Water Distribution Practice Exam #2 (D1-D2) Questions and Answers 100% Correct, Exams of Water Resources Planning and Management

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Water Distribution Practice Exam #2 (D1- D2) Questions and Answers 100% Correct Which process converts ammonia to nitrite and nitrate? - ANSWER-Nitrification What is the maximum advisable rate of chlorine gas removal from a 150- pound cylinder? - ANSWER-40 pounds per day What is a type of positive displacement water meter? - ANSWER-Nutating- disk meter What is a power-operated mechanism for opening and closing a valve? - ANSWER- Actuator What is required if a routine sample test positive for total coliform bacteria? - ANSWER- Take repeat samples Why is a grid layout better than a tree layout for a water distribution system? - ANSWER-Less dead-end mains What is the purpose of a reduced pressure principle assembly? - ANSWER-Prevents back-pressure and back-siphonage In general, at what depths is shoring required for a trench, if you're excavating in soil? - ANSWER-5 feet or deeper What occurs after breakpoint chlorination is achieved? - ANSWER-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? - ANSWER-Altitude valve What would be used to find a chlorine gas leak, which produces white smoke when it reacts with this substance? - ANSWER-Spray ammonia solution vapor near leak What causes staining of plumbing fixtures? - ANSWER-Iron & manganese How long should you flush water before you collect a bacteriological sample? - ANSWER-As long as necessary to flush stagnant water from the service pipe What is the purpose of a surge tank? - ANSWER-Protect pipelines from sudden high pressure What is recommended if a chlorine gas cylinder is leaking? - ANSWER-Rotate the cylinder and turn the leak upwards What is the purpose of primary MCL? - ANSWER-To protect human health What problem could be used by water with a pH of 5.3? - ANSWER-Corrosión What is a common way to connect a new pipe to an existing pipe, while the latter is pressurized and in-service? - ANSWER-Wet tap or hot tap What impact would organics have on chlorine demand? - ANSWER-Increase chlorine demand What is dichloramine? - ANSWER-Combined chlorine residual What impact does tuberculation have on the interior of a water main? - ANSWER- Causes rough interior of the water due to corrosion What is used to neutralize chlorine residuals when collecting a water sample for bacteriological analysis? - ANSWER-Sodium thiosulfate What are electrodes and ultrasonic signals used for in a tank? - ANSWER-Monitor water level Which part of the water main should a new service tap be installed? - ANSWER-45 degrees from the top of the water main What is the purpose of a vacuumed breaker? - ANSWER-Prevent back siphonage Which type of valve is commonly used to isolate water mains during repairs to minimize service outages? - ANSWER-Gate valve Pumping water level - static water level = - ANSWER-Drawdown What is purple pipe used for? - ANSWER-Reclaimed water Where is the correct location to install an air release valve - ANSWER-Top of pipe What must be performed prior to entering a confined space? - ANSWER-Test for oxygen deficiency/enrichment, combustible gases, and toxic gases What does the C- factor of a pipe represent? - ANSWER-Roughness of pipe interior What is required before discharging chlorinated water to the environment? - ANSWER- Dechlorinate the water What is the purpose of painting or coating the interior of a steel tank? - ANSWER- Minimize corrosion What is an approved backflow prevention device for a service connection that does not pose a health hazard? - ANSWER-Double check valve What used to add head to water and convey it to higher elevations? - ANSWER-Booster pumps Which standards are commonly used to disinfect a new water main? - ANSWER- AWWA If the organic concentration in a new water main increases, what is the impact to chlorine demand? - ANSWER-Chlorine demand increases What are the essential for killing harmful bacteria in water? - ANSWER-Adequate chlorine contact time and chlorine residual concentration If a tank has disinfected due to possible contamination, which of the following is true? - ANSWER-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? - ANSWER-Check valve What is the primary problem with installing a PVC pipe ( C-900 ) near a gas station? - ANSWER-Gasoline can permeate into the pipe What is a source of water main contamination that is unique to rural areas? - ANSWER- Septic leach fields What is formed when chlorine reacts with natural organic matter? - ANSWER- Trihalomethane ( THM ) An environment with the presence of free oxygen is known as? - ANSWER-Aerobic What could happen if the water pressure on the customers side exceeds the pressure in the water main? - ANSWER-Back-pressure What is always required after costing the tank interior? - ANSWER-Disinfection What is a process by which water vapor passed into the atmosphere from living plants? - ANSWER-Evapotranspiration What is installed at the top of a well to prevent contamination of groundwater from the surface? - ANSWER-Sanitary seal Safe access and egress such as a ladder must be located? - ANSWER-25 feet of a trench that is 4 feet or deeper What is a type of positive displacement pump? - ANSWER-Reciprocating or piston pump What is an underground layer of porous water bearing material from which groundwater can be extracted using a well? - ANSWER-Aquifer