What is a common way to connect a new pipe to an existing pipe, while the latter is pressurized and in-service?
Wet tap or hot tap
What impact would organics have on chlorine demand?
Increase chlorine demand
What is dichloramine?
Combined chlorine residual
What impact does tuberculation have on the interior of a water main?
Causes rough interior of the water main due to corrosion
What is used to neutralize chlorine residuals when collecting a water sample for bacteriological analysis?
Sodium thiosulfate
What are electrodes and ultrasonic signals used for in a tank?
Monitor water level
Which part of the water main should a new service tap be installed?
45 degrees from the top of the water main
What is the purpose of a vacuum breaker?
Prevent back-siphonage
Which type of valve is commonly used to isolate water mains during repairs to minimize service outages?
Gate valve
Pumping water level - static water level=
Drawdown
What is purple pipe used for?
Reclaimed water
Where is the correct location to install an air release valve?
Top of pipe
What must be performed prior to entering a confined space?
Test for oxygen deficiency/enrichment, combustible gases, and toxic gases
What does the C-factor of a pipe represent?
Roughness of pipe interior
Why should you never empty an underground storage tank when the groundwater level is high?
It may float the tank and cause damage to the facility
What is used to determine the bacteriological quality of a water supply?
Presence-absence of coliform bacteria
Which valve is available as a swing, double door, or slanting disc?
Check valve
What is used to check the effectiveness of disinfection?
Test for coliform bacteria (bacteriological result)
What are used to protect water mains and tanks from corrosion?
Anodes
What is a common customer complaint during or immediately after flushing the water main?
Cloudiness and color in water
What is total dynamic head?
Total static head plus head loss, when pump is operating
What is a connection between a potable water system and an unapproved water supply?
Cross connection
What is tested in the field during the collection of a bacteriological sample?
Test for chlorine residual
Which type of water meter diverts some of the flow through a bypass meter, which is calibrated to register the total flow through the main pipeline?
Proportional meter
What must be true if trihalomethane is detected in the water?
Disinfection by-products have formed
What causes a pump to sound like it is pumping rocks?
Cavitation
What are the three most commonly used forms of chlorine for disinfection in the water industry?
Chlorine gas, calcium hypochlorite, and sodium hypochlorite
What will reduce flow rate in a pipe?
Encrustation
What is the source of E. coli?
Intestinal tract of warm-blooded animals
What is the primary purpose of a listening device?
Locate leaks
What does a positive result from a presence-absence test indicate?
Biological problem
Which part of a chlorinator is fitted with a Venturi nozzle, and creates a vacuum that moves the chlorine gas?
Ejector
What should be installed on the pipeline if the flow changes directions?
Thrust block or restraint
What has the least impact to the disinfection capabilities of chlorine?
Hardness
What is commonly used to protect the exterior of ductile iron pipe from corrosion?
Polyethylene encasement
What causes water to appear red?
Iron
What could be used to identify the corrosiveness of water?
pH
What will happen to the maximum flow rate from a chlorine gas cylinder if the temperature of the cylinder decreases?
Decreases
What is a white tablet with 65% available chlorine?
Calcium hypochlorite
Which type of water storage facility has a height that is greater than its diameter?
Standpipe
What is required if you cannot perform a bacteriological test within one hour of sampling?
Refrigerate the sample
What causes scaling in a pipe?
Hardness
Which valve has a movable disc that rotates on a vertical shaft to stop the flow of water?
Butterfly valve
What will happen if the pressure in the water main drops below zero?
Back-siphonage
What is a buried valve that connects a water main to a service lateral?
Corporation stop
What is one of the drawbacks of a dead-end water main?
You have to flush more
What is required before a new water main is placed in-service?
Test for coliform bacteria
A solution with a pH of 6 is a _______
Weak acid
What is required before discharging chlorinated water to the environment?
Dechlorinate the water
What is the purpose of painting or coating the interior of a steel tank?
Minimize corrosion
What’s an approved backflow prevention device for a service connection that does not pose a health hazard?
Double check valve
What is used to add head to water and convey it to higher elevations?
Booster pumps
Which standards are commonly used to disinfect a new water main?
AWWA
If the organic concentration in a new water main increases, what is the impact to chlorine demand?
Chlorine demand Increases
What are essential for killing harmful bacteria in water?
Adequate chlorine contact time and chlorine residual concentration
If a tank was disinfected due to possible contamination, what would be true?
It cannot be returned to service until bacteriological test results show that samples tested negative for coliform bacteria
What is used to prevent backflow into a pump?
Check valve
What is the primary problem with installing PVC pipe (C-900) near a gas station?
Gasoline can permeate into the pipe
What is a source of water main contamination that is unique to rural areas?
Septic leach fields
What is formed when chlorine reacts with natural organic matter?
Trihalomethane (THM)
An environment with the presence of free oxygen is known as ______
Aerobic
What could happen if the water pressure on the customer’s side exceeds the pressure in the water main?
Back-pressure
What is always required after coating the tank interior?
Disinfection
What is a process by which water vapor passes into the atmosphere from living plants?
Evapotranspiration
What is installed at the top of a well to prevent contamination of groundwater from the surface?
Sanitary seal
Safe access and egress, such as a ladder, must be located within ______ feet from all workers in a trench that is 4 feet or deeper
25
______ is a type of positive displacement pump
Reciprocating or piston pump
Underground layer of porous, water bearing material from which groundwater can be extracted using a well.
Aquifer
