Wastewater Treatment Class III Exam Prep FREE Sample Exam

During storm peaks the primary clarifiers lose capture badly for about two hours, forwarding a solids surge that upsets the aeration basins for the rest of the day. Equalization volume is available upstream. What is the best wet-weather strategy?

Push the full peak through the primaries as fast as possible so the basins empty sooner, and accept the capture loss as the unavoidable price of wet weather

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Raise primary sludge withdrawal to its maximum for the whole storm so the blankets stay thin, even though the withdrawn sludge runs dilute for many hours

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Shave the hydrograph peak into equalization so the primaries see a capped, steadier flow

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Take one primary clarifier out of service during the peak so the remaining units run deeper and settle the storm solids by gravity over a longer path

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A plant flowing 3.12 MGD sets a ferric dose of 14 mg/L from its effluent phosphorus trend. How many pounds of chemical per day does this dose represent?

43.7 lb/day

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364.3 lb/day

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261.3 lb/day

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3,643 lb/day

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With one secondary clarifier out of service, 1,330,000 gpd passes over the remaining 1,520 sq ft of clarifier surface. The operator is judging whether the peak can be held or must be shaved. What is the surface overflow rate?

700 gpd/sq ft

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1,050 gpd/sq ft

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875 gpd/sq ft

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1,400 gpd/sq ft

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Effluent solids have risen steadily over three shifts toward the discharge limit, traced to a clarifier upset that is now being corrected. Equalization storage with spare capacity is available upstream of discharge. What is the best effluent-disposal decision?

Discharge at full rate until the limit is actually exceeded

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Dilute the effluent with plant water at the outfall to lower the measured solids concentration, and continue discharging at the full permitted flow rate

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Discharge the poorest effluent at night when fewer people see it

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Temporarily hold or reduce discharge using the available storage while the clarifier recovers, releasing the stored effluent once quality returns

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When biosolids are land applied at agronomic rates, what primarily limits how much can be applied to a field?

The total volume of storage the farm has available that season, since chemical and energy costs are treated as secondary concerns here

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The number of truck trips the hauler can make in one day, because that response has worked at this plant in past seasons

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The nitrogen the crop can use, so application does not exceed crop nutrient need

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The phosphorus already present in the receiving stream nearby, and let the following shift decide whether the change helped

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Two identical centrifugal pumps discharge into a common header. With both running, total flow is well short of twice the single-pump flow, and both pumps test healthy. What explains the shortfall?

As combined flow rises, system head rises with it, moving each pump back on its curve to a lower individual output

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One of the two pumps must be rotating backwards whenever both pumps are running together on the common discharge header

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Parallel pumps can never add flow to a header

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The header gauge is the only thing that changed

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Two parallel mechanically cleaned bar screens serve one channel. Screen 1 rakes three times as often as Screen 2 and shows a higher upstream level, while total plant flow is steady. What is the best optimization move?

Take Screen 2 out of service to force all flow through Screen 1 according to the trend recorded over the past several operating shifts

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Slow the rake on Screen 1 to match Screen 2

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Rebalance the split so both screens share the flow and debris load more evenly

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Raise the rake speed on Screen 2 only

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A dissolved air flotation recycle pump must deliver 960 gpm against 144 ft of head. The pump efficiency at this duty is 80%. What brake horsepower must the motor supply?

34.91 hp

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43.64 hp

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27.93 hp

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54.55 hp

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What role do written laboratory standard operating procedures play in producing defensible data?

So every analyst works the same documented way, making results reproducible and traceable

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They encourage each analyst to improvise an individual technique for routine tests

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They replace the need for the laboratory to run any quality control samples, standards, or duplicates with its routine batches

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They are written only to satisfy safety inspections and are not used in analysis

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A plant-wide metals balance shows effluent metals low and steady, influent metals gradually rising, and sludge metals rising in step with influent. What does the balance demonstrate?

The metals are being destroyed by biological treatment by the biological treatment process and converted to harmless gases in the aeration basins

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The effluent metals results must be wrong

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Metals pass through the plant unchanged in the effluent

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The metals are being removed from the water by accumulation in the solids, so sludge quality and source control need attention

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A monthly maintenance report lists 400 total completed work orders, of which 190 were preventive maintenance work orders. What percent of the work orders were preventive maintenance?

47.5%

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52.5%

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21.0%

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2.1%

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A digester shows grit and foam accumulating, dead zones suspected, and gas production falling. Two mixing systems are proposed for replacement. How should performance data guide the choice?

Choose the system with the lowest purchase price, since mixing performance cannot be judged until it is installed

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Compare verified mixing performance at the digester's size and duty, since restoring full-volume mixing addresses the failure

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Choose the system whose motor is largest, because motor size alone guarantees the whole tank contents will move

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Keep the existing mixers and raise the feed rate, since more feed will stir the tank through gas production alone

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Wastewater Treatment Class III Exam Prep FREE Sample Exam — Fixed Set

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