ADEQ Water Treatment 2 Practice Test

These questions are part of the practice quiz. Start practicing

• What is the minimum free chlorine residual at the customer tap that is considered acceptable for ongoing disinfection?
• What is hardness caused by?
• Where is the heater located that vaporizes any chlorine liquid that may develop downline from an online one-ton container?
• Why are primary standards or MCLs enforceable by law?
• What unit is used to report arsenic concentration in drinking water standards?
• In the completed test of the multiple-tube fermentation method, a small portion of a coliform colony from the confirmed test that is positive is transferred to a growth medium and inoculated for _______, and a second portion is transferred to _______ and incubated for _______.
• Air binding can cause which of the following effects on flow?
• Which fires require a Class D fire extinguisher?
• What can greatly reduce fire hazards?
• Reverse osmosis membranes need cleaning if the pressure drop through the unit increases by what percent?
• What is the purpose of using granular activated carbon after ozone treatment, as described?
• What is the new MCL for uranium established by the final Radionuclides Rule?
• Without pretreatment, which membrane processes must be used to remove dissolved organic matter?
• Chlorite monitoring is required only for systems using ______
• What is the typical backwash rate for resin beds?
• Which health indicator may suggest a child has been exposed to high lead levels?
• An organic compound from components of pipe, coatings, and joint adhesives would most likely include...
• The primary purpose of covering an algae-prone impoundment is to
• The analysis of a water sample yielded a result of 4.0 mg/L CO2. What is the most likely source of this water sample?
• Microfiltration sits between ultrafiltration and multimedia filtration based on pore size. Which option correctly lists those adjacent stages?
• When disinfecting with chloramines, when can the ammonia be added to the process?
• A Leopold filter bottom is a patented filter underdrain system using a series of perforated _______ with channels to carry the water.
• Greensand filters are often capped to enhance filter performance and backwash efficiency. It is common to cap them with...
• A common problem with hyperchloronators is ________
• What is the one objective of a safety program?
• Lamella plates create flow by
• A gas chromatography-mass spectrometer would be used to determine ______ in a sample.
• Which material sits on the top in the standard bottom-to-top arrangement of higher-rate filter media?
• In water treatment, chelation is applied primarily to prevent which condition?
• Under Stage 1 disinfection byproduct rules, haloacetic acids are measured in which unit?
• Which unit is commonly used to express viscosity in the Saybolt Universal system?
• Lime softening effect on disinfection
• Which regulation governs microbial monitoring in drinking water distribution systems?
• The major provisions of the LT1ESWTR include the control of ____ and ______ turbidity performance standards.
• Besides oxidizing iron and manganese, potassium permanganate has been found to be most effective in controlling...
• Which structural feature do buttress dams rely on to transfer the water load?
• Ammonia is an inorganic compound occurring ______
• In lime-soda ash softening, what are used to help gather the fine calcium and magnesium precipitates into particles that will readily settle?
• What filter types would be best for direct filtration?
• Separate refrigerators should be used for the storage of _____ and ______ because the fumes of some chemicals may be harmful to ______.
• Define anion.
• What information can particle counters provide about particles?
• What piece of laboratory equipment can be made of polycarbonate and is clear, such that there is no confusion over reading the meniscus?
• Noncarbonate hardness is defined as
• Caustic soda is also known as which option?
• Greensand filters are often capped to enhance filter performance and backwash efficiency. It is common to cap them with...
• In open filters, which media arrangement provides superior removal of organics?
• _____ pipettes are used for performance monitoring and should be ______
• Which source water type is commonly associated with iron and manganese presence?
• A coagulant aid primary benefit is to reduce the amount of coagulant used.
• Superchlorination is typically used when ______ are excessive
• How are manganese greensand beds regenerated in typical treatment systems?
• Which oven is used to burn solids?
• Alum sludge dewatered in a lagoon for a year may still contain more than ______ of the original water.
• ______ or small streams at the upper end of a reservoir can help reduce _____
• Reverse osmosis units also have cartridge filters installed immediately ahead of the RO unit to remove suspended matter down to _____.
• What should be done to a shaft after an old sleeve is removed and before a new sleeve is installed?
• When do bar or wire-mesh screens usually encounter the largest amount of debris?
• In lime softening, the precipitated solids are which of the following?
• What is the typical detention time for the recarbonation process?
• Emergency response at a water treatment facility is governed under which combination?
• In an electrolyte solution, an anion is attracted to which electrode?
• The flow through a sedimentation basin should not exceed...
• What genus type or organism has killed the most people because of its high mortality rate when contracted?
• Driven wells are practical only when the water-bearing formations are relatively close to the surface and no contaminants exist in the soil. Which option best reflects this condition?
• An organic compound from components of pipe coatings and joint adhesives would most likely include which class of compounds?
• Color in the ______ range is determined by a visual comparison of the sample with either a known colored chemical solution or a calibrated color disk.
• Garnet sand is used at the bottom medium in multimedia filters because it is finer and greater density compared to the other sand in the filter. Which option best describes this characteristic?
• Lamella plates work by
• At pH levels associated with softening chemical precipitation, which component in the treated water may increase?
• In manganese greensand filters, the greensand is usually capped with at least _____
• Which of the following defines carbonate alkalinity?
• Which chemical family is used to regenerate ion-exchange systems and lower the pH of water treated by membrane processes?
• What is the best solution for iron problems when using exchange resins?
• What has caused a significant increase in environmental aluminum exposure?
• Ozone may convert large organic molecules into smaller ones. These BDOC compounds serve as food for which organisms?
• Disinfection byproducts increase as ______ increases, and low pH favors ______ and high pH favors ______.
• The LT2 Enhanced Surface Water Treatment Rule added tests that were not in the original rule. Which tests were added?
• A conical tank in which the softening reactions take place as the water passes upward through the unit is described as what type of reactor?
• What is the best way to deal with accidents or safety incidents?
• Regarding the USEPA sampling frequency for radionuclides in drinking water for individual contaminants at each entry point: If results of testing are below the detection limit of an approval method, what is the frequency of sampling?
• How often must an ozone-using system monitor bromate at the distribution system entry point?
• According to best practices, tip speed of the last flocculator should be about ______ and operate in the range of _______.
• What should be used to clean an old bearing?
• Which statement is true about the Contaminant Candidate List (CCL)?
• Surface washers should be turned off ____ min before the end of the main backwash.
• If coliforms are present, the gas they produce will begin to form bubbles in each inverted vial within what period?
• What membrane process will remove dissolved solids?
• Waterborne disease outbreaks have historically been traced to inadequate disinfection of drinking water. Which disease among the following has been linked to this issue?
• Methane dissolved in water will cause which taste?
• Chlorine dioxide has gained popularity because it:
• Among the VOCs found in groundwater, which are encountered most frequently and in the highest concentrations?
• What information can particle counters provide?
• Which organization established regulations for new chemical contaminant testing?
• How do the Surface Water Treatment Rules define surface water?
• Which statement best describes manganese dioxide (MnO2) in soils?
• The cleaning of microfiltration membranes helps maintain a stable ______ while keeping recovery at or above _______.
• How many grains are in 1 pound?
• A treatment plant's effluent water quality would be best shown from a sample collected _____.
• What should an operator do if hardness leakage is excessive immediately following a regeneration stage?
• In water treatment, which compound is described as looking like broken glass crystals?
• Which measuring and transmitting level device works readily on a 4-20 mA system but needs a temperature correction?
• The solubility of calcium carbonate in water decreases as temperature increases.
• The concentration of a disinfectant multiplied by the contact time from application to first customer must be calculated ______.
• Before reinstalling a shaft sleeve or impeller, which cleaners should be used?
• In the lime-soda ash process, what will cause increased solubility of taste and odor causing compounds?
• Compared to Stage 1 Disinfectants and Disinfection Byproducts Rule (DBPR), what major change was made when Stage 2 DBPR was promulgated?
• Soft water is defined as CaCO3 equivalents below what value?
• Continuous regeneration (CR) is usually used in greensand filters when ________ is mostly being removed and intermittent regeneration (IR) when __________ is mainly being removed. The _________ regeneration is used while the filter is offline.
• Which parameter is not part of the Langelier saturation index calculation?
• Compared to conventional sedimentation, dissolved air flotation achieves what with cryptosporidium removal?
• Which pipette type is used for performance monitoring and should be Class A?
• What factor explains why the bulk density shipping weight differs from laboratory density?
• Which statement about pump lubrication is false?
• Which treatment chemical raises pH?
• Caustic soda is also known as
• What scale prevention chemical can loosen existing deposits and cause red-water complaints?
• Which chemical used for oxidizing iron and manganese will react with hydrogen sulfide, cyanides, phenols, and other taste and odor compounds and will not form trihalomethanes?
• Point-of-use activated carbon filters are most effective for removing _________.
• Which statement about high iron and manganese in water is true?
• A specific-ion meter resembles a _______ except for the addition of a ______ and a provision for a selective-ion electrode.
• Threshold odor tests on the raw water and finished water while PAC is being fed should be performed at least
• Methyl orange used as an indicator in titrations is ______ on the alkaline side and _______ on the acid side.
• Where is arsenic found naturally?
• The most used conductor metal is?
• What is the main source of chlorite in drinking water?
• Why is electrical power entering a water treatment facility usually routed through transformers?
• Which chemical is primarily responsible for precipitating magnesium hydroxide during lime-softening?
• Stage 2 DBPR includes a provision to reduce or eliminate the use of chlorine disinfectants at the beginning of the treatment process if TOC exceeds 2.0 mg/L.
• When did the Long-Term 2 Enhanced Surface Water Treatment Rule take effect for large systems?
• Lamella plate or tube settlers with angles of ______ would require backflushing or manual cleaning to remove built-up sludge?
• Which pair of colors is not assigned numerical color units?
• Which type of process control can be used if accuracy is not critical?
• A gravity dam resists both ______.
• Excessive algae growth in a presedimentation impoundment is best controlled by:
• Which pump configuration allows the discharge to be oriented in any direction around the axis?
• Which option is NOT a purpose of polyphosphate addition in softening water?
• The rationale for dividing public water systems into three groups is the ______ of persons using the water.
• The Long-Term 2 Enhanced Surface Water Treatment Rule also calls for continuous monitoring at the entry point to the distribution system with a minimum of ______ of chlorine residual.
• Which errors often cause inaccurate iron and manganese test results?
• Under the Emergency Response Planning Guidelines #2, what is the maximum airborne concentration of chlorine below which nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects that could impair an individual's ability to take protective action?
• Which process is currently used for softening brackish water?
• What best describes an operator taking an active role in safety?
• Using dry ice or liquid CO2 as a diffuser gas results in smaller diffuser pipes.
• Which list identifies contaminants not regulated by current standards and monitored for potential future regulation?
• The C x T value is calculated using most or part of the treatment plant, some distribution piping, and to the _______.
• What is molecular weight?
• Why are drinking water regulations sometimes called interim regulations?
• Which agency defines the risk bins used to classify surface water sources under LT2?
• Define divalent.
• Alternate statement about the cations usually present in water in significant concentration: Which ions are usually the primary hardness contributors in water?
• Which chemical is used as a corrosion inhibitor in water treatment?
• Ozone is more stable in water when the water has which condition?
• Minimum hardness achievable by lime-soda ash process
• Which alum sludge dewatering method can attain at least 20% solids by weight?
• Which chemical is used to remove noncarbonate hardness in chemical precipitation softening?
• Diatomaceous earth filtration is used for raw water that has a maximum turbidity of ____.
• Hydraulic fracturing uses pressure to force ______ into existing fractures to open and separate different _____.
• Which of the following is not a part of a bearing?
• HPC method, and how long are samples incubated?
• Absolute ratings for membranes are based on which pore-size measure?
• Which term describes a water's buffering capacity?
• A filter core sample is best collected for solids retention analysis when
• What compounds are formed when calcium and magnesium are precipitated out of water in the lime softening process?
• What byproduct is most associated with chlorine dioxide used for disinfection?
• Manganese is naturally found in soils primarily as _______ and in the two forms of _______.
• A bacterial slime layer prevents the deposition of ______, and when the slime occasionally gets sloughed away, the slime carries away ______ and leaves the pipe surface bare.
• Cyanide affects which body systems?
• What is an ion?
• Drinking water containing copper well above the action level will most likely cause _______.
• Which chemical is used to regenerate manganese greensand beds?
• In SUVA calculation, which pairing is correct?
• Under the Stage 1 Disinfectants and Disinfection Byproduct Rule, the maximum contaminant level for haloacetic acids is 60 micrograms/L.
• Which byproduct is formed when ozone is used for disinfection and is commonly monitored for public health protection?
• Under favorable conditions, combined chlorine, such as monochloramine and dichloramine, compared to the bactericidal action of free chlorine would require ____ times more combined chlorine residual.
• The low-cost radioactive scan threshold for further analysis is normally the ______ for ______ or ______ but can be varied by the state agency.
• Fluoride injection should be kept away from which type of chemical?
• What is the main consideration in determining the length of the service stage of an ion exchange softener?
• A calcium sulfate molecule would be considered a dissolved solid.
• It is recommended that operators using particle counters track particles in the size range ______ because they are a possible surrogate for _______.
• What is the only reliable method of detecting hydrogen sulfide in the air?
• Which organization issued the Risk Management Rule in 1996 in an effort to protect public health and safety (nonemployees)?
• When alum is added to water, it causes the pH to _______, and when ferric salts are added to water, it causes the pH to ________.
• The sediment from presedimentation systems can be kept if samples are collected _________.
• Diatomaceous earth filtration maximum turbidity value?
• What is a disadvantage of using caustic soda to soften hard water compared to other chemicals?
• What is the filter bed used for in the softening process?
• After microscreening, there should be a significant reduction in _________.
• If a radionuclide is above the MCL in finished water, how often must sampling be done and for how long?
• Point-of-use activated carbon filters are most effective for removing ______.
• Which option lists the correct formula for caustic soda?
• The chlorine-measuring method that uses a gas-permeable membrane is the polarographic method.
• What is the required minimum alkalinity (as CaCO3) for manganese greensand filters?
• What indicates that water produced by a well is being drawn from more than one aquifer?
• What are the three forms of carbonate hardness?
• In a presedimentation impoundment, which option would most directly limit algae growth by reducing light exposure?
• To determine a safe stopping distance behind the vehicle in front, you should consider
• When using calcium hypochlorite, calcium carbonate scaling can occur on the suction and discharge sides of the pump. What is the best solution?
• Define cation.
• Which component of the softening system is primarily responsible for removing suspended solids before the main treatment?
• Phenolphthalein acidity is prevalent above which pH value?
• In regenerating ion-exchange systems and lowering the pH of water treated by membrane processes, which chemical family is used?
• Cartridge pre-filters installed ahead of a reverse osmosis unit serve what purpose?
• The Information Collection Rule requires large water systems to collect information to build a database to assist in the development of which regulations?
• Which device would best measure total suspended solids?
• What treatment chemical is corrosive, dense, and an oily liquid and is available in strengths of 62%, 78%, and 93%?
• The depth to which submerged plants will grow is primarily limited by ______
• Chlorine dioxide is how many times more powerful than chlorine?
• Excessive up-thrust on line shaft turbines is caused by
• ________ is often added to provide _______ and facilitate iron precipitation
• What is the most common unit of hardness?
• The process of removing organics from a water sample and concentrating them in a solvent suitable for injection into the ______ is called ______.
• In the Long-Term 2 Rule, which pairing correctly matches 'pack' to the concentration concept?
• Which genus has killed the most people because of its high mortality rate when contracted?
• Although _______ can be added to lime-soda ash rapid-mix basins, better results are usually obtained if they are added _______ in a separate rapid-mix basin.
• Jar tests are used to determine the dose of which material in water treatment?
• An organic contaminant from coagulants would most likely include which compound?
• Which term refers to the EPA program that surveys unregulated contaminants in drinking water?
• In the two-stage recarbonation process, the raw water pH is elevated to ____ or greater with lime; after that stage, carbon dioxide is added to lower the pH to ____
• The fluoride injection point should be as far away as possible from any _____.
• A special problem with granular activated carbon filters is the rapid growth of which microorganisms?
• In the Lead and Copper Rule, if a water system exceeds the 90th percentile for the lead action level, the system must also _______.
• The reason that a sample has a holding time is usually because the sample's ____ .
• In variable declining-rate filtration, what is placed in the effluent line of each filter to prevent excessive flow rates?
• What is the main purpose of presedimentation following screening?
• Which factor is most commonly cited as the benefit of pressure filtration for small water systems?
• When iron alone is treated using manganese greensand filters, the chlorine feed rate should be about ______.
• Caustic hypochlorite used in disinfection ranges in available chlorine from which percentage?
• Some systems using aeration towers are required to install air scrubbers. These scrubbers use _____.
• Rapid pressure changes in a distribution system can cause red water due to precipitation of which iron species?
• What are the potential hazards when handling activated carbon?
• Ammonia is fed at about what percent of the amount of chlorine used?
• What is the result of overexposure to hypochlorite compounds?
• Nitrite interferes with which chlorine residual measurement method?
• Which chemical is commonly added to provide alkalinity and facilitate precipitation of iron in water treatment?
• Stage 2 DBPR compliance is evaluated at each monitoring location using which metric?
• When using chlorine disinfectants, lower temperatures favor the formation of _______. Lower temperatures also show _______ to persist somewhat longer.
• What are some uses of synthetic organic chemicals (SOCs)?
• Which statement about pH and magnesium hydroxide precipitation is true?
• When temperature increases, the corrosion rate usually ________, and when the water is corrosive and the velocity increases, the corrosion rate ______?
• What is a potential concern when ozone is used as a primary disinfectant?
• What is the primary purpose of pressure aerators in water treatment?
• When ozone is used as a primary disinfectant, which byproducts may form that require monitoring?
• What is an operating factor that would affect floc formations?
• If THMs are still a problem after softening, and changing the disinfectant is not an option, what other treatment process can be used and what is its disadvantage?
• In calculating the C x T value, the contact time is extended to which point in the system?
• Chelation is a chemical treatment process used in water treatment to control what?
• Electrolytic flotation uses which gas mixture as a byproduct?
• What is skeletal fluorosis?
• Lubrication used on the bearings of line shaft turbines can be _____
• What is the Stage 1 Disinfectants and Disinfection Byproducts Rule maximum contaminant level for chlorite?
• Which regulatory rule explicitly includes monitoring for TTHM and HAA5 by Stage 1 DBPR?
• Turbidity is typically measured in what units?
• Ammonia is a dangerous gas and is readily detectable at concentrations of ______.
• What do the routine monitoring requirements of the Stage 1 DBPR include?
• Synthetic organic compounds would more likely contain _____ than natural organic compounds
• Which two test methods for coliform bacteria include a three-step process?
• Point-of-use activated carbon filters are most effective for removing which of the following?
• Which condition indicates poor floc formation?
• What is the correct order of parts that follows a pump for the listed components?
• Under the ______, nonuse for a long period of time may result in loss of water right by forfeiture or abandonment.
• Which pairing of membrane processes is effective for removing hardness from water?
• Which chemical looks like broken glass crystals?
• In the multiple-tube fermentation method, as presumptive positives are inoculated into Brilliant Green Broth (BGB), 0.1 mL of the presumptive broth is also transferred into which medium?
• Which statement best describes the factors that influence cleaning protocols for microfiltration membranes?
• How does cyanide affect the human body?
• In the simplest terms, what is hardness?
• If any stains or chemical residues remain after normal cleaning of labware, the glassware should be washed with a cleaning solution such as acid-dichromate.
• Phenolphthalein is colorless at low pH and pink or red at higher pH. How does it appear at pH below 8.3 and above 8.3?
• If there is no pretreatment, what membrane processes will remove dissolved organic matter?
• In water chemistry, what aspect of pH is of interest to chemists?
• After a routine sample tests positive for total coliforms, which analyses are required?
• In the presence-absence test, the presence of total coliforms is indicated by the medium turning yellow and the formation of what?
• Point-of-use activated carbon filters are most effective for removing which contaminant?
• What is used to coat the walls of sedimentation basins to rid the basin of slime growth?
• During greensand regeneration, continuous regeneration is typically used while the filter is offline.
• What is the maximum contaminant level (MCL) for arsenic in drinking water?
• What does the optimal pH establish when applying oxidation to iron and manganese?
• What is the purpose of turning off surface washers before the end of the backwash?
• Airline supplied air is not commonly used for emergency response because they are limited to only _______ ft.
• Lime-soda ash softening can reduce water hardness to approximately which range?
• The optimum fluoride level in drinking water, as recommended by the Department of Health and Human Services and the USEPA, is what?
• What should be done to a new shaft sleeve before it is put on a shaft if it uses an o-ring?
• Which statement correctly describes HOCl versus hypochlorite at low pH and low temperature?
• A gravity thickener would include which of the following components?
• When is the best time to start using a destratification equipment to overturn a lake?
• Which regulation requires performance goals for filters, data collection, and reporting exceptions for any filter not performing in accordance with the turbidity values stated in the rule?
• Caustic soda is commonly known as sodium hydroxide with formula NaOH. Which of the following options correctly pairs the name with its formula?
• Which two items are specifically targeted by LT1ESWTR turbidity performance standards?
• Mechanical mixers should never be used in conjunction with which component?
• What process is currently used for softening brackish water?
• In a two-stage recarbonation process, CO2 is added after lime to lower the pH to approximately which range?
• If dissolved oxygen increases and the pH and alkalinity do not increase, the corrosion rate will generally:
• Separate refrigerators should be used for the storage of which items because fumes of some chemicals may be harmful to the organisms?
• Which concept defines that the proportion by weight of elements in a compound is constant regardless of the method used to form the compound?
• Mass spectrometry identifies organic compounds by which characteristics?
• Monomedium filters are best suited for which filtration approach?
• Under current regulations, what type of samples must be collected from the source water supply?
• Titration is best described as a method used to determine the composition of a sample by incrementally adding a standard solution until what occurs?
• Which pairing of units correctly describes electrical energy and power?
• The rate of formation of _____ increases with increasing pH
• Breathing hydrogen sulfide gas at low concentrations can be fatal. Which combination is listed as fatal?
• Riparian rights are a common-law doctrine, which body of law are they part of?
• If raw water is pre-chlorinated, what color on the inside walls of filters and the filter media indicates the presence of both iron and manganese?
• In the lauryl tryptose broth test, which observation corresponds to a positive result?
• If a particular section of the distribution system suddenly has a drop in chlorine residual, what most likely has occurred?
• Which problem is commonly associated with hardness?
• What is the typical service life range for PDVF membranes in oxidants?
• To demonstrate 4-log inactivation of viruses, adequate C x T must be provided.
• Which is a limitation of softening?
• Because bromine is not as stable as chlorine, if it were used to treat public water supplies, how much more would be needed?
• What NSF/ANSI Standard covers coatings, construction materials, and components?
• After screening and presedimentation, there should be a significant reduction in which parameter?
• Which compound looks like broken glass crystals?
• What is the most common disinfection byproduct when chlorine is added to water containing natural and inorganic matter?
• In the lime-soda ash softening process, smaller plants find that ______ is less expensive to purchase; regardless of size, ______ needs to be mixed long enough because it dissolves slowly.
• In the Ground Water Rule for systems that disinfect, large systems are required to monitor ______ and small systems are required to monitor ______.
• Which parameter is used to quantify disinfection effectiveness as the product of concentration and time?
• Before installing a new shaft sleeve, it should be heated to _______.
• While converting carbonate back to bicarbonate, how does recarbonation affect the pH?
• Electrical conductivity meter readouts are in what units at what temperature?
• What type of pretreatment settling units can use coagulants because it has been showing to be very effective?
• What chemical is used for oxidizing iron and manganese that needs a reaction basin?
• When dewatering alum sludge using mechanical equipment, pretreatment is typically done with which device and feature?
• Which statement about pumps is false?
• What is the function of bases in a treatment plant?
• Which agency promulgated the Final Groundwater Rule?
• An electric current in a wire travels from end to end at _______. However, individual electrons within the wire move ______ and over ________.
• The abbreviation LT2 stands for which designation?
• Cryptosporidium and Giardia typically range in size from which of the following?
• Which type of aerators have riffle plates?
• Iron complexes with organic matter are anionic and are not removed by which type of exchange?
• What is titration?
• When natural gas and air are used to make CO2 for recarbonation, good ventilation is required because dangerous concentrations of which gas are produced?
• Microfiltration is considered to be intermediate between _______ based on pore size
• Which contaminants make up the Contaminant Candidate List (CCL)?
• Which unit correctly identifies the unit expressing electrical potential?
• What is another name for hydrochloric acid?
• If a UV reactor is operating outside of the validation limits by more than _____ of the water treated, it is considered off-specification.
• Hardness is generally expressed as the total concentration of which ions?
• The Long Term 2 Enhanced Surface Water Treatment Rule specifies that UV disinfection must provide at least what level of log removal for Cryptosporidium?
• If a water system exceeds the 90th percentile of either the lead or copper action levels, it must also assess _______.
• Which skin condition has lower resistance to electrical current flow?
• Which source water is most likely to contain iron and manganese?
• In a lead-acid battery, each of the battery cells produces an open circuit voltage of approximately ______
• Alternate description of glassy phosphates: Glassy phosphates are best described as which of the following?
• Interferences to aerometric chlorine residual measurement come from nitrite.
• Which substances serve as precursors to disinfection by-products when disinfectants are used?
• What type of pump has the ability to rotate its discharge 360 degrees?
• What is alkalinity?
• What does valence refer to in chemistry?
• What loads are applied to a pump's shaft?
• What are glassy phosphates?
• The flow through a sedimentation basin should not exceed
• What corrosion prevention chemical may actually cause tuberculation in iron pipe in the pH range of 7.5-9.0?
• What membrane process will remove hardness?
• During lime softening, the hardness-causing ions are transformed into which form as pH rises?
• What are the primary reasons that more small water systems are installing pressure filters?
• When analyzing samples for haloacetic acids 5 (HAA5), what is added to the sample container to quench more HAA5 formation?
• What is caustic alkalinity?
• How can the problem of poorly formed floc be solved?
• Which regulation protects public health by limiting levels of contamination in drinking water under the Safe Drinking Water Act?
• How often should amperage and voltage tests be performed on three-phase motors?
• What is produced after colloids have just become charge neutralized?
• What is CaCO3 known as?
• In the lime-soda ash softening process, coagulants are used to gather which substances into particles that settle readily?
• In a dual media filter, it is best to have ____ backwash rates because each type of media has a different ____.
• What is the primary purpose of routing power through transformers at a water treatment facility?
• In determining a safe following distance, you should primarily consider
• For conductivity measurements, which sampling option is correct?
• What pH is needed to form the magnesium hydroxide precipitate?
• One benefit of softening water
• Air binding is caused by pressure in the filters ______ than atmospheric pressure, and it can cause ______ flow.
• Which gas(es) does electrolytic flotation use?
• Chlorine dioxide can revert to chlorite and chlorate under which conditions?
• Jar tests are used to determine the powdered activated carbon dose. The glassware used need to be cleaned with _____ and rinsed with _____ water.
• To address iron problems when using resin exchange, which pre-treatment step is recommended?
• If algae or slime growth in sedimentation basins are a problem, drain the basin and apply a solution of ______ per liter of water using a brush to remove the growth.
• TOC removal requirements increase as alkalinity decreases. Which of the following best describes this relationship?
• Lime precipitation of noncarbonate hardness forms which noncarbonate salts?
• The best packing material for medium pressures and temperatures is which?
• In groundwater systems that disinfect and have deficiencies, 4-log inactivation of viruses must be demonstrated with adequate C x T.
• Which statement best describes the focus of the discussed rules in relation to drinking water?
• What are the principal precursors that react with disinfectants to produce disinfection by products?
• Which chemical lowers pH when added to water?
• Why can rapid sand filters handle higher filtration rates compared to slow sand filters?
• What corrosion prevention chemical may be the best overall treatment approach?
• Which option shows the correct pairing for caustic soda?
• What happens when high chlorine residual levels are applied to the softening units?
• The Filter Backwash Recycling Rule is intended to minimize health risks associated with recycling backwash water, particularly with respect to which pathogen?
• What will a coagulant aid not achieve from the following?
• What is the major reason that turbidity is undesirable?
• No preliminary contact or sedimentation chambers are necessary for which oxidation process?
• In groundwater, the total dissolved solids will change ______ and the dissolved oxygen will change _______, with the dissolved oxygen lowest most probably around ________.
• In dual-media filtration, if the ratio of anthracite size to sand size is close to 2, what is a likely outcome?
• The chlorine-measuring method that uses a chlorine gas-permeable membrane is the polarographic method.
• Bar or wire-mesh screens typically encounter the largest amount of debris in which season?
• Which combination is used to coat sedimentation basin walls to rid the basin of slime growth?
• Bicarbonate alkalinity is caused by which species?
• Bentonite clay improves coagulation by which mechanism?
• The slime layer prevents deposition of calcium carbonate. When the slime sloughs away, it carries away which substance and leaves the pipe surface bare?
• An advantage of using ozone treatment is....
• Which are usually the only cations present in water in significant concentration?
• PDVF membranes have excellent chemical resistance to which substance, and what is their typical service life?
• If too much aeration occurs after clarification and filtration, which process will most probably suffer?
• Which color range is used for color assessment by visual comparison with a color disk?
• Which particle size range is recommended for tracking by particle counters as a surrogate for Cryptosporidium?
• For manganese oxidation in surface water, which pH value would be sufficient to make the process effective?
• What is the MCL for radon in drinking water?
• Which alum sludge dewatering method can attain at least 20% solids by weight?
• When ozone reacts with organic contaminants to form organic acids, what may this eventually contribute to the distribution system?
• When can wearing gloves be a hazard?
• All sedimentation basins should be equipped with which of the following safety features?
• The LT2 rule requires a minimum chlorine residual at the entry to the distribution system. Which value is specified?
• Powdered Activated Carbon (PAC) is used in water treatment to achieve removal of contaminants primarily through which mechanism?
• Which softening process would probably not meet the Surface Water Treatment Rule requirements?
• Which water treatment chemicals lower the pH when added to water?
• In an electrolyte solution, a cation is attracted to which electrode?
• To preserve sediments from presedimentation for analysis, which sampling method is recommended?
• In order to achieve similar disinfection, combined chlorine residual must be greater than free chlorine by how many times under favorable conditions?
• The iodometric method is a variation of which method for dissolved oxygen determination?
• What are the effects of high iron and or manganese in water?
• Engineers usually design the height of a filter's backwash collection trough to allow for _____ bed expansion without loss of media into the troughs
• Emergency response at a water treatment facility generally means responding to a _______. This response is governed under the ______ and under _______.
• In the presumptive test, if gas is produced after either the 24-Hour or 48-Hour incubation period, the sample must undergo the confirmed test.
• What does total hardness represent?
• The oxidation of manganese in surface water is not effective until the pH goes to or surpasses which value?
• Actinomycetes are commonly linked to which water quality issue?
• The Surface Water Treatment Rule requires that the turbidity of the water entering the distribution system be equal to or less than ______ in at least ____ of measurements each month.
• Slow sand filters are cleaned by scraping the top ____ off the top of the sand filter.
• Which feed system reduces handling problems with powdered activated carbon?
• Which chemical is used to raise alkalinity but requires the most maintenance?
• The ripening of a filter after it backwashes depends on ________.
• What is the primary advantage of placing a properly sized anthracite coal layer over manganese greensand?
• The solubility of calcium carbonate decreases as temperature increases.
• Which statement describes how aluminum oxide is activated?
• In the Stage 2 Disinfectants and Disinfection Byproducts Rule, new sampling sites are based on what evaluation?
• The suction side of a pump's piping should be ______ pipe size ______ than the intake side of the pump.
• In microfiltration operation, stable flux is maintained while recovery is kept at or above what percentage?
• Which of the following is the correct alternative name for hydrochloric acid?
• The filtration ripening process is driven by which phenomenon?
• In the wellhead protection program, which technical step is essential?
• Under the Ground Water Rule, large systems disinfecting must monitor continuously while small systems must monitor daily.
• After water has been softened, it is close to pH 11; thus it needs to be stabilized by a process known as recarbonation. What small amount of hardness chemical is formed and what is precipitated in this process?
• If the pH of a water sample increases, the calcium carbonate level will ________, and as the temperature increases, the solubility of the calcium carbonate ________.
• In the context of softening, floc is often composed mainly of which precipitate?
• Which material would be best to use as caps on iron bolts so the caps become the sacrificial anodes and the iron bolts the protected cathodes?
• In a corroding pipe, the electrons released at the anode will combine with which species in the pipe at the cathode?
• The Radionuclides Rule added for the first time an MCL, for uranium of ______
• What is the chemical formula for hydrated ferric sulfate?
• Which membrane process combination removes hardness?
• When iron corrodes, it converts from which form?
• In the Long-Term 2 Rule, the bin scenario represents source water concentrations used to assess what?
• Which statement correctly pairs acidity types with pH ranges?
• There are two types of acidity: phenolphthalein acidity, which is prevalent ___________, and mineral acid acidity, which tends to be in the ________.
• Why is nitrate regulated?
• Which organism obtains energy for growth from the chemical reaction that spontaneously occurs between iron and manganese and dissolved oxygen?
• A low-cost radioactive scan is first done to determine if the level of radioactivity is high enough to progress to further analyses. The level of radioactivity that would call for further analysis is normally the ______ for ______ or _________ but can be varied by the particular state drinking water agency.
• Which phrase best describes the crystals that resemble broken glass in certain compounds?
• In the multiple-tube fermentation method, as presumptive positives are inoculated into BGB, 0.1 mL of presumptive broth is also transferred into which broth?
• To eliminate hydrogen sulfide (H2S), the pH of the water should be lowered to _______ or less before beginning aeration.
• Long-range planning for a water system's source of supply should be approximately which range?
• Alkalinity definition and units
• In the EC-MUG test, if the tube _______, it is positive for E. Coli.
• What is the best-known solution for excessive algae growth in a presedimentation impoundment?
• To ensure adequate contact time before chlorine addition, PAC should have at least ______ minutes.
• Under the Surface Water Treatment Rule, the turbidity entering the distribution system must not exceed _____.
• What does the Unregulated Contaminant Monitoring Regulation provide the EPA?
• Garnet sand is used at the bottom medium in multimedia filters. What characteristics does garnet sand have compared to the other sand in the filter?
• What happens when the brine solution is fed into the resin?
• If a water system exceeds the action level for lead and copper, it must measure other contaminants as well. What parameter must be measured in the field?
• In lime-soda ash softening, which compound is formed by reaction of lime with carbonate hardness?
• Which type of sample is specifically excluded from mailing to a laboratory for transport?
• Iron bacteria, such as which organism, cause red water, tastes and odors, clogged pipes, and pump failure?
• Stage 2 Disinfectants and Disinfection Byproducts Rule uses sampling sites based on what evaluation approach?
• Unlike reverse osmosis and nanofiltration, the recovery of the microfiltration process is not limited by the formation of _____ or the precipitation of _____.
• Methyl orange used as an indicator in titrations is ______ on the alkaline side and _______ on the acid side.
• Which statement about the lime-soda ash process is true?
• Which of the following salts is not typically a hardness-causing salt?
• After the Long-Term 2 Surface Water Treatment Rule testing, a system is put into a ________, which are ______ concentrations in the source water for the theoretical potential for contamination.
• Where is nitric acid most commonly used within a water treatment facility?
• Under the Stage 1 Disinfectants and Disinfection Byproducts Rule, which compound has an MCL of 1.0 mg/L?
• Chelation controls _______, and sequestration controls _______.
• Which statement about the lime-soda ash process characteristics is correct?
• During manganese greensand bed regeneration, which chemical is used to regenerate the media?
• What is a disadvantage of using chlorine dioxide in water treatment?
• What is under the state-level aquifer protection standard setting?
• The best way to remove H2S is by scrubbing at about _______ by bubbling CO2 through the water before aeration to reduce the pH
• A hazardous measuring device would most likely be _______
• In coagulation, once zeta potential forces are reduced below the ______________, the particles in suspension will start to coalesce?
• The Information Collection Rule is designed to support the development of which types of regulations?
• One key element of LT2 is to use monitoring results to classify surface water sources into USEPA-defined risk levels called bins. How many bins are defined?
• A condenser will allow which type of current to flow through it, but block the other? One use is to suppress voltage surges.
• What is the chemical formula corresponding to caustic soda?
• Under LT2, which three parameters were added for testing?
• Scale is formed from the combination of which?
• Even after equipment is locked out and tagged, why might it still be unsafe to repair?
• This parameter is used to determine if the Disinfectants and Disinfection Byproducts Rule is in compliance.
• If a water system exceeds the action level for lead and copper, which parameter must be measured in the laboratory?
• Chlorine dioxide can revert to chlorite and chlorate under which conditions?
• In HPC testing, where are the diluted water samples placed and how long are they incubated?
• Powdered activated carbon dosing: which feed system reduces handling problems?
• Hardness has any unwanted health effects?
• Under the Interim Enhanced Surface Water Treatment Rule, what Giardia log reduction credit is given for conventional treatment with disinfection credits?
• As the TOC increases, the TOC percentage removal required from a source water supply _______.
• Under LT2, UV disinfection is specified to provide at least a log removal/inactivation for which organism?
• The ____ process is used in the water industry primarily for the removal of ______.
• Permanganate reactions are largely dependent on ________.
• Why is ozone treatment often followed by granular activated carbon, which removes assimilated organic carbon caused by the action of the ozone treatment?
• Which agencies are recommended to set the optimum fluoride level in drinking water?
• Cleaning protocols for microfiltration membranes vary according to the membrane tolerance to changes in which parameter and resistance to which chemical?
• Large bubble diffusers can be cleaned with which method?
• What is the mechanism by which potassium permanganate works when used to control algae?
• Which hazard pair is most associated with handling activated carbon?
• Under LT2, surface water sources are classified into how many USEPA-defined risk levels called bins?
• Where in the treatment plant is nitric acid most commonly used?
• Which solvent is used to clean an old bearing?
• Which device best measures total suspended solids?
• The dosage of lime and soda ash at a softening plant is based on which of the following alkalinities?
• Actinomycetes are a group of organisms usually associated with tastes and odors. This group has the characteristics of _______.
• During HAA5 analysis, which chemical is used to quench further HAA5 formation?
• Because the gas generated from _______ is pure CO2, the pipes from the diffusers can be _________ than those needed for CO2 generated on site by combustion.
• Beneath the slime layer of certain iron bacteria in a pipe, what is produced that reduces pH and speeds up the corrosion rate?
• Which filter has an unstratified media distribution?
• Groundwater systems at high risk for fecal contamination must provide a 4.0-log inactivation of viruses.
• Small and medium sized utilities are deemed to have optimal corrosion control if they meet lead and copper levels for how many consecutive sampling periods?
• Which factor will cause problems for chlorination?
• Which statement best describes the focus of the primary drinking water regulations?
• Chlorinating before a microstrainer may cause a sticky, jelly-like coating to form on the microstrainer. What is present in the water that causes this problem?
• If dissolved oxygen increases, the corrosion rate changes as well as the effect of increasing pH and alkalinity on corrosion rate.
• A metal rod should be used to probe the filter on a grid system to locate and record the depth to gravel. At a minimum, how often should this be done?
• What are hearing protection devices given to evaluate their effectiveness?
• Water becomes capable of _______ iron and manganese when the oxygen levels ________.
• What type of pretreatment must be cleaned manually when the amount of debris is relatively small?
• What pH level is required to precipitate magnesium hydroxide?
• Which factors contribute to the difficulty of inactivating all microorganisms with a single treatment method?
• What is the CT value?
• Which regulation addresses backwash water recycling in filtration plants?
• What is the most common radionuclide anion?
• Carbonate hardness relative to total hardness
• How is magnesium noncarbonate hardness removed?
• Which protozoan parasite is a key target in modern drinking water treatment due to resistance to disinfection methods?
• What instrument is used to measure the depth to gravel in a filter bed?
• ______ and ______ should not be stored in the same refrigerator.
• If PAC does not remove tastes and odors, what is a likely explanation?
• Which results are used to develop the Langelier saturation index?
• Which arrangement describes lamella plate flow?
• Gas chromatography-mass spectrometry is used to determine which category of compounds in a sample?
• In greensand filtration, CR is usually used when which contaminant is mostly removed?
• Which chemical is used to raise alkalinity in water treatment?
• The Langelier Saturation Index is used to assess the tendency of water to precipitate or dissolve calcium carbonate.
• What is an ion?
• To address algae growth in sedimentation basins, which combination is applied per liter when drains are used?
• Why are cold-weather conditions an added hazard when working around water?
• Which colors are not assigned numerical color units?
• Circuit breakers, compared to _______, have a much _______. This means that they are capable of interrupting the flow of considerably _____ than could be interrupted by _______.
• What is the approximate open-circuit voltage per cell in a lead-acid battery?
• Which organism was introduced to the United States from Southeast Asia and has become a significant pest in almost every river system?
• What will most likely exhaust GAC first?
• Which combination describes a low-cost PAC feed method suitable for secondary treatment?
• In the chemical precipitation process, the hardness causing ions are converted from [blank] forms. Calcium and magnesium become [blank] as the pH increases.
• What material is commonly used to cap greensand filters to improve performance?
• Which compound is commonly used to prevent encrustation by sequestering metal ions?
• The platinum-cobalt method measures which property in water?
• Which year range best represents a long-range planning horizon for a water system's source of supply?
• When chlorine dioxide is generated on site, a small amount of which species can be formed?
• A low-cost method of feeding PAC is to use a _____ where precise feed in ____
• How can an operator accept responsibility for an active role in the safety program?
• The excess lime-softening process is used so that which compound will precipitate out of the water?
• Hypochlorous acid is favored over hypochlorite ion when the pH is _____ and the temperature is ________.
• In manganese greensand filtration, what is the typical layer above greensand?
• What is the percentage of copper in copper sulfate (CuSO4)?
• Destratification is most effective when the lake has a stable layer of warm surface water over cooler bottom water.
• Water that is highly colored with organic material requires a _______ pH for coagulation; therefore, ________ before _________ may be necessary.
• Electric energy is usually expressed in _______, and power is expressed in ______
• It is recommended that the free chlorine residual at a customer's tap should be at least ________.
• Which statement describes a common natural form of manganese (Mn) in soils and is not MnO?
• Before making corrosion control changes, with which state authority should utilities coordinate first?
• In a concentration cell corrosion, what gas is produced?
• The optimum pH for the removal of excess fluoride by activated alumina is _____.
• Which regulation includes Giardia reduction credits for conventional treatment with disinfection?
• For source water at or below 10 NTU, the sedimentation effluent should meet which turbidity criterion for 95% of the time?
• If TOC removal percentages cannot be met, a utility can comply with the EPA rule by removing at least ______ of _______, as CaCO3, measured monthly and calculated quarterly as an annual running average.
• Synthetic organic compounds are more likely to contain which halogen than natural organic compounds?
• In viscosity testing, which unit is commonly used to express viscosity?
• In the brine regeneration process, which cations are exchanged on the resin by sodium?
• The precipitative softening process uses which mechanism to render calcium and magnesium insoluble?
• A special problem with granular activated carbon filters is the rapid growth of which microorganisms?
• Which parameter most strongly influences permanganate reactions in water treatment?
• What should you base a safe stopping distance behind the vehicle in front of you on?
• Under USEPA radionuclide sampling frequency for entry point testing, if results are greater than or equal to one-half the MCL and less than the MCL, sampling frequency is every how many years?
• At a softening plant, the most severe carryover of sludge in a sedimentation basin occurs when which condition?
• Which statement best describes circuit breakers in relation to switches?
• Besides using carbon dioxide, encrustation can also be prevented by adding ______
• In the described extraction method, the analytes are concentrated for injection into which instrument?
• In HPC testing, which plating incubation duration applies for plate-count agar?
• Before installing casing wear rings, what preparation step is recommended?
• If hardness leakage is excessive after regeneration, which action is most appropriate?
• Chlorite is regulated under the _______ and has maximum contaminant level of ______.
• The final RCTR requires which entity to notify the public if a test exceeds the MCL for E. coli in drinking water?
• Driven wells are practical only when the water-bearing formations are relatively close to the surface and no contaminants exist in the soil. Which statement best describes this condition?
• Which action is NOT recommended when working around machinery with moving parts?
• In reporting the water quality, turbidity is expressed in which unit?
• What is a limitation of the ion exchange softening process?
• Which oxidant used for iron and manganese will react with hydrogen sulfide and will not form trihalomethanes?
• The precipitative softening process uses _____ that render _______ calcium and magnesium ______
• Which process is used in the water industry primarily for the removal of organic substances?
• Which two hardness-forming cations are most commonly present in significant concentrations?
• In the lauryl tryptose broth test, which combination describes the bacteria associated with a positive result?
• The DBPR focuses on which group of contaminants?
• Lime slakers should be equipped with a _______ that will stop the lime feed before _______.
• Adjustments to the carbon dioxide dosage in recarbonation should be based on both the Langelier saturation index and results of coupon testing.
• Which radon removal method is most effective considering cost and footprint?
• Sodium hypochlorite is usually purchased at 12% to 12.5% and is then distributed down to a more stable percentage of ______.
• Slow sand filtration cleaning involves removing how many inches from the top of the filter?
• The flocculation and settling of calcium carbonate and magnesium hydroxide precipitates occur more quickly in the presence of what?
• A calcium sulfate molecule would be considered a dissolved solid.
• Dissolved air flotation has achieved a ______ removal of cryptosporidium, which compares to a removal rate of less than 0.5 log using conventional sedimentation.
• The most common higher-rate filter media consists of the following (bottom to top)
• The 1996 Risk Management Rule was issued to protect public health and safety for which group?
• What should the operator do for best results in a plant with six flocculators?
• For nomographic determination of CO2 in water, which additional properties must be known?
• Which statement is true about the Saybolt Universal Seconds (SUS) unit?
• What is the main, easiest way to identify a confined space?
• Microfiltration membranes made from PDVF have excellent chemical resistance to which substance, and what is their typical service life?
• Carbonate alkalinity is caused by which ion?
• Increasing which factors together will decrease corrosion rate?
• The Lead and Copper Rule is different from the other rules in that it deals with ______ to determine compliance.
• How is aluminum oxide activated?
• What indicates whether the small amount of fluid in the tip of a pipette that remains after it has drained should be blown out?
• Which method is the least reliable for detecting hydrogen sulfide?
• What is a common disadvantage of using caustic soda to soften hard water?
• What was the primary concern for why the Final Groundwater Rule was promulgated?
• What membrane configurations are currently available and used in drinking water treatment plants?
• In dual media filtration, if the ratio of anthracite size to sand size is close to 2, which outcomes may occur?
• Which instrument has a fixed light source and provides a qualitative measurement but cannot detect particles that do not scatter light?
• What acid is more corrosive when it is diluted?
• If a routine or repeat sample tests positive for total coliforms, it must also be analyzed for _______.
• In the oxidation of iron and manganese, the pH must be adjusted to an optimal level. What must be determined to accomplish the optimal pH?
• Which type of process control uses a mode where the output is directly proportional to the deviation from the set point?
• A water that does not form scale or corrosive is stable; this condition is called what?
• In mass spectrometry identification, the key signature used is which?
• In a buttress dam, the impounded water's weight is used to resist which forces?
• Which of the following correctly reflects the health concern associated with turbidity as described in the material?
• In a filtration system, adding an anthracite coal layer over greensand primarily improves which performance aspect?
• Which temperature-time combination is used to heat a shaft sleeve prior to installation?
• Backwash bed expansion to prevent media loss is designed to reach what percentage?
• Which action best reduces siltation in a reservoir?
• Which method is listed as another approach for the modified Winkler method?
• The specific ultraviolet absorbance (SUVA) is calculated using the absorbance of UV light at 254 nm ______ the concentration of _______
• Which material is commonly used as a sacrificial anode to protect iron components from corrosion?
• The current travels end-to-end at high speeds; electrons move relatively slow over short distances. Which option correctly reflects this statement?
• Which of the following is not a part of a bearing?
• The ideal alkalinity for manganese greensand filters for the removal of iron and manganese is _______ as CaCO3.
• To provide adequate protection, what should the noise reduction rating (NRR) of the hearing protection device be?
• In nanofiltration and reverse osmosis, membrane compaction rates increase when membranes are operated at which conditions?
• Molecular weight is expressed in which units?
• Why do some water treatment plants avoid addressing iron, manganese, arsenic, and disinfection byproducts in their treatment operations?
• The regulatory framework that includes a limit for chlorite is part of which EPA rule?
• Which statement about carbonate hardness is correct?
• Which coliform test methods have three distinct steps: presumptive, confirmed, and completed?
• For conductivity sampling, which statement is correct?
• Mineral acids are measured by titration to a pH of 4.3 using which indicator?
• In open filters, which pairing of media is associated with superior organics removal?
• In 2003, the USEPA revised the drinking water standard for arsenic from which range to which range?
• What type of aerators have riffle plates?
• The best packing for medium pressures and temperatures is ______
• To prevent algae growth, which action is most appropriate?
• Equivalent weight is defined as the weight that will react with, displace, or is equivalent to one gram of hydrogen.
• Which skin condition provides more resistance to electrical current flow?
• Why is polyphosphate added to softening process water?
• Chelation is a chemical treatment process used in water treatment to control which condition?
• Chloramines will be used when tastes and odors are a problem, particularly when the source water contains
• What type of automation control would work best if the chlorine demand varies but the flow is constant?
• How often are the maximum daily temperatures determined to establish the optimal fluoride levels for any particular state?