Water distribution practice exam #2 (D1-D2) (2022/2023) graded A+

Water distribution practice exam #2 (D1-D2) (2022/2023) graded A+ Which process converts ammonia to nitrite and nitrate? Nitrification What is the maximum advisable rate of chlorine gas removal from a 150- pound cylinder? 40 pounds per day What is a type of positive displacement water meter? Nutating- disk meter What is a power-operated mechanism for opening and closing a valve? Actuator What is required if a routine sample test positive for total coliform bacteria? Take repeat samples Why is a grid layout better than a tree layout for a water distribution system? Less dead-end mains What is the purpose of a reduced pressure principle assembly? Prevents back-pressure and back-siphonage In general, at what depths is shoring required for a trench, if you're excavating in soil? 5 feet or deeper 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 pre-determined level? Altitude valve What would 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 & manganese How long should you flush 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 used by water with a pH of 5.3? Corrosión 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 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 vacuumed 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 ranks from corrosion? Anodes What is a common customer complaint during or immediately after fishing the water main? Cloudiness and color in water What is total dynamic head? Total static head plus head loss, when the pump is operating What is a connection between potable water system and an unapproved water supply? Cross connection What is tested in the field during the collection of 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 pipelines? 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 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 indentify 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? It decreases What is a white tablet with a 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 the 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 Which of the Following is a buried valve that connects a water main to a service lateral? Corporation stop What is one if the drawbacks of a dead-end water main? You have to flush more What is required before a new water main is placed in a 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 is an approved backflow prevention device for a service connection that does not pose a health hazard? Double check valve What 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 the essential for killing harmful bacteria in water? Adequate chlorine contact time and chlorine residual concentration If a tank has disinfected due to possible contamination, which of the following is 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 a 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 customers side exceeds the pressure in the water main? Back-pressure What is always required after costing the tank interior? Disinfection What is a process by which water vapor passed 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? 25 feet of a trench that is 4 feet or deeper What is a type of positive displacement pump? Reciprocating or piston pump What is an underground layer of porous water bearing material from which groundwater can be extracted using a well? Aquifer