Water Treatment Exam Study Questions

What is a typical filter run time for a high-rate filter system?

24 hours

A water system is considered public if it has at least 15 service connections or serves ________ or more person __________ or more days each year.

25,60

Convert 85 degrees Fahrenheit to Celsium

29 degrees Celsius

What is the velocity of flow in feet per second for a 6 inch diameter pipe delivering water at 295 gpm?

3.35 fps

How many zones are there in a conventional sedimentation basin?

4 zones

Water systems must provide at least _________ removal or inactivation of viruses between a point where the raw water is not subject to recontamination by surface water runoff and a point downstream before or at the first customer.

4-log

What is the normal strength of sodium hypochlorite as percent available chlorine?

5-15%

Calcium hypochlorite is usually available in what strength? (% available chlorine)

65-70%

According to the surface water treatment rule, how often must a system serving more than 500 people sample their filtered water for turbidity?

Every 4 hours

Which chemical is often used with lime softening?

Ferric sulfate

The "Rule of reasonable sharing" is called the: ________.

Riparian doctrine

From the list below, which chemical will raise pH? -Ferric chloride -alum -soda ash -sulfuric acid

Soda ash

Water that runs into streams, rivers and lakes after rainfall is called

Surface runoff

The turbidity leaving a slow sand filter must be

less than or equal to 1.0 ntu in 95% of the measurements collected each month.

The most common solution feeder used for liquid coagulants and coagulant aids is the ___________.

metering pump

_________ is commonly called swamp gas

methane

Why is air added during the reverse flow process of a microfiltration plant?

To improve the removal of fouling material

What is it called when water moves from leaves, grasses, and other plants to the atmosphere?

Transpiration

What test is used to indicate the clarity of water?

Turbidity

What agency is responsible for establishing drinking water standards?

USEPA

Which is the maximum residual disinfection level goal for chlorine?

4 mg/L

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

500 psi

If the desired dose of chlorine is 2 mg/L, how many pounds per day of chlorine will be required to treat an average flow of 3.1 MGD?

52 lb/day

If a pump discharges 10,350 gallons during a 3 hour and 15 minute period, how many gallons per minute is the pump discharging?

53 gpm

What is a normal groundwater pH level?

6.0-8.5 pH

Why do algae cause pH to go down during the day.

During the day, algae undergoes photosynthesis which removes carbon dioxide from the water causing pH to increase.

Which membrane process has been used for water softening and DBP precursor removal?

Nanofiltration

Carbon dioxide is removed from water by the aeration process due to _______.

Stripping

Who certifies water treatment plant laboratories for the measurement of total coliforms, fecal coliforms, and heterotrophic plate counts?

USEPA or the state

Which of the following material groups are commonly used to make GAC used in municipal water treatment application? -lignite coal, kingsford coal -anthracite, garnet -bituminous coal, anthracite coal -coconut shell, bituminous coal

coconut shell, bituminous coal

Of the following, which filter uses pressure for filtration? -Sand filter -Monomedium filter -rapid filter -diatomaceous earth filter

diatomaceous earth filter

The material that accumulates on the surface of a dissovled-air flotation unit is called

float

The ________ creates the vacuum that is required to operate the chlorinator.

injector

Acids, bases, and salts lacking the element carbon are ________ compounds.

inorganic

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

potassium permanganate

Determine the drawdown of a well (in feet) if the well yields 200 gpm and the specific yield is 15.5 gpm/ft.

13 ft.

A chemical feed pump has caused the tank level to drop 18 inches during an 8 hour shift. The tank is 10 feet in diameter. What is the feed rate in gallons per day?

2,642 gpd

Determine the detention time in hours for a sedimentation basin that measures 35 ft wide by 15 ft. deep by 130 ft. long. Plant flow is 5.8 MGD.

2.1 hours

Which would be considered very hard water measured in mg/L as CaCO3? -80 mg/L -200 mg/L -75 mg/L -150 mg/L

200 mg/L

If a storage tank has a diameter of 20 ft, and is 12 ft tall, how many gallons of water can it hold if it is completely filled?

28,185 gallon

What is the feet of head at the discharge side of a pump that is pumping against a pressure of 125 psi?

289 ft.

For water system using conventional treatment or direct filtration, the turbidity level of representative samples of a system's filtered water must be less than or equal to ______ NTU in at least 95% of the samples collected each month.

0.3

How many samples can be coliform positive if a water system collects less than 40 samples per and the system still remain in compliance with the maximum contaminant level for total coliforms?

1

Systems that collect fewer than 40 total coliform samples each month are allowed ____ positive samples without violating the total coliform rule

1

Below what level should the turbidity of settled water before it is applied to the filters (post sedimentation process) be kept?

1 to 2 ntu

To calculate free chlorine residual, the contact time must be at least

10 minutes

At what temperature will chlorine cylinder fusible plug melt?

158-165 degrees fahrenheit

Samples to be analyzed for total coliform by the total coliform fermentation technique, must be kept below ______ degrees Celsius during transit.

10

How long does ozone generally last when it is dissolved in water for disinfection purposes?

A few seconds to a few minutes

Auxiliary equipment used for the fluoridation process includes:

A flow meter used for flow pacing (automatic chemical feed adjustment)

Following the lime softening process, how is the water stabilized?

Addition of carbon dioxide

Where should a GAC process be installed at a surface water treatment plant to be most cost effective when used to remove natural organic material?

After filtration

Addition of lime, caustic soda, or sodium bicarbonate may be required to aid the coagulation and flocculation of waters low in _______.

Alkalinity

What term describes the capacity of water to neutralize a strong acid?

Alkalinity

What is the purpose of a check valve?

Allow flow in only one direction

One turn open on a chlorine cylinder will _________.

Allow maximum flow

Self-contained breathing apparatus (SCBA) units: -Should have all straps removed so they fit in their cases -should not be stored far away from the chlorine location -are fitted with a low-air-pressure alarm that alerts the wearer to leave the contaminated site -are different from the equipment used by SCUBA divers

Are fitted with a low-air-pressure alarm that alerts the wearer to leave the contaminated site

Under no circumstances should a composite sample be collected for _________ analysis.

Bacteriological

Which are the two main elements that cause water hardness?

Calcium and magnesium

Hard water scale is usually caused by

Calcium carbonate

Which commonly used base material produces an activated carbon with the smallest pore size?

Coconut shell

What is used as an indicator of pathogens in a water supply?

Coliform group bacteria

What are the three routine control tests performed on an aeration system?

DO, pH, Temperature

The residual chlorine test requires the use of what chemical?

DPD (N,N-diethyl-p;phenylenediamine)

Killing or inactivation of pathogenic organisms in drinking water is called _______.

Disinfection

What does color in surface water indicate?

Dissolved organics may be present

What type of PAC feed system should a plant that plans to only feed powdered activated carbon periodically install?

Dry feed system

What device collects the settled water as it leaves the sedimentation basin?

Effluent launder

Currently, which is the most frequently diagnosed waterborne disease in the United States?

Giardiasis

Sodium fluoride: -Has no odor -is delivered as a liquid -is a straw yellow color -has a solution pH of about 2.0 pH units

Has no odor

From the following list, which will contribute to the creation of an algal bloom? -High winds -High turbidity -High nutrient loading -High ambient temperature

High nutrient loading

pH measurements indicates ______.

Hydrogen ion concentration

During the day, algae will cause the pH in a reservoir to _______?

Increase

Which groundwater contaminant forms a precipitate when oxidized?

Iron

How should valve stem packing be staggered if only two rings are used in a valve's stuffing box?

Joints staggered 90-180 degrees

Bar screens are used to remove _________.

Large debris

Which of the following metals may enter a consumer's drinking water as a result of corrosive water? -gold -Silver -Tungsten -Lead

Lead

What are the turbidity requirements for diatomaceous earth filtration?

Less than or equal to 1.0 ntu in 95% of the measurements collected each month.

Which part listed below is a major component of a turbidimeter?

Light source

What is the best available technology (BAT) for removing radium-226 and radium-228 from source water?

Lime softening

For public surface water system operating without filtration, the surface water treatment rule requires them to __________.

Maintain a CxT value above the minimum required

To permit maximum withdrawal rate when opening a chlorine cylinder valve __________.

Open only one turn

A stream that flows all year long is called a __________.

Perennial stream

Which radioactive nuclide is a gas? -Artificial Radionuclides -Radium -Radon -Uranium

Radon

What water quality problem does a carbon dioxide level of 50 mg/L create in a water supply?

Reduces pH which makes the water corrosive

What is the function of sodium thiosulfate in the coliform sample bottle?

Remove chlorine residual prior to analysis

How does water temperature impact the solubility of gases in water?

Water temperature and solubility are inversely related

manganese can cause a __________ stain on clothing and plumbing fixtures

black

If ammonia vapor combines with chlorine gas leaking from a cylinder, what will appear?

white cloud

What is the term "C value" a description of?

A number that describes the smoothness of a pipe's interior surface.

When/where is powdered activated carbon (PAC) usually added to the treatment process?

Before the coagulation-flocculation process

How often should greased bearings be lubricates when in full service?

Every 3 to 6 months

What is the health affect associated with nitrates?

Methemoglobinemia (blue baby syndrome)

Which membrane process is most comparable to a conventional gravity sand filter?

Microfiltration

From the list, which is an indication of bearing failure: -Excessive packing leakage -Noise coming from the pump -Increase in pump discharge pressure -Foul odor in discharge water

Noise coming from the pump

Ion exchange softening processes can be used for direct groundwater treatment as long as turbidity and ________ levels are not too high.

iron

What is the most common water complaint?

poor taste and odor

_______ could cause pink water problems.

potassium permanganate

The buildup of corrosion products on the inside of iron pipes is known as

tuberculation

Which of the following diseases is transmitted by drinking water? -Tuberculosis -measles -mumps -typhoid

typhoid