Wastewater Class 4 Exam Virginia

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Questions and Answers

In an electrical circuit, the grounding wire is indicated by which color?

Red

Black

Blue

Green (correct)

According to Ohm's Law, which electrical unit measures pressure?

Volts

According to Ohm's Law, which electrical unit measures resistance?

Ohms

According to Ohm's Law, which electrical unit measures current?

Amps Signup and view all the answers

How do you convert cubic feet to gallons?

Multiply by 7.48 Signup and view all the answers

How do you convert gallons to pounds?

Multiply by 8.34 Signup and view all the answers

Calculate the SVI of your aeration basin when your 30-minute settleable sample is 360 mL/L and your average mixed liquor suspended solids concentration is 4000 mg/L.

90 Signup and view all the answers

What is the most widely used dechlorination agent in a conventional chlorine gas plant?

Sulfur Dioxide Signup and view all the answers

What is the most prominent concern in failing to remove grit from the wastewater?

Excessive wear and damage on mechanical equipment Signup and view all the answers

What is the chemical formula for Sulfuric Acid?

H2SO4 Signup and view all the answers

What is the ideal velocity in a grit channel, in feet per second?

1 fps Signup and view all the answers

Conventional pump packing should be:

Tightened down to a drip Signup and view all the answers

In a primary clarifier, the expected performance for removing settleable solids is 90-95%. What about the removal of suspended solids?

50% Signup and view all the answers

When preparing a sample for laboratory analysis that involves acid and water, how should the sample be poured?

Always pour the acid into the water Signup and view all the answers

Where should you position yourself, relative to the weir, to record the most accurate measure of flow?

Behind the weir, 4 times the maximum head of the weir Signup and view all the answers

Why must a positive displacement pump never be started against a closed discharge valve?

Excessive pressure may damage the line, the pump, and the motor Signup and view all the answers

What is the detention time in hours when a circular tank is 45 feet in diameter and has a depth of 10 feet with a flow of 1.42 MGD?

2 hours Signup and view all the answers

What is the most common device for measuring flow in an open channel?

V-notch weir, then ultrasonic flowmeter Signup and view all the answers

What adjustment do you make if your aeration basin foam is white and billowy?

Decrease WAS Signup and view all the answers

What adjustment do you make if your mixed liquor color has changed from brown, to dark brown, to black?

Increase WAS Signup and view all the answers

What adjustment should you make if you receive a surge of high flow into your aeration basins, resulting in an increasing sludge blanket?

Increase RAS Signup and view all the answers

What corrective action do you take if your pond has turned a blue-green color and there are algae blooms?

Add sodium Nitrate Signup and view all the answers

At what temperature does the BOD sample need to be preserved?

At or below 6 degrees Celsius Signup and view all the answers

How do you detect a chlorine gas leak?

Using a rag soaked in ammonia to detect white fumes Signup and view all the answers

What is the surface loading rate of a circular tank with a diameter of 50 ft and a flow of 2.4 MGD?

1,223 gallons per feet squared Signup and view all the answers

When is the DO the highest in stabilization ponds?

Mid-afternoon Signup and view all the answers

How long are BOD tests incubated for?

5 days at 20 degrees Celsius Signup and view all the answers

Corrosion in manholes is caused by?

Hydrogen sulfide gas Signup and view all the answers

Which is heavier, chlorine or air?

Chlorine Signup and view all the answers

Total solids are made up of what?

Total Solids = Suspended Solids + Dissolved Solids Signup and view all the answers

In a stabilization pond, oxygen for aerobic bacteria comes from what form of plant life?

Algae Signup and view all the answers

An Imhoff cone is used to?

Determine the amount of settleable solids Signup and view all the answers

If discharge from a positive displacement pump is inconsistently changing, what is the most likely cause?

Shaft is out of alignment Signup and view all the answers

Organic nitrogen is determined using?

The Kjeldahl method Signup and view all the answers

What is the most likely cause if a motor on a centrifugal pump generates little pressure and flow?

Wrong direction of impeller rotation from improper rewiring Signup and view all the answers

The formation and collapse of gas pockets on the blade of a centrifugal pump's impeller is known as what?

Cavitation Signup and view all the answers

Which of the following is the best description of Total Dynamic Head of a pump?

TDH = static height + static lift + friction loss Signup and view all the answers

Best type of flow measuring device in a closed channel to measure solids?

Magnetic flowmeter is best. Then venturi meter. Signup and view all the answers

Why is sodium hypochlorite sometimes added to the head of a plant?

To control odors Signup and view all the answers

What problems may arise from tightening the gland in a pump?

Excessive wear on shaft or shaft sleeve Signup and view all the answers

A large number of amoebas would indicate what type of sludge?

Young sludge Signup and view all the answers

A large number of rotifers would indicate what type of sludge?

Old sludge Signup and view all the answers

Flagellates, Ciliates, and Rotifers are all part of what single-celled group?

Protozoa Signup and view all the answers

Which microorganism is responsible for converting ammonia nitrogen to nitrite?

Nitrosomonas Signup and view all the answers

Which microorganism is responsible for oxidizing nitrite into nitrate?

Nitrobacter Signup and view all the answers

Among all the organisms in activated sludge, what percentage is bacteria?

95% Signup and view all the answers

What does the Specific Oxygen Uptake Rate (SOUR) measure?

Amount of oxygen used by microorganisms to consume one gram of food Signup and view all the answers

How many times greater is the reduction rate of aerobic bacteria versus anaerobic bacteria?

The casing surrounding the impeller on a pump is called the:

Volute Signup and view all the answers

Valves should be closed slowly to prevent:

Water hammer Signup and view all the answers

In an electrical circuit, a ___________ is used to reduce voltage where needed.

Transformer Signup and view all the answers

What is the problem with over-lubricating a pump bearing?

It may cause overheating. Signup and view all the answers

What is the surface loading rate of a rectangular tank with a length of 26 ft and a width of 16 ft? The flow coming in is 1.3 MGD.

3,125 gallons per square foot Signup and view all the answers

What is the hydraulic detention time of a rectangular tank with dimensions 26 ft by 22 ft by 19 ft when the influent flow is 1.3 MGD?

1.5 hours Signup and view all the answers

How many minutes are in a day?

1,440 Signup and view all the answers

Write out the entire Ohm's Law formula, including the units, and the properties they measure.

Amps (Current) = Volts (Pressure) / Ohms (Resistance) Signup and view all the answers

Your plant is discharging 1.28 MGD at the outfall. The BOD concentration in your discharge is 47 mg/L. What is the quantity of BOD discharged in pounds per day?

502 lbs/day Signup and view all the answers

What change should an operator make to achieve the optimum organic loading when given certain data?

Take a tank out of service so that there is only one tank in service. Signup and view all the answers

Your aeration tank has the following protozoa populations by percent. What action do you need to take if stalked ciliates are 20%, nematodes 20%, and rotifers 60%?

Increase WAS Signup and view all the answers

You have two tanks that are different shapes but have the same surface area at the bottom. Both tanks contain the same volume of water. Which tank has a higher pressure at the bottom?

They will both have the same pressure at the bottom of the tank due to the hydrostatic paradox Signup and view all the answers

Which chemical will cause a decrease in pH?

Sulfuric acid Signup and view all the answers

Before repairing a pump's electrical circuit, what should you always make sure to do?

Disconnect the circuit breaker and Lock Out Tag Out Signup and view all the answers

Which of the following is a type of positive displacement pump?

Gear Signup and view all the answers

What do you call the total vertical distance that a pump pulls from, and discharges to?

Static head Signup and view all the answers

A positive displacement sludge pump should never be placed into operation with the _______________ closed.

Discharge valve Signup and view all the answers

If the bearing on a centrifugal pump is overheating, what should you check?

First, the lubrication. If lubrication is satisfactory, then inspect motor alignment Signup and view all the answers

If a centrifugal pump is losing its prime after being started, what is the most likely cause?

Air is leaking into the pump through the stuffing box Signup and view all the answers

What separates the impeller from the volute and prevents backflow in a centrifugal pump?

The wear rings Signup and view all the answers

Why are check valves important?

They prevent backflow. Without them, water could freely travel from the discharge line back into the tank/wet well Signup and view all the answers

What do you do if your stabilization pond is going 'septic'?

Raise the level. The oxygen concentration will rise due to more water volume Signup and view all the answers

What is bulking?

Sludge blanket rises to the top of secondary clarifiers Signup and view all the answers

What causes bulking?

Mainly filamentous bacteria, then low pH. Sodium hypochlorite kills filamentous bacteria Signup and view all the answers

Describe the advantages of different pump seal technologies.

Pump packing - Lower up-front cost, easier installation and maintenance process. Mechanical seal - Will save money in the long run, far more reliable option Signup and view all the answers

Which chemical serves as a coagulant and will help settle sludge in a clarifier?

Alum Signup and view all the answers

Of the following, which is the most likely cause of electric motor failure?

Moisture Signup and view all the answers

What is the slime on a trickling filter media called?

Zoogleal film Signup and view all the answers

Shaft speed on a typical RBC should be between:

1-2 rpm Signup and view all the answers

Turbidity in wastewater is caused by:

Finely divided suspended material Signup and view all the answers

An active sludge in the aeration tank with an abundant available food supply will have a relatively:

High oxygen uptake and slow settling rate Signup and view all the answers

What action can you take if your RBC is organically overloaded and the slough is turning pale white?

Place additional units in service Signup and view all the answers

What is the Food to Microorganism ratio for the following aeration tank: Aeration tank volume: 0.37 MGD, MLVSS: 2214 mg/L, Aeration tank influent flow: 0.85 MGD, Aeration tank BOD: 176 mg/L?

F:M = 0.18 Signup and view all the answers

Your ideal F:M ratio is 0.25 - 0.35. What action do you take if your measured F:M ratio is too LOW?

Increase the Waste rate Signup and view all the answers

Your ideal F:M ratio is 0.25 - 0.35. What action do you take if your measured F:M ratio is too HIGH?

Decrease the Waste rate Signup and view all the answers

What does white foam in your aeration tank indicate?

You are wasting more than required, and your SRT is low Signup and view all the answers

What are the advantages of step-feed aeration tank?

When sludge bulking occurs in the aeration, addition of primary effluent in different steps in the aeration allows more even distribution of oxygenated environment Signup and view all the answers

What is an advantage of a low-rate or extended aeration tank?

In a small plant, low rate aeration tank combines the roles of primary clarifies and nitrogen removal into one Signup and view all the answers

What are the effects of increasing WAS in the aeration tank for the following: SRT, F/M, MLSS, MLVSS?

SRT - decrease; F/M - increase; MLSS - decrease; MLVSS (bugs) - decrease Signup and view all the answers

Chlorine gas is classified as which of the following?

Non-flammable compressed gas Signup and view all the answers

Study Notes

Electrical Circuit Basics

Grounding wire in an electrical circuit is green.
According to Ohm's Law, voltage is measured in volts (pressure), resistance in ohms, and current in amps.

Units and Measurements

Convert cubic feet to gallons by multiplying by 7.48.
Convert gallons to pounds by multiplying by 8.34.
Surface loading rate = flow (gallons) / tank surface area (square feet).

Wastewater Treatment Processes

The ideal velocity in a grit channel is 1 ft/s.
A primary clarifier typically removes 90-95% of settleable solids and around 50% of suspended solids.
Use sulfur dioxide as the main dechlorination agent in chlorine gas plants.

Equipment and Operations

Positive displacement pumps should not operate against a closed discharge valve due to potential damage.
Maintain DO levels highest in stabilization ponds typically in mid-afternoon.
Monitor BOD tests by incubating at 20°C for 5 days.

Sludge and Microbiology

Excessive mechanical wear in wastewater systems can occur without grit removal.
Young sludge is indicated by a high number of amoebas; old sludge by a prevalence of rotifers.
Specific bacteria like Nitrosomonas convert ammonia to nitrite, while Nitrobacter oxidizes nitrite to nitrate.

Sampling and Analysis

Always pour acid into water for safe sample preparation.
Detect chlorine gas leaks using ammonia-soaked rags to identify white fumes.

Troubleshooting and Maintenance

Over-tightening pump packing can cause excessive wear; lubricate bearings to prevent overheating.
If a centrifugal pump loses prime, check for air leaks at the stuffing box.

Adjustments in Aeration Tanks

Increase Waste Activated Sludge (WAS) if mixed liquor color changes to black or if there’s a high number of rotifers.
Decrease WAS if foam in the aeration basin turns white and billowy.
For high flow surges causing sludge blanket growth in secondary settling tanks, increase Return Activated Sludge (RAS).

Chemical Management

Sulfuric acid is used to decrease pH.
Alum is effective as a coagulant in clarifiers, aiding in sludge settlement.

Operational Optimization

Achieve optimum organic loading by adjusting tank usage; data indicates lower loading rates lead to better performance.
Maintain optimal Food to Microorganism (F:M) ratios by adjusting WAS according to measured values.

Miscellaneous

Hydrostatic principles dictate that pressure at the bottom of tanks remains constant regardless of shape, given the same area and volume.
Operators should Lock Out Tag Out (LOTO) before servicing electrical circuits.
Chlorine gas is categorized as a non-flammable compressed gas.

Studying That Suits You

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Description

Test your knowledge on electrical terminology related to wastewater management in Virginia. This flashcard set focuses on Ohm's Law and electrical circuit components, including the grounding wire, pressure, resistance, and current measurements. Perfect for students preparing for the Wastewater Class 4 exam.