Wastewater Operator D Exam Prep

An industry discharges wastewater into the collection system of a city. If a discharge permit is required of the industry to discharge wastewater, who issues the permit?

The city.

Why should oils and greases be removed from wastewaters?

They cause flow obstructions in pipes.

Corrosion problems can be attributed to...

low pH

An equalization tank which handles a waste with a high grit content has been experiencing a reduction in volume capacity. What could be the cause of this?

Improperly located mixer

DAF (Dissolved Air Flotation) is one method used for...

oil removal

Given the following data, find the detention time in hours for a flotation unit.

TSS = 98 mg/L

Tank size = 60 ft long, 30 ft wide, 8 ft deep

Water depth = 7 ft

Q = 470,000 GPD

4.8 hrs

The green wire in a four-wire cable which feeds an electric motor indicates...

ground

Friction loss in a discharge pipe will tend to...

increase TDH (Total Dynamic Head)

What maintenance would be performed on a pH probe?

Check electrolyte

What can increase the pH of water?

NaOH (sodium hydroxide) caustic

What is the most reliable of backflow preventers?

A reduce pressure (RP) device

What industry produces a low chemical oxygen demand (COD) waste?

Metal finishing

What is a good response to a fuse that repeatedly blows in a control panel?

Determine the cause

Which type of flow measurement device might require purge water?

A venturi meter

A solute that exists almost completely as ions is a/an

Strong electrolyte

How many pounds of lime must be added to a volume of 34,000 gallons in order to give it a concentration of 50 ppm?

14.2 lbs

When lubricating electric motors, extra grease increases…

Temperature

One concern when handling infectious materials in the laboratory is…

Personal hygiene

What is the primary concern in effluent disposal?

Public health

Flow velocity is commonly measure in units of what?

ft/sec

Convert -38 °F to °C

-38.9 °C

The oil and grease concentration entering a plant is 387 mg/L and the concentration leaving the plant is 56 mg/L. What is the removal efficiency?

86%

0.001 mg/L is the same as…

1 part per billion

The ability of water to neutralize acids is called what?

Alkalinity

What is 1 ft³ in in³?

1728 in³

Which treatment process would broken flight boards be associated with?

Clarification

What would prevent land application of sludge?

High metals concentration

What is the first thing an operator should do if he/she notices excessive vibration at a chemical feeder?

Turn it off

Total solids actually refers only to what?

Suspended, settleable, and dissolved solids

Probes, floats, and bubbler tubes are commonly used for what?

Level indication

Wastewater treatment plant operators in South Carolina are certified by what?

Environmental Certification Board

In flow equalization, contaminant consistency is best maintained by what?

Mixers

Short-circuiting in a settling basin is prevented by what?

Baffles

A pump delivers 380 GPM at 50 ft of head. What is the pressure equivalent of the discharge head?

21.6 psi

Which of the following represents the greatest threat to receiving waters when meat-packing waters are discharged?

Oxygen demand

When the concentration of acid is greater than that of the caustic, the sample is what?

Acidic

Which valve allows flow in one direction only?

Check valve

The part of a pump which keeps water in the volute and keeps air out is called the what?

Packing

Which part usually wears out first on a reciprocating pump?

The packing

What is a doctor blade used for?

To remove oil from a rotating bearing

What pumps should never be started with the discharge valve closed?

Piston pumps

Dye is put in the wastestream and travels a distance of 20 feet in 9 seconds. What is the flow velocity?

2.2 ft/sec

Identify the following symbols:

O
N
Cu
Al
H
Fe

Oxygen
Nitrogen
Copper
Aluminum
Hydrogen
Iron

Identify the following symbols:

K
Na
Cl
CN
Cr
H₂SO₄

Potassium
Sodium
Chlorine
Cyanide
Hexavalent cromium
Sulfuric acid

Identify the following symbols:

NaOH
HCl
Zn
Hg
Ag
Pb

Sodium hydroxide
Hydrochloric acid
Zinc
Mercury
Silver
Lead

Three phase current is…

Alternating current

Electrical current flow is measured in units of…

Amperes

What piece of labware is commonly used to measure suspended solids?

Imhoff cone

The effects of most pollution are enhanced by…

Heat

A plant discharges a suspended solids concentration of 12 ppm with a flow of 2.34 MGD. How many pounds of suspended solids are entering the receiving waters?

234 lbs

A tank is 15 feet high by 8 feet in diameter. If filled, how many liters will it hold?

21,339.6 L

What textile product produces the greatest waste load in terms of biochemical oxygen demand (BOD)?

Wool

What is commonly used to remove calcium precipitates from a pH probe?

HCl (hydrochloric acid)

What would be the accepted first aid for first degree burns?

Immerse in cold water

What flow measurement device is best suited for measuring sludge flow?

A magnetic flow meter

In flow measurement, pressure differential is most commonly associated with?

Venturi meters

What is applied to the insides of tanks in order to prevent corrosion?

Rubber

In what industry is heavy metals a common contaminant?

Wool

What waste requires CN (cyanide) destruction?

Metal finishing

Which waste characteristic would contribute to scaling in pumps and pipes?

Alkalinity

What industry generally produces a wastewater with a low TSS level?

Metal finishing

What mill most likely contributes the most wastewater to a collection system?

A paper mill

Pump cavitation can be caused by what?

Low suction head and suction valve partially closed

Pertinent information concerning a particular hazardous substance of mixture can be found in a/an…

MSDS

What pH value and below is considered the most corrosive substance?

3.0

A very toxic chemical used to perform the COD test is what?

Mercuric sulfate

You could standardize the pH meter with pH buffers 7 and 10 if the expected pH was what?

9

What is used to measure settleable solids?

Imhoff cone

What is the purpose of a backflow preventer?

To prevent contamination

How many contact-hours of relevant training must an operator receive in a three-year period in order to maintain a wastewater certification in SC?

18

When organic wastes are discharged to receiving waters, oxygen is depleted by what?

Bacteria

Hydrogen sulfide gas gives off odors similar to what?

Rotten eggs

What would be effective in cleaning up a liquid polymer spill in the chemical storage area?

Salt

What is commonly used to adjust pH?

Ca(OH)₂

One milliliter is what fraction of a liter?

1/1000

What device removes oil with the lowest water content?

A rotating drum

The specific gravity of oil causes it to what?

Float in water

The normal cause of electric motor failure is what?

Dirt, moisture, and friction

What is an example of a Class C fire?

An electrical fire

A chain-of-custody record kept in a laboratory is used for what?

Sample tracking

According to OSHA, what is the minimum oxygen content for safe entry in a confined space?

19.5%

Studies of confined space fatalities have shown that ____ percent of these fatalities are workers attempting to rescue other workers.

50

A water seal on a pump serves a dual purpose. It acts as a lubricant and it also does what?

Keeps gritty material from entering the packing box

The elevation of any pump above the source of supply should not exceed _____ feet.

22, between 15 to 25 feet

The three common types of plastic pipe are listed as PVC, PE, and ABS. These names refer to what?

The composition of the pipe

Prior to repairing a pump’s electrical circuit, which actions should you take?

Disconnect the circuit breaker, place a red tag stating “Do No Activate”, and lock it out

Parameters tested from a composite sample for influent would included what?

COD (composite sample)

What effluent parameter would be measured on a continuous basis?

Flow

Keeping a sample at 4 °C will what?

Reduce biological action

The use of a holding tank to “average out” the flow and/or concentration of contaminants is called what?

Equalization

When should the temperature of an effluent grab sample be measured?

Immediately

What test determines the efficiency of a primary clarifier?

Settleable solids

Disaster preparedness plans should what?

Reduce confusion

What does the segregation of process wastes and cooling water accomplish?

Saves money

Who issues NPDES permits?

SCDES

What would enhance oil flotation?

Heat

What hazard is associated with a polymer spill?

Slipping

How does one read a meniscus when measuring water in a graduated cylinder?

Align the bottom of the curve with the graduation

How much is 74% of 670?

496

Find the average of the following flow readings:

223, 211, 109, 300, 346, 295, 276

251