Wastewater Class 4 Exam Virginia-with 100% verified solutions-2024.docx, Exams of Advanced Education

Download Wastewater Class 4 Exam Virginia-with 100% verified solutions-2024.docx and more Exams Advanced Education in PDF only on Docsity! Wastewater Class 4 Exam Virginia-with 100% verified solutions-2024 In an electrical circuit, the grounding wire is indicated by which color? Green According to the Ohms Law, which electrical unit measures pressure? Volts According to the Ohms Law, which electrical unit measures resistance? Ohms According to the Ohms Law, which electrical unit measures current? Amps How do you convert cubic feet to gallons? Multiply by 7.48 How do you convert gallons to pounds? Multiply by 8.34 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 Solution: 360 x 1,000 = 90 4,000 What is the most widely used dechlorination agent in a conventional chlorine gas plant? Sulfur Dioxide What is the most prominent concern in failing to remove grit from the wastewater? Excessive wear and damage on mechanical equipment What is the chemical formula for Sulfuric Acid? H2SO4 What is the ideal velocity in a grit channel, in feet per second? 1 fps Conventional pump packing should be: 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? 50% 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 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 Solution: 0.785 x 50 x 50 = 1,962.5 2,400,000 = 1,223 1,962.5 When is the DO the highest in stabilization ponds? Mid-afternoon How long are BOD tests incubated for? 5 days at 20 degrees celcius Corrosion in manholes is caused by? hydrogen sulfide gas Which is heavier, chlorine or air? Chlorine Total solids are made up of what? Total Solids = Suspended Solids + Dissolved Solids In a stabilization pond, oxygen for aerobic bacteria comes from what form of plant life? Algae An imhoff cone is used to? 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? Shaft is out of alignment Organic nitrogen is determined using 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? 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? Cavitation Which of the following is the best description of Total Dynamic Head of a pump? TDH = static height + static lift + friction loss Best type of flow measuring device in a closed channel to measure solids? Magnetic flowmeter is best. Then venturi meter. Why is sodium hypochlorite sometimes added to the head of a plant? To control odors. In an electrical circuit, a is used to reduce voltage where needed. Transformer What is the problem with over-lubricating a pump bearing? 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. 3,125 gallons per square feet Solution: 26 x 16 = 416 square feet 1,300,000 ---------- = 3,125 416 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? 1.5 hours Solution: 26 x 22 x 19 x 7.48 x 24 = 1.50 1,300,000 How many minutes are in a day? 1,440 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. 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? 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 = 501.73 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. 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: 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 What separates the impeller from the volute and prevents backflow in a centrifugal pump? The wear rings Why are check valves important? 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"? Raise the level. The oxygen concentration will rise due to more water volume What is bulking? Sludge blanket rises to the top of secondary clarifiers What causes bulking? Mainly filamentous bacteria, then low pH. Sodium hypochlorite kills filamentous bacteria 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 Which chemical serves as a coagulant, and will help settle sludge in a clarifier? Alum Lime Polymer Sodium Hypochlorite 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 Moisture What is the slime on a trickling filter media called? zoogleal film Shaft speed on a typical rbc should be between: 1-2 rpm Turbidity in wastewater is caused by: Color Dissolved Calcium Hardness Finely divided suspended material Finely divided suspended material An active sludge in the aeration tank with an abundant available food supply will have a relatively: