Wastewater Treatment Fundamentals, Exams of Nursing

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WASTEWATER CLASS 4 EXAM VIRGINIA

In an electrical circuit, the grounding wire is indicated by which color? - Answer ✔✔Green According to the Ohms Law, which electrical unit measures pressure? - Answer ✔✔Volts According to the Ohms Law, which electrical unit measures resistance? - Answer ✔✔Ohms According to the Ohms Law, which electrical unit measures current? - Answer ✔✔Amps How do you convert cubic feet to gallons? - Answer ✔✔Multiply by

How do you convert gallons to pounds? - Answer ✔✔Multiply by 8. 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. - Answer ✔✔ 90

Solution: 360 x 1, ------------- = 90 4, What is the most widely used dechlorination agent in a conventional chlorine gas plant? - Answer ✔✔Sulfur Dioxide What is the most prominent concern in failing to remove grit from the wastewater? - Answer ✔✔Excessive wear and damage on mechanical equipment What is the chemical formula for Sulfuric Acid? - Answer ✔✔H2SO What is the ideal velocity in a grit channel, in feet per second? - Answer ✔✔1 fps Conventional pump packing should be: - Answer ✔✔Tightened down to a drip In a primary clarifier, the expected performance for removing settleable solids is 90-95% removal. What about the removal of suspended solids?

• Answer ✔✔50%

When preparing a sample for laboratory analysis that involves acid and water, how should the sample be poured? - Answer ✔✔Always pour the acid into the water You are tasked with recording a manual flow sample in an open channel. Where will you position yourself, relative to the weir, to record the most accurate measure of flow? - Answer ✔✔Behind the weir, 4 times the maximum head of the weir Why must a positive displacement pump never be started against a closed discharge valve? - Answer ✔✔Excessive pressure may damage the line, the pump, and the motor A circular tank is 45 feet in diameter and has a depth of 10 feet. What is the detention time in hours when the flow is 1.42 MGD? - Answer ✔✔ 2 hours Solution: 0.785 x 45 x 45 x 10 x 7.48 x 24 ----------------------------------- = 2. 1,420, What is the most common device for measuring flow in an open channel? - Answer ✔✔V-notch weir, then ultrasonic flowmeter.

You need to make an adjustment to your aeration basin, and foam is the only characteristic you have data on. Over the last few days, the foam has become white, and billowy. What adjustment do you make? - Answer ✔✔Decrease WAS Over the last week, your mixed liquor color has changed from brown, to dark brown, to black. What adjustment should you make? - Answer ✔✔Increase WAS You receive a surge of high flow into your aeration basins, and as a result, you are developing an increasing, billowy sludge blanket in your secondary settling tanks. What adjustment should you make? - Answer ✔✔Increase RAS Your pond has turned a blue-green color and there are algae blooms on the surface. What corrective action do you take? - Answer ✔✔Add sodium Nitrate At what temperature does the BOD sample need to be preserved at? - Answer ✔✔At or below 6 degrees Celsius How do you detect a chlorine gas leak? - Answer ✔✔Using a rag soaked in ammonia to detect white fumes What is the surface loading rate of a circular tank with a diameter of 50 ft and a flow of 2.4 MGD? - Answer ✔✔1,223 gallons per feet squared

Solution: 0.785 x 50 x 50 = 1,962. 2,400, ----------- = 1, 1,962. When is the DO the highest in stabilization ponds? - Answer ✔✔Mid- afternoon How long are BOD tests incubated for? - Answer ✔✔5 days at 20 degrees celcius Corrosion in manholes is caused by? - Answer ✔✔hydrogen sulfide gas Which is heavier, chlorine or air? - Answer ✔✔Chlorine Total solids are made up of what? - Answer ✔✔Total Solids = Suspended Solids + Dissolved Solids In a stabilization pond, oxygen for aerobic bacteria comes from what form of plant life? - Answer ✔✔Algae

An imhoff cone is used to? - Answer ✔✔Determine the amount of settleable solids If discharge from a positive displacement pump is consistently changing between high and low volumes of discharge what is the most likely cause? - Answer ✔✔Shaft is out of alignment Organic nitrogen is determined using - Answer ✔✔The kjeldahl method You have just rewired a motor on a centrifugal pump. The pump is now running but generating little pressure and flow. What is the most likely cause? - Answer ✔✔Wrong direction of impeller rotation from improper rewiring The formation and collapse of gas pockets or bubbles on the blade of a centrifugal pump's impeller is known as what? - Answer ✔✔Cavitation Which of the following is the best description of Total Dynamic Head of a pump? - Answer ✔✔TDH = static height + static lift + friction loss Best type of flow measuring device in a closed channel to measure solids? - Answer ✔✔Magnetic flowmeter is best. Then venturi meter. Why is sodium hypochlorite sometimes added to the head of a plant? - Answer ✔✔To control odors.

What problems may arise from tightening the gland in a pump? - Answer ✔✔Excessive wear on shaft or shaft sleeve. A large number of amoebas would indicate what type of sludge? - Answer ✔✔Young sludge A large number of rotifers would indicate what type of sludge? - Answer ✔✔Old sludge Flagellates, Ciliates, and Rotifers are all part of what single-celled group? - Answer ✔✔Protozoa Which microorganism is responsible for converting ammonia nitrogen to nitrite? - Answer ✔✔Nitrosomonas Which microorganism is responsible for oxidizing nitrite into nitrate? - Answer ✔✔Nitrobacter Among all the organisms in activated sludge, what percentage is bacteria? - Answer ✔✔95% What does the Specific Oxygen Uptake Rate (SOUR) measure? - Answer ✔✔Amount of oxygen used by microorganisms to consume one gram of food

How many times greater is the reduction rate of aerobic bacteria versus anaerobic bacteria? - Answer ✔✔20 times - DOUBLE CHECK THIS ANSWER - NOT SURE OF THIS The casing surrounding the impeller on a pump is called the: - Answer ✔✔Volute Valves should be closed slowly to prevent: - Answer ✔✔Water hammer In an electrical circuit, a ___________ is used to reduce voltage where needed. - Answer ✔✔Transformer What is the problem with over-lubricating a pump bearing? - Answer ✔✔It may cause overheating. 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. - Answer ✔✔3,125 gallons per square feet Solution: 26 x 16 = 416 square feet 1,300, ---------- = 3, 416

What is the hydraulic detention time of a rectangular tank with a length of 26 ft, a width of 22 ft, and a height of 19 ft when the influent flow is 1.3 MGD? - Answer ✔✔1.5 hours Solution: 26 x 22 x 19 x 7.48 x 24 -------------------------- = 1. 1,300, How many minutes are in a day? - Answer ✔✔1, If a math formula answer is normally in hours, but the question is asking for minutes, multiply by 1440 instead of 24 Write out the entire Ohm's Law formula, including the units, and the properties they measure. - Answer ✔✔Amps (Current) = Volts (Pressure) / Ohm's (Resistance) 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? - Answer ✔✔502 lbs/day Solution:

Multiply flow in MGD x BOD concentration, then multiply it by 8.34 to convert gallons into pounds, since that is the unit they want. 1.28 x 47 x 8.34 = 501. Based upon the available data, what change should an operator make to achieve the optimum organic loading? Tanks available: 3 Tanks in service: 2 BOD concentration: 176 mg/L Flow: 6.5 MGD Tank diameter: 100 ft Tank depth: 6 ft The design organic loading rate is 200-300 lbs/1,000 cubic feet. - Answer ✔✔176 x 6.5 x 8.34 x 1000 / 0.785 x 100 x 100 x 6 x 2 tanks= 101 176 x 6.5 x 8.34 x 1000 / 0.785 x 100 x 100 x 6 x 1 tank= 203 Take a tank out of service so that there is only one tank in service. 203 is within design rate. Your aeration tank has the following protozoa populations by percent:

Stalked Ciliates 20% Nematodes: 20% Rotifers: 60% What action do you need to take? - Answer ✔✔Increase WAS 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, if any, has a higher pressure at the bottom? - Answer ✔✔They will both have THE SAME pressure at the bottom of the tank due to the hydrostatic paradox Which chemical will cause a decrease in pH? - Answer ✔✔Sulfuric acid Hydraulic Loading Rate Question - Answer ✔✔ Before repairing a pump's electrical circuit, what should you always make sure to do? - Answer ✔✔Disconnect the circuit breaker and Lock Out Tag Out Which of the following is a type of positive displacement pump: Axial Turbine

Educator Gear - Answer ✔✔Gear What do you call the total vertical distance that a pump pulls from, and discharges to? This can include both lowering and raising water. - Answer ✔✔Static head A positive displacement sludge pump should never be placed into operation with the _______________ closed. - Answer ✔✔Discharge valve If the bearing on a centrifugal pump is overheating, what should you check? - Answer ✔✔First, the lubrication. If lubrication is satisfactory, then inspect motor alignment If a centrifugal pump is losing its prime AFTER being started, what is the most likely cause? - Answer ✔✔Air is leaking into the pump through the stuffing box What separates the impeller from the volute and prevents backflow in a centrifugal pump? - Answer ✔✔The wear rings Why are check valves important? - Answer ✔✔They prevent backflow. Without them, water could freely travel from the discharge line back into the tank/wet well

What do you do if your stabilization pond is going "septic"? - Answer ✔✔Raise the level. The oxygen concentration will rise due to more water volume What is bulking? - Answer ✔✔Sludge blanket rises to the top of secondary clarifiers What causes bulking? - Answer ✔✔Mainly filamentous bacteria, then low pH. Sodium hypochlorite kills filamentous bacteria Describe the advantages of different pump seal technologies. - Answer ✔✔Pump packing - Lower up-front cost, easier installation and maintenance process Mechanical seal - Will save money in the long run, far more reliable option Which chemical serves as a coagulant, and will help settle sludge in a clarifier? Alum Lime Polymer Sodium Hypochlorite - Answer ✔✔Alum. Ferric Chloride is also an option. Both serve to remove phosphorus and encourage sludge settlement in clarifiers

Of the following, which is the most likely cause of electric motor failure: Dust New connection Moisture No friction - Answer ✔✔Moisture What is the slime on a trickling filter media called? - Answer ✔✔zoogleal film Shaft speed on a typical rbc should be between: - Answer ✔✔1-2 rpm Turbidity in wastewater is caused by: Color Dissolved Calcium Hardness Finely divided suspended material - Answer ✔✔Finely divided suspended material An active sludge in the aeration tank with an abundant available food supply will have a relatively:

High oxygen uptake and fast settling rate High oxygen uptake and slow settling rate Low oxygen uptake and fast settling rate Low oxygen uptake and slow settling rate - Answer ✔✔High oxygen uptake and slow settling rate What action can you take if your RBC is organically overloaded and the slough is turning pale white? - Answer ✔✔Place additional units in service 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 - Answer ✔✔F:M = 0. 176 x 0.85 x 8.34 / 2214 x 0.37 x 8.34 = 0. Your ideal F:M ratio is 0.25 - 0.35. What action do you take if your measured F:M ratio is too LOW? - Answer ✔✔Increase the Waste rate.

Your ideal F:M ratio is 0.25 - 0.35. What action do you take if your measured F:M ratio is too HIGH? - Answer ✔✔Decrease the Waste rate. What does white foam in your aeration tank indicate? - Answer ✔✔You are wasting more than required, and your SRT is low. What are the advantages of step-feed aeration tank? - Answer ✔✔when sludge bulking occurs in the aeration, addition of primary effluent in different steps in the aeration allows more even distribution of oxygenated environment. What is an advantage of low-rate or extended aeration tank? - Answer ✔✔In a small plant, low rate aeration tank combines the roles of primary clarifies and nitrogen removal into one. What are the effects of increasing WAS in the aeration tank for the following: SRT F/M MLSS MLVSS - Answer ✔✔SRT - decrease F/M - increase MLSS - decrease MLVSS (bugs) - decrease

Chlorine gas is classified as which of the following: High explosive liquid Non-toxic gas Powered compound Non-flammable compressed gas - Answer ✔✔Non-flammable compressed gas.

• Answer ✔✔