California Water Treatment Operator Exam: all 223 questions with answers

Each question leads to its own page with the answers and the solution.

• Source Water39 questions
• Water Treatment Processes49 questions
• Operation and Maintenance36 questions
• Laboratory Procedures26 questions
• Regulations and Administrative Duties31 questions
• Treatment Exam Math42 questions

Source Water

• 1001Which source of water is generally LEAST affected by rapid changes in turbidity after a storm?
• 1002The continuous movement of water between the oceans, atmosphere and land is called the
• 1003An aquifer that is bounded above and below by layers of low permeability and is under pressure is called
• 1004The top surface of the saturated zone in an unconfined aquifer is called the
• 1005What is the static water level in a well?
• 1006A well has a static water level of 85 ft and a pumping water level of 112 ft. What is the drawdown?
• 1007A well produces 450 gpm with a drawdown of 30 ft. What is the specific capacity of the well?
• 1008The lowering of the water level around a pumping well, shaped like an inverted cone, is called the
• 1009Which part of a drilled well prevents the walls of the borehole from collapsing and keeps surface contamination out of the aquifer?
• 1010What is the purpose of the sanitary seal (annular seal) around a well casing?
• 1011Which well component is the slotted or perforated section that allows groundwater to enter while holding back sand?
• 1012Before a new or repaired well is placed in service, it is normally
• 1013Which of the following is a common sign that a well may be pumping air or sand?
• 1014A sudden increase in the drawdown of a well with no change in the pumping rate most likely indicates
• 1015Which watershed activity is the greatest threat to a surface water supply used for drinking?
• 1016A watershed sanitary survey is conducted to
• 1017Water in a deep reservoir often forms layers in summer because
• 1018Reservoir turnover in the fall or spring can cause treatment problems mainly because it
• 1019Why do many reservoir intakes have multiple withdrawal levels?
• 1020Which condition in a reservoir is most associated with taste and odor complaints in the summer?
• 1022A raw water pH of 5.8 compared with the normal range of 7.2 to 7.6 should be recognized as
• 1023Which of the following would most likely cause raw water to have a sudden, strong chemical or fuel-like odor?
• 1024Which contaminant is a microbial contaminant commonly found in surface waters affected by animal waste?
• 1025Groundwater under the direct influence of surface water is of concern because
• 1026Which chemical compounds in water are the main cause of hardness?
• 1027Which of the following is a common problem caused by hard water?
• 1028Alkalinity in natural water is mainly caused by
• 1029A water storage tank is 60 ft in diameter. How many gallons are in one foot of depth?
• 1030A rectangular basin is 40 ft long, 20 ft wide and has water 10 ft deep. How many gallons does it hold?
• 1031Which device is used to measure the flow in an open channel?
• 1032A magnetic flow meter measures flow by
• 1033Which type of flow meter creates a pressure difference across a narrowing in the pipe to calculate flow?
• 1034Water storage tanks should be disinfected after cleaning or repair mainly to
• 1035Which of the following is a recognized potential security risk at a water treatment facility?
• 1036What is pretreatment of a raw surface water supply meant to accomplish?
• 1037One acre-foot of water is equal to approximately
• 1038Water at the bottom of a storage tank 50 ft deep exerts a pressure of about
• 1039A pressure gauge on a pipe reads 52 psi. What is the equivalent head in feet?
• 1040Seasonal snowmelt in the watershed usually causes the raw water to

Water Treatment Processes

• 2001What is the main purpose of coagulation in water treatment?
• 2002Which chemical is most commonly used as a primary coagulant in drinking water plants?
• 2003Rapid (flash) mixing is used in a coagulation process to
• 2004Flocculation basins use slow, gentle mixing because
• 2005Which condition generally makes alum coagulation LESS effective?
• 2006When alum is added to water, it consumes alkalinity. If the raw water alkalinity is too low, the operator may need to add
• 2007What is the purpose of a sedimentation basin?
• 2008Tube settlers or plate settlers improve sedimentation mainly by
• 2009Floc that is small and cloudy (pin floc) and does not settle well may indicate
• 2010A jar test is performed to
• 2011A sedimentation basin is 40 ft long, 20 ft wide and 12 ft deep and receives a flow of 0.5 MGD. What is its detention time?
• 2012What is the primary purpose of filtration in a water treatment plant?
• 2013Turbidity in water is a measure of
• 2015The rate at which water is applied to a filter, expressed in gpm per square foot of surface area, is the
• 2016As a filter run progresses, head loss across the filter normally
• 2017Which event is the main trigger for backwashing a filter?
• 2018What is the effect of backwashing a filter too long at a high rate?
• 2019What is surface wash used for in a filter backwash?
• 2020A filter has an area of 200 sq ft and a backwash rate of 15 gpm/sq ft. What is the backwash pumping rate?
• 2021A filter with an area of 400 sq ft produces 2.88 MGD. What is the filtration rate in gpm/sq ft?
• 2022Which of the following is a purpose of disinfection?
• 2023Which gas is commonly fed as a primary disinfectant in water treatment, and is stored as a liquid under pressure in cylinders?
• 2024What is the approximate available chlorine content of commercial sodium hypochlorite (liquid bleach) used at water plants?
• 2025Which form of chlorine is most effective as a disinfectant?
• 2026Chlorine demand is defined as
• 2027A plant adds 3.2 mg/L of chlorine and has a free chlorine residual of 0.8 mg/L. What is the chlorine demand?
• 2028The point where adding more chlorine produces a rise in free chlorine residual in proportion to the dose is called
• 2029What is the main reason chloramines are used as a secondary disinfectant in some distribution systems?
• 2031The CT value used in disinfection is calculated as
• 2032A clearwell provides a T10 contact time of 40 minutes with a free chlorine residual of 1.2 mg/L. What is the CT?
• 2033If the required CT is 60 mg/L-min and the actual CT is 90 mg/L-min, the inactivation ratio is
• 2034Which of the following disinfection byproducts is regulated as total trihalomethanes (TTHM)?
• 2035Which action is most effective for reducing the formation of disinfection byproducts in a treatment plant?
• 2036Which treatment technique is commonly used to control corrosion of lead and copper in a distribution system?
• 2037Water that is corrosive generally has
• 2038Which of the following is a sign of a corrosion problem in the distribution system?
• 2039Which of the following is a common taste and odor control method at a treatment plant?
• 2040A musty or earthy odor in a surface water source in the summer is often caused by
• 2041Which two metals are most commonly removed from groundwater because they cause staining and taste problems?
• 2043Iron and manganese are often removed by
• 2044Fluoride is added to water systems to
• 2046Best Available Technology (BAT) as used in drinking water regulation refers to
• 2047Which technology is a recognized BAT for removing arsenic from drinking water?
• 2048Which process is a common treatment to remove nitrate from groundwater?
• 2049Granular activated carbon filters remove organic chemicals mainly by
• 2050Which chemical is generally added to water after filtration to raise the pH and reduce corrosion?
• 2051Which sequence correctly lists the steps in conventional surface water treatment?
• 2052Direct filtration differs from conventional filtration because it
• 2053Which disinfectant provides a lasting residual in the distribution system?

Operation and Maintenance

• 3001A centrifugal pump that runs but delivers little or no water immediately after being started has most likely lost its
• 3002What is cavitation in a pump?
• 3003Which pump type moves water by trapping fixed volumes and is often used for chemical metering?
• 3004Why should a positive displacement pump never be started against a closed discharge valve?
• 3005A centrifugal pump is operated with its discharge valve closed for a long time. What is the most likely result?
• 3006What is the main purpose of the packing gland on a pump with packed stuffing box?
• 3007A mechanical seal is used on a pump shaft instead of packing because it
• 3008Which type of valve is best suited for throttling flow?
• 3009A check valve is installed on a pump discharge line to
• 3010Water hammer is caused by
• 3011An operator hears a loud grinding noise and notices that a pump motor is running hot. The first action should be to
• 3012Lubricating a motor bearing with too much grease can cause
• 3013What does an ammeter reading higher than the nameplate full-load amps on a pump motor suggest?
• 3014Lock-out/tag-out procedures must be followed before
• 3015A diaphragm metering pump is feeding too little chemical. A likely cause is
• 3016To calibrate a chemical feed pump, an operator would normally
• 3017A chemical feed pump is set to deliver 40 mL per minute. How many gallons per day is that? (1 gal = 3,785 mL)
• 3018Which of the following is a function of an anti-siphon (back pressure) valve on a chemical feed line?
• 3019A dry chemical feeder that delivers a measured weight or volume of powder per time is called a
• 3020Chlorine gas feed systems often use a vacuum regulator because
• 3021What is the purpose of a venturi or ejector in a chlorine gas feed system?
• 3022A water meter that measures flow by the movement of a spinning rotor or turbine inside the pipe is a
• 3023A meter reads 458,320 gallons on Monday morning and 512,820 gallons on Tuesday morning. What was the daily use in gallons?
• 3024The accuracy of a flow meter is checked by
• 3025A pressure gauge on a pump discharge reads 0 psi while the pump is running. This most likely indicates
• 3026Total dynamic head of a pump is the
• 3027What does SCADA stand for in water treatment?
• 3028In a 4 to 20 mA instrument signal, 4 mA normally represents
• 3029A transmitter ranges 0 to 100 gpm on a 4 to 20 mA signal. The signal reads 12 mA. What is the flow?
• 3030A standby generator at a treatment plant should be
• 3031An automatic transfer switch is used to
• 3032A blower or compressor that produces unusually high vibration and noise should be
• 3033The primary function of a surge tank or hydropneumatic tank is to
• 3034Which operating practice reduces the number of pump starts per hour and protects the motor?
• 3035An on-line chlorine analyzer shows a steady reading that disagrees with a grab sample test. The operator should first
• 3036Which of the following helps prevent damage to a well pump motor from running dry?

Laboratory Procedures

• 4001Which container is required for a routine bacteriological (coliform) sample?
• 4002Why is the sample tap flame-sterilized or disinfected before collecting a bacteriological sample?
• 4003Chain of custody documentation for a sample records
• 4005Free chlorine in a water sample is most often measured in the field with
• 4006A DPD chlorine test must be run immediately after sampling because
• 4007The difference between total chlorine and free chlorine is the
• 4008A colorimeter measures the concentration of a substance by
• 4009The pH scale measures
• 4010A water sample with a pH of 5 is how many times more acidic than a sample with a pH of 7?
• 4011A pH meter is calibrated using
• 4012Turbidity is measured with a
• 4013Which of the following will give a false high turbidity reading?
• 4014Which standard is used to calibrate a turbidimeter?
• 4015Specific conductance of water is a measure of
• 4016Alkalinity is measured by titrating the sample with
• 4017Total hardness is expressed in the laboratory as
• 4018Which method uses a color change to show the presence of coliform bacteria in a 100 mL sample with only a yes or no answer?
• 4019The heterotrophic plate count (HPC) is used to
• 4020Which action reduces the risk of cross-contamination when dealing with reagents in a lab?
• 4021Safety Data Sheets (SDS) for each laboratory chemical give information on
• 4022When diluting concentrated acid in the lab, the correct procedure is to
• 4023If 10 mL of a stock solution is diluted to a final volume of 100 mL, the dilution factor is
• 4024You need 500 mL of a 2 mg/L solution from a 100 mg/L stock. How many mL of stock are required?
• 4025A sample for a metals analysis such as lead should be preserved by
• 4026When collecting a sample from a well, the operator should first
• 4028The Standard Methods approved procedure for analyzing a regulated compliance parameter must be followed because

Regulations and Administrative Duties

• 5001The federal law that gives EPA authority to set national drinking water standards is the
• 5002A Maximum Contaminant Level (MCL) is
• 5003Primary drinking water standards are set to protect
• 5005The Consumer Confidence Report (CCR) is
• 5006The Surface Water Treatment Rule requires systems using surface water to
• 5007A 3-log reduction of Giardia corresponds to a removal or inactivation of
• 5008Which rule regulates lead and copper at the customer's tap?
• 5009Under the Lead and Copper Rule, the copper action level is
• 5010Under the federal Lead and Copper Rule, an action level is exceeded when
• 5011The Revised Total Coliform Rule is based mainly on
• 5012A routine total coliform sample comes back positive. The required response is to
• 5013An E. coli-positive result after a total coliform-positive routine sample leads to
• 5014Tier 1 public notification must be given within
• 5015Which regulation addresses disinfectants and their byproducts in public water systems?
• 5016The MCL for total trihalomethanes (TTHM) is
• 5017The maximum residual disinfectant level (MRDL) for chlorine and chloramines is
• 5018Which regulation requires systems to protect groundwater sources from fecal contamination through sanitary surveys and corrective action?
• 5019The Filter Backwash Recycling Rule applies to systems that
• 5022In California, the drinking water operator certification program is administered by the
• 5023Which operator certification grade is the lowest drinking water treatment grade in California?
• 5024Public notification of a drinking water violation must tell customers
• 5025The Cryptosporidium action plan is mostly meant to help a plant
• 5026Which of the following agencies sets national drinking water standards?
• 5027Which of the following is a chemical hazard associated with mixing sodium hypochlorite and an acid?
• 5028Before entering a confined space such as a tank, the operator must
• 5029What does an oxygen reading of less than 19.5 percent in a confined space mean?
• 5030A self-contained breathing apparatus (SCBA) is used to
• 5031Which of the following should an operator do if a chlorine gas leak is found?
• 5032Which type of record should the operator keep in the plant daily log?
• 5034The Unregulated Contaminant Monitoring Rule is intended to
• 5035A system that serves the same people year-round, such as a city or mobile home park, is classified as a

Treatment Exam Math

• 6001A plant treats 2.5 MGD and the chlorine dose is 2.0 mg/L. How many pounds of chlorine are needed per day?
• 6002A well delivers 1.5 MGD and the desired chlorine dose is 3.5 mg/L. How many pounds of chlorine gas are needed per day?
• 6003A plant needs 20 lb/day of available chlorine and uses calcium hypochlorite that is 65 percent available chlorine. How many pounds of the hypochlorite are needed per day?
• 6004A plant treats 3.2 MGD with a chlorine dose of 1.8 mg/L using 12.5 percent sodium hypochlorite. About how many pounds of the hypochlorite solution are needed per day?
• 6005A pump delivers 3,500 gpm. What is the flow in MGD?
• 6006A plant flow of 2.0 MGD is equal to how many gallons per minute?
• 6007A flow of 3 MGD is equal to how many cubic feet per second (cfs)?
• 6008Water flows at 800 gpm through a 12-inch pipe. What is the approximate velocity in ft/sec? (1 cfs = 449 gpm)
• 6009A cylindrical storage tank has a diameter of 40 ft and a water depth of 25 ft. How many gallons are in the tank?
• 6010A clearwell holds 250,000 gallons and the plant flow is 1.2 MGD. What is the detention time?
• 6011A basin holds 30,000 gallons and the flow is 500 gpm. What is the detention time in minutes?
• 6012A well has a specific capacity of 12 gpm per foot of drawdown. If the drawdown is 40 ft, what is the well yield?
• 6013A pump discharge has a head of 150 ft. What is the pressure at the bottom of that column of water in psi?
• 6014The water level in a tank is 28 ft above a pressure gauge. What pressure should the gauge read?
• 6015How many pounds of dry chemical are in 50 gallons of a 10 percent solution, if the solution weighs 8.34 lb/gal?
• 6016A 0.25 percent solution contains how many mg/L of chemical? (1 percent = 10,000 mg/L)
• 601712 lb of dry chemical is dissolved in 100 lb of water. What is the percent strength of the solution?
• 6018How many gallons of a 1 percent solution can be made from 5 gallons of a 12 percent solution?
• 6019A plant treats 2 MGD with a chlorine dose of 2.5 mg/L using 12.5 percent hypochlorite weighing 10 lb/gal. How many gallons per day of solution are needed?
• 6020A chemical feed pump must deliver 33.4 gal/day. What setting in mL/min is needed? (1 gal = 3,785 mL)
• 6021The chlorine demand of a water is 2.3 mg/L. How much chlorine must be fed to leave a 1.0 mg/L residual?
• 6022A plant uses 45 lb/day of chemical that costs $0.85 per pound. What is the daily chemical cost?
• 6023A community of 12,000 people uses 150 gallons per capita per day. What is the average daily demand?
• 6024A filter has an area of 300 sq ft and operates at 4 gpm/sq ft for 24 hours. How many gallons are produced?
• 6025A filter with an area of 250 sq ft is backwashed at 20 gpm/sq ft for 8 minutes. What volume of backwash water is used?
• 6026A backwash rate of 15 gpm/sq ft is equal to a rate of rise of approximately
• 6027A sedimentation basin with a surface area of 2,500 sq ft receives 1.0 MGD. What is the surface loading rate?
• 6028A basin has a total weir length of 150 ft and a flow of 1.2 MGD. What is the weir overflow rate?
• 6029A required CT is 36 mg/L-min and the chlorine residual at the end of the clearwell is 1.5 mg/L. What minimum contact time is needed?
• 6030A pump moves 1,000 gpm against a total head of 99 ft. What is the water horsepower?
• 6031The water horsepower of a pump is 25 hp and the pump efficiency is 80 percent. What is the brake horsepower?
• 6032A pump requires 31.25 brake horsepower and the motor is 90 percent efficient. What motor horsepower is required?
• 6033A 40 hp motor runs 24 hours at an electricity cost of $0.12 per kWh. What is the approximate daily cost? (1 hp = 0.746 kW)
• 6034Water flows at 3 ft/sec through an 8-inch pipe. What is the flow in cubic feet per second?
• 6035A water meter reads 1,245,300 gallons on Monday and 1,578,300 gallons three days later. What is the average daily flow?
• 6036How long will it take to fill a 120,000 gallon tank at 500 gpm?
• 6037A reservoir holds 600,000 gallons. Inflow is 300 gpm and demand is 1,100 gpm. How many hours can the supply last?
• 6038How many pounds of chemical are in 3 MG of water dosed at 4 mg/L?
• 6040Raw water turbidity is 12 NTU and the filtered water is 0.3 NTU. What is the percent removal?
• 6041A reservoir covers 40 acres with an average depth of 12 ft. About how many million gallons does it hold? (1 acre-foot = 325,851 gal)
• 6042How much does 2,500 gallons of water weigh?
• 6043A hardness of 5 mg/L is equal to how many grains per gallon? (1 gpg = 17.1 mg/L)