Chemical Additions Flashcards by Rene Lichtl

The two most important factors impacting the effectiveness of chlorination are?

a. pH of the water and the content of foreign substance in the water.
b. concentration of chlorine and the content of foreign substance in the water.
c. concentration of chlorine and contact time.
d. pH and temperature of water.

c. concentration of chlorine and contact time.

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The treatment process that controls corrosion or scaling

is known as?

a. chemical control.
b. stabilization.
c. passivation.
d. corrosion kinetics.

a. Stabilization

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Permanganate reactions are highly dependent upon?

a. organics in the water.
b. pH.
c. temperature.
d. alkalinity.

b. pH

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It is hardest to kill the organism that causes which one of the following illnesses?

a. Cholera.
b. Typhoid.
c. Cryptosporidiosis
d. Infectious hepatitis

c. Cryptosporidiosis

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Disinfection of water wells with free chlorine requires

exposure for _______ at a concentration of ______.

a. 6 to 12 hours; 25 mg/L
b. 12 to 24 hours; 25 mg/L
c. 12 to 24 hours; 50 mg/L
d. 24 to 48 hours; 100 mg/L

c. - 12 to 24 hours

50 mg/L

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Which index determines the calcium carbonate deposition property of water by calculating the saturation pH, where a negative value indicates corrosive water and a positive value inicates depositing water?

a. Baylis curve
b. Langelier saturation index
c. Marble test
d. Ryzner index

b. Langelier Saturation Index

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The advantage to using the oxidant ozone is that it ______.

a. is easily generated using relatively little energy.
b. is easily fed into the treatment process.
c. is non-corrosive.
d. has little pH effect.

d. has little pH effect.

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Pretreatment with chlorine is being eliminated at many water treatment plants because it has been shown to _______.

a. react with floc and not much with organics, pathogens, or algae, thus it is a waste of resources and money.
b. react with organics almost exclusively and not much with pathogens or algae, thus it is a waste of resources and money.
c. sometimes produce disinfection by-products known to be carcinogenic.
d. react by as much as 95% of its concentration with concrete walls and metal structures before oxidizing pathogens, organics, and algae.

c. sometimes produce disinfection by-products known

to be carcinogenic.

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CTs are based on?

a. concentration of chlorine, contact time, and pH.
b. concentration of chlorine, contact time, pH, and temperature
c. concentration of chlorine, contact time, pH, and water impurities.
d. concentration of chlorine, contact time, alkalinity, pH, and temperature.

b. concentration of chlorine, contact time, pH, and temperature.

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If the natural fluoride content of the raw water is variable, the concentration of the raw water should be measured?

a. every 8 hours.
b. every 12 hours.
c. evrey day.
d. continuously

c. every day

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Which is the primary drawback for facilities that use Ultraviolet light to disinfect water?

a. It does not inactivate all microorgnisms.
b. It has the potential to produce trihalomethanes.
c. Dissolved colloids can shield microorganisms from the UV light.
d. There is potential for the light bulbs to be coated with light-obscuring material, preventing the UV light from killing microorganisms

d. There is a potential for the light bulbs to be coated with light-obscuring material, preventing the UV light from killing microorganisms.

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Potassium Permanganate is most effective in?

a. color removal.
b. control of biological growth.
c. control of trihalomethanes formation potential.
d. removing iron.

d. removing iron.

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Chlorine is advantageous over chloramines in that chlorine?

a. is a much stronger oxidant.
b. has a long history of use.
c. has simple feeding.
d. has a persistent residual.

a. is a much stronger Oxident.

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Which oxident has the potential of producing ClO₃

by-products?

a. Chlorine dioxide
b. Chlorine
c. Chloramines
d. Calcium hypochlorite

a. Chlorine Dioxide

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How thick should the layer of sodium fluoride crystals be maintained in a saturator tank for flows of less than 100gpm?

a. 6 inches
b. 10 inches
c. 1 foot
d. 2 feet

a. 6 inches

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Which disinfectant would work best against

cryptosporidium?

a. Ozone
b. Dichloramine
c. Chlorine dioxide
d. Hypochlorous acid

a. Ozone

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Which chemical oxidant would be best to use for controlling

trihalomethanes formation potential?

a. Chloramines
b. Chlorine dioxide
c. Oxygen
d. Potassium permanganate

d. Potassium permanganate

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Ozone generators ________.

a. must be supplied with extremely dry air.
b. are usually plate type generators for large water plants.
c. will produce about 12% ozone by weight when supplied with air.
d. will produce about 20% ozone by weight when supplied with oxygen only.

a. must be supplied with extremely dry air.

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A conventional treatment plant has raw water with high organic content. Respectively, name the most probable oxidants and disinfectants to use, if the plant applies oxidants/disinfectants at the (1) rapid mix chamber, (2) prefilter, at the (3) clearwell, and (4) clearwell effluent, and a long lasting residual is required.

a. (1)chlorine; (2)sodium hypochlorite; (3)sodium hypochlorite; (4)chlorine
b. (1)chloramines; (2)chlorine; (3)chlorine; (4)chloramines
c. (1)potassium permanganate; (2)chlorine; (3)chlorine; (4)chloramines
d. (1)hydrogen peroxide; (2)chloramines; (3)chloramines; (4)chloramines

(1) Rapid mix chamber: Potassium Permanganate
(2) Prefilter: Chlorine
(3) Clearwell: Chlorine
(4) Clearwell effluent: Chloramines

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If air is used to generate ozone, which percentage of the air is usually converted to ozone?

a. 1 to 3%
b. 4%
c. 5 to 6%
d. 9 to 11%

a. 1 to 3%

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Which is the principal scale-forming substance in water?

a. Zinc orthophosphate
b. Sodium carbonate
c. Calcium
d. Calcium carbonate

d. Calcium carbonate

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Which oxidant should be fed as early as possible in the treatment process to allow for complete reaction before it enters the distribution system?

a. Ozone
b. Chlorine dioxide
c. Chloramines
d. Potassium permanganate

d. Potassium permanganate

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The flexible copper tubing that connects a 150-lb chlorine cylinder to a manifold should be rated at ________.

a. 100 psi
b. 150 psi
c. 250 psi
d. 500 psi

d. 500 psi

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The buildup of corrosion products is a process known as ________.

a. deposition.
b. electrochemical deposition.
c. physiochemical deposition.
d. tuberculation.

d. tuberculation.

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Potassium permanganate \_\_\_\_\_\_\_\_\_\_. a. usually has a dosage range from 10 to 15 mg/L. b. oxidizes to manganese dioxide, which can give the water a purple color. c. should be fed before chlorine. d. should be used with powdered activated carbon (PAC).

c. should be fed before chlorine.

Low values for which water characteristic may require the addition of lime, caustic soda, or sodium bicarbonate? a. Turbidity b. Water temperature c. pH d. Alkalinity

d. Alkalinity

Which chemical could cause pink water problems? a. Chloramines b. Potassium permanganate c. Bromine d. Iodine

b. Potassium permanganate

The most frequent in situ well treatment is the application of a(n) \_\_\_\_\_\_\_\_\_. a. chemical to adjust pH of well water that is either too acidic or too alkaline. b. phosphate inhibitor to prevent well pump corrosion. c. oxidant to reduce iron bacteria. d. coagulant for high turbidity well water.

c. oxident to reduce iron bacteria.

Which chemical is slaked lime? a. Ca(OH)₂ b. Ca(HCO₃)₂ c. CaCO₃ d. Ca(H₂O)₂

a. Ca(OH)₂

Calcium sulfate (CaSO₄) is also known as \_\_\_\_\_\_\_\_\_. a. gypsum. b. limestone. c. dolomite. d. talc.

a. gypsum.

Which color does the oxidant potassium permanganate turn at its end point? a. Reddish-brown b. Red c. Pink d. Yellow

d. Yellow

The simplest chlorine gas feeder for controlling chlorine gas flow is \_\_\_\_\_\_\_\_\_. a. constant differential pressure. b. variable defferential pressure. c. sonic flow. d. induction mixer.

c. sonic flow.

Which is usually used to disinfect the gravel packing of a groundwater well? a. Chlorine dioxide b. Powder of calcium hypochlorite tablet c. Sodium hypochlorite d. chloramines

b. Powder of calcium hypochlorite tablet

Which is true regarding chlorine one-ton containers? a. Full one-ton containers weigh at least 4,500 pounds b. Full one-ton containers weigh about 2,750 pounds c. The chlorine containers have three fusible plugs on the valve end and two on the opposite end d. One-ton containers are equipped with two valves, one for liquid and one for gas

d. One-ton containers are equipped with two valves, one for liquid and one for gas

Teeth are likely to become pitted when the fluoride concentration in drinking water goes above which amount? a. 3 mg/L b. 4 mg/L c. 5 mg/L d. 6 mg/L

b. 4 mg/L

How many pounds of ammonia are contained in a full 1-ton cylinder? a. 800 b. 1,000 c. 1,500 d. 2,000

a. 800 lbs

High pH favors the formation of \_\_\_\_\_\_\_\_\_. a. haloacetic acids. b. total trihalomethanes. c. both haloacetic acids and total trihalomethanes. d. neither haloacetic acids nor total trihalomethanes.

b. total trihalomethanes.

How often is it recommended to check the fluoride feed system? a. At least once every 24 hours b. Every 12 hours c. Every 8 hours d. Every hour

d. Every hour

Low pH favors the formation of \_\_\_\_\_\_\_\_\_. a. haloacetic acids. b. total trihalomethanes. c. both haloacetic acids and total trihalomethanes. d. neither haloacetic acids or total trihalomethanes.

a. haloacetic acids.

Dental fluorosis is \_\_\_\_\_\_\_\_\_. a. dental cavities. b. mottling of the teeth. c. fluoride dental rinse. d. coating of fluoride on the enamel of teeth.

b. mottling of the teeth.

One volume of liquid chlorine will expand to approximately how many volumes of gas? a. 440 b. 460 c. 480 d. 484

b. 460

In general, how long does ozone last when it is dissolved in water for disinfection purposes? a. A few seconds to a few minutes b. 5 to 10 minutes c. 10 to 15 minutes d. 15 to 30 minutes

a. A few seconds to a few minutes

Sodium fluoride \_\_\_\_\_\_\_\_\_\_. a. was once called silly acid. b. is a straw yellow color. c. has a solution pH of about 1.0 pH units. d. is odorless.

d. is odorless.

Which does the saturation point of calcium carbonate primarily depend upon? a. pH b. Temperature c. Concentration of calcium d. TDS

a. pH

Which will increase pH, hardness, and alkalinity? a. Sodium hydroxide b. Zinc orthophosphate c. Lime d. sodium zinc phosphate

c. Lime

How often should the fluoride concentration of treated water be measured? a. Every 8 hours b. Every 12 hours c. Every day d. Continuously

c. Every day

Which is the pH of a saturated solution of sodium fluoride? a. 6.2 b. 7.0 c. 7.8 d. 8.0 to 8.4

b. 7.0

Which is the most effective wavelength when using ultraviolet light for disinfection? a. 2,235 angstroms b. 2,650 angstroms c. 2,875 angstroms d. 2,965 angstroms

b. 2,650 angstroms

Which type of chlorine gas feeder is most commonly used? a. Pressure b. Combination c. Vacuum d. Combination pressure and vacuum

c. Vacuum

Which substance is a depolarizer? a. Carbonates b. Nitrates c. Polyphosphates d. Silicates

b. Nitrates

Which composes the majority of scale in pipe? a. Ca(HCO₃)₂ b. CaCO₃ c. MgCO₃ d. CaSO₄

b. CaCO₃

The specific gravity standard for gases is \_\_\_\_\_\_\_\_. a. water vapor at 100^oC. b. air. c. oxygen. d. nitrogen.

b. air.

Which chemical oxidant is most effective in reducing the concentration of tast-and-odor compounds caused by actinomycetes species? a. Chloramines b. Peroxone c. Chloride dioxide d. Potassium permangante

b. Peroxone

Which oxidant is a bluish toxic gas with a pungent odor? a. Bromine b. Iodine c. Ozone d. Potassium permanganate

c. Ozone

Past the breakpoint chlorination point, which percentage of the chlorine residual should be free chlorine? a. 75 to 85% b. 85 to 90% c. 90 to 95% d. 100%

b. 85 to 90%

Sodium hypochlorite has a pH range of \_\_\_\_\_\_\_\_\_. a. 6.0 to 7.5 pH units. b. 7.5 to 8.5 pH units. c. 8.5 to 9.5 pH units. d. 9.0 to 11.0 pH units.

d. 9.0 to 11.0 pH units.

Where should the fluoride injection point be located? a. Right after flocculation b. After sedimentation, but before lime softening c. Before filtration d. After water has received complete treatment

d. After water has receive complete treatment

The corrosion process can be accelerated by certain bacterial organisms because they produce which chemical? a. N₂ b. CO₂ c. MgCO₃ d. CaCO₃

b. CO₂

Which chemical would be best to use for corrosion inhibition if the water is very low in alkalinity and calcium concentration? a. Sodium carbonate b. Sodium bicarbonate c. Sodium hydroxide d. Polyphosphates

d. Polyphosphates

If the temperature drops below _____ a 50% solution of caustic soda will begin to crystallize. a. 44^oF b. 48^oF c. 54^oF d. 58^oF

c. 54^oF

When chlorine has destroye all reducing compounds, any chlorine remaining will react with \_\_\_\_\_\_\_\_. a. nitrite and form chloramines. b. nitrates and form chloramines. c. ammonia and form chloramines. d. organics and form aromatics.

c. ammonia and form chloramines.

Low values for which water characteristic usually cause poor coagulation, flocculation, and settling characteristics? a. Water temperature b. Turbidity c. Alkalinity d. pH

a. Water temperature

Polyphosphates would most likely give the best results at \_\_\_\_\_\_\_\_. a. high alkalinity levels. b. high water temperatures. c. low pH values. d. high pH values.

c. low pH values.

Which is the most effective disinfectant for inactivating bacteria? a. Hypochorite ion b. Hypochlorous acid c. Chloramines d. Bromine

b. Hypochlorous acid

Which chemical oxidant is the weakest? a. Potassium permanganate b. Ozone c. Chloramines d. Chlorine dioxide

c. Chloramines

Which is the density of liquid chlorine? a. 1.25 b. 1.50 c. 2.50 d. 3.50

b. 1.50

Which device(s) uniformly disperse(s) the chlorine solution into the main flow of water? a. Injectors b. Pressure regulating valve c. diffusers d. Effluent nozzles

c. diffusers

The pressure in a chlorine cylinder depends on the \_\_\_\_\_\_. a. amount of chlorine in the cylinder. b. temperature of the chlorine liquid. c. vacuum placed on the regulator. d. amount of gas being withdrawn.

b. temperature of the chlorine liquid.

Sodium bicarbonate needs to be stored in a cool, dry place because it decomposes rapidly as the temperature nears \_\_\_\_\_\_\_\_. a. 80^oF b. 100^oF c. 115^oF d. 125^oF

b. 100^oF

In the breakpoint chlorination curve, in which zone do inorganic chlorine demand-causing compounds consume free chlorine? a. Zone 1 b. Zone 2 c. Zone 3 d. Zone 4

a. Zone 1

Which is the optimal pH level for sulfate-forming reactions with chlorine? a. 6 b. 8 c. 9 d. 11

a. 6

Liquid chlorine is which color? a. Yellow b. Dark green c. Amber d. Light brown

c. Amber

When chlorine gas is under a vacuum reliquefaction will not occur until the temperature drops below \_\_\_\_\_\_\_\_. a. -20^oF. b. -30^oF. c. -38^oF. d. -48^oF.

b. -30^oF.

Which method can be used to control scale and corrosion? a. Softening b. pH and alkalinity adjustment with lime. c. Sequestering d. Chelation

b. pH and alkalinity adjustment with lime.

Which is the chemical formula for hydrated lime? a. CaO b. CaCO₃ c. Ca(OH)₂ d. CaMg(CO₃)₂

c. Ca(OH)₂

Once iron bacteria become established in a well, shock chlorination will be required. The shock treatment is required \_\_\_\_\_\_\_\_\_\_. ## Footnote a. at increasingly shorter intervals. b. at increasingly longer intervals. c. at very regular intervals. d. sporadically, depending on many physical water quality factors and specifically on pumping rates.

a. at increasingly shorter intervals.

Which should accompany shock treatment to maximize its effectiveness for a well that has been fouled by iron bacteria? a. Constant addition of more chlorine as it is consumed, as determined by chlorine wet tests. b. Air surging, valved surge blocks, or jetting c. Slow addition of surfactants d. 1 to 5% acid solution added with the chlorine

b. Air surging, valved surge blocks, or jetting

Which should the concentration of chlorine be just before the pump is starte (for surging and moving the disinfectant into the aquifer and well) in order to sufficiently disinfect a public water supply well? ## Footnote a. 10 mg/L b. 25 mg/L c. 50 mg/L d. 100 mg/L

c. 50 mg/L

Which compound will decrease in solubility as the temperature rises? a. Slaked lime b. Calcium carbonate c. Magnesium hydroxide d. Magnesium oxalate

a. Slaked lime

Which is the most probable solution if nitrifying bacteria are increasing the demand for the disinfectant being used? a. Optimize nutrient control at the water plant b. Superchlorinate reservoirs and storage tanks c. Increase detention time in reservoirs and the distribution system d. Use powdered activated carbon in the filters

b. Superchlorinate reservoirs and storage tanks

When air is used to generate ozone, an air dryer should be used to reduce the production of \_\_\_\_\_\_\_\_\_. a. nitrous oxides. b. hydrogen gas (H₂). c. water. d. ammonia (NH₃).

a. nitrous oxides.

Which shows the correct relative strengths fo chlorine species as disinfectant? a. HOCl \> OCl \> NH₂Cl \> HCl b. OCl \> HOCl \> NH₂Cl \> HCl c. NH₂Cl \> HCl \> HOCl \> OCl d. HCl \> HOCl \> OCl \> NH₂Cl

a. HOCl \> OCl \> NH₂Cl \> HCl

When ultraviolet radiation is used to inactivate microorganisms, which are the optimum wavelengths? a. 100 to 200 nanometers (nm) b. 250 to 265 nm c. 330 to 360 nm d. 400 to 500 nm

b. 250 to 265 nm

Regarding the breakpoint chlorination curve, the chlorine dosage must go beyond which point in the curve to eliminate tastes and odors? a. Point 2 b. Point 3 c. Point 4 d. point 5

c. Point 4

Which chemical will decriase alkalinity? a. Silicates b. Carbon dioxide c. Sodium hydroxide d. Sodium bicarbonate

b. Carbon dioxide

Which oxidant would cause the most corrosion and scaling problems? a. Ozone b. Chlorine dioxide c. Chloramines d. Oxygen

d. Oxygen

Which metal, if in contact with cast iron, would become the most active (anode)? a. Aluminum b. Zinc c. Cadmium d. Mild steel

b. Zinc

Low alkalinity water becomes quite corrosive when it is heavily saturated with \_\_\_\_\_\_\_\_\_. a. lime. b. soda ash. c. oxygen. d. sodium bicarbonate.

c. oxygen.

Immediately before breakpoint chlorination occurs, which chemical species are destroyed? a. Aromatic hydrocarbons b. Aromatic hydrocarbons and aliphatic hydrocarbons c. Ammonia and chloroorganics d. Chloroorganics and chloramines

d. Chloroorganics and chloramines

Which is the most effective disinfectant for inactivating viruses? a. Hypochlorite ion b. Diatomic iodine c. Chloramines d. Chlorine dioxide

d. Chlorine dioxide

Which is the most effective disinfectant for inactivating protozoan cysts? a. chloramines b. Hypochlorous acid c. Ozone d. Bromine

c. Ozone

Which chemical oxidant would be most effective in removing color and for controlling tastes and odors? a. Ozone b. Potassium permanganate c. Chloramines d. Chlorine

a. Ozone

Which chemical oxidant is the weakest? a. Oxygen b. Ozone c. Potassium permanganate d. Chlorine dioxide

a. Oxygen

Why can hypochlorous acid (HOCl) penetrate bacterial surfaces better than hypochlorite ion (OCl^-)? ## Footnote a. Because it is a proton donor b. Because it is an acid c. Because it is a smaller molecule than OCl^- despite having a hydrogen atom; the hydrogen atom helps compact the molecule d. Because it is neutral

d. Because it is neutral

Which chlorine compound will produce the least detectable chloronous taste and odor? a. Hypochlorous acid b. Monochloramine c. Dichloramine d. Nitrogen trichloride

b. Monochloramine

Which type of pumps would be the most economical to use if large volumes of sodium hypochlorite were required? a. Chemical feed pumps using piston rods b. Chemical feed pumps using plunger drives c. Centrifugal pumps d. Solenoid-operated pumps

c. Centrifugal pumps

A disadvantage to using chloramines is \_\_\_\_\_\_\_\_\_. a. their vulnerability to nitrification. b. that they cannot penetrate biofilms in the distribution system. c. their propensity to form trihalomethanes. d. that their residual persistence in the distribution system is low.

a. their vulnerability to nitrification.

Where is the best place to add corrosive inhibitors such that disinfection can take place under more advantageous conditions at a conventional water treatment plant? ## Footnote a. Rapid mix basin b. Pre-filter c. Pre-clearwell d. Post clearwell

d. Post clearwell

Which method can be used to control scaling but is never used to control corrosion? a. Chelation b. Controlled CaCO₃ scaling c. Polyphosphate d. pH and alkalinity adjustment with lime

a. Chelation

How much more soluble is ozone in water than oxygen? a. 7.6 times b. About 10.0 times c. 12.0 times d. 20.0 times

d. 20.0 times

Which is the most effective ratio of hydrogen peroxide to ozone? a. 1:2 b. 2:5 c. 1:3 d. 1:4

a. 1:2

Which is the chlorine demand of nitrite? a. 2.0 parts chlorine to 1 part nitrite b. 2.5 parts chlorine to 1 part nitrite c. 4.0 parts chlorine to 1 part nitrite d. 5.0 parts chlorine to 1 part nitrite

d. 5.0 parts chlorine to 1 part nitrite

A sodium hypochlorite solution at room temperature will lose which percentage of its available chlorine content per month? a. 1 to 2% b. 2 to 4% c. 4 to 6% d. 6 to 8%

b. 2 to 4%

When supplied with air, ozone generators will produce about \_\_\_\_\_\_\_\_\_. a. 2% ozone. b. 5% ozone. c. 7% ozone. d. 12% ozone.

a. 2% ozone.

Which method for chlorine dioxide generation is most likely to have substantial amounts of chlorine in solution? ## Footnote a. Add chlorine to water, then this water to sodium citrate and sodium chlorate b. Add chlorine to water, then this water to hydrochloric acid and sodium chlorate c. Inject chlorine gas under vacuum into a stream of chlorite solution d. Add hydrochloric acid to a chlorite solution

b. Add chlorine to water, then this water to hydrochloric acid and sodium chlorate

Which chemical used for stabilization of potable water is a bacterial nutrient? a. Polyphosphate b. Lime c. Soda ash d. Sodium bicarbonate

a. Polyphosphate

Once formed, hypochlorous acid instantaneously establishes equilibrium as follows: HOCl ⇔ H+ + OCl- hypochlorous acid hypoclorite ion This equilibrium reaction at 200c has which characteristic? a. It contains 50% of HOCl and OCl- at a pH of 7.3 b. The reaction depends on concentration c. It responds slowly to pH changes d. It is completely reversible

d. It is completely reversible

Ultraviolet light used in disinfection is generated by mercury or \_\_\_\_\_\_\_\_\_\_. a. germanium. b. antimony. c. cesium. d. cadmium.

b. antimony.

The production of earthy-musty compounds, geosmin, and 2-methylisoborneol (MIB) by cyanobacteria are difficult to remove except when using \_\_\_\_\_\_\_\_\_\_\_. a. lime. b. ozone. c. aeration. d. filtration.

b. ozone.

Which chemical oxidant would be most effective for removing synthetic organics? a. Oxygen b. Chlorine c. Chloramines d. Chlorine dioxide

d. Chlorine dioxide

The advantage to using the oxidant oxygen is that it \_\_\_\_\_\_\_. a. is non-corrosive. b. has no by-products. c. causes small amount of scaling problems. d. is a strong oxidant.

b. has no by-products.

Which method for chlorine dioxide generation is best for large-scale application? ## Footnote a. Add chlorine to water, then this water to sodium citrate and sodium chlorate b. Add chlorine to water, then this water to hydrochloric acid and sodium chlorate c. Inject chlorine gas under vacuum into a stream of chlorite solution d. Add hydrochloric acid to a chlorite solution

c. Inject chlorine gas under vacuum into a stream of chlorite solution

Which is the commercial purity of fluorosilicic acid? a. 20 to 30% b. 20 to 40% c. 30 to 40% d. 35 to 48%

a. 20 to 30%

Which type of fluoride chemical should be used in down flow saturators? a. Tablets of sodium fluorosilicate b. Granular sodium silicofluoride c. Crystalline sodium fluoride d. Powdered sodium fluoride

c. Crystalline sodium fluoride

The decomposition products of sodium hypochlorite into chlorate and O₂ would be caused by which factor? a. Temperature b. Metallic impurities c. UV light d. pH

c. UV light

Which are the only two metals that can contact sodium hypochlorite; all other metals must be eliminated from storage vessels, piping, valves, and feed equipment? ## Footnote a. Titanium and tantalum b. Titanium and germanium c. Vanadium and germanium d. Vanadium and selenium

a. Titanium and tantalum

Sites that require chlorine vaporizers typically have feed rates that exceed \_\_\_\_\_\_\_\_\_. a. 450 lb/d. b. 800 lb/d. c. 1,000 lb/d. d. 2,000 lb/d.

d. 2,000 lb/d.

The deterioration of elastomeres by chloramines is enhanced by \_\_\_\_\_\_\_\_\_. a. higher pH. b. lower pH. c. higher temperatures. d. lower temperatures.

c. higher temperatures.

Most water treatment systems can limit nitrification by \_\_\_\_\_\_. a. maintaining a pH of 7.0 to 7.5. b. maintaining a chlorine to ammonia-nitrogen ratio between 4.5:1 and 5.0:1. c. limiting excess free ammonia to below 0.5 mg/L nitrogen. d. maintaining temperature between 18 and 28^oC.

b. maintaining a chlorine to ammonia-nitrogen ratio between 4.5:1 and 5.0:1.

If the percentage of chlorine delivered to a water treatment plant in liquid form is 12.5% chlorine, which chemical is it most likely to be? a. Calcium hypochlorite b. Sodium hypochlorite c. Chlorine d. Chlorine dioxide

b. Sodium hypochlorite

Chemical Additions Flashcards

(120 cards)