Wastewater Treatment Class I Exam Prep FREE Sample Exam

Why is wastewater effluent dechlorinated before discharge to surface water?

Because chlorine residual is toxic to aquatic life

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Because chlorine residual makes the effluent too clear to sample accurately

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Because dechlorination restores dissolved oxygen consumed in the aeration basin

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Because chlorine must be recovered and reused in the headworks chemical tank

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Digested sludge shows a much lower percent volatile solids than the raw sludge fed to the digester. What does this indicate?

The digester added organic matter to the sludge while it was being stored

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Percent volatile rises whenever digestion is working as it should perform

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The laboratory ignition step created new volatile solids in the dried sample

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Digestion destroyed a portion of the organic solids

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Sludge on a drying bed drains very slowly and stays wet on top after several days. What is a likely process cause to investigate?

Blinded bed media or clogged underdrains that are slowing drainage through the bed

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Excess grit lightening the sludge

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Too much chlorine in the effluent

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Uneven sunlight on the bed surface

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A contact basin operates with a chlorine residual of 1.4 mg/L and provides 25 minutes of contact time. What is the CT value?

26.4 mg-min/L

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3.5 mg-min/L

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350 mg-min/L

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35 mg-min/L

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A progressing-cavity pump feeding sludge to a press has lost output over several weeks. Discharge pressure pulsates, the suction supply is good, and the drive speed has not changed. What should the operator suspect?

Worn stator and rotor surfaces are letting sludge slip back inside the pump instead of moving forward with each turn

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The polymer conditioning system has failed, which prevents a positive displacement pump from moving any sludge at all

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The drive motor is running far above its rated speed, which makes this type of pump deliver less sludge per revolution

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The discharge line is completely blocked solid, which normally makes this pump run quietly with a smooth, low output

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What is the main operational difference between coarse-bubble and fine-bubble diffusers?

Coarse-bubble diffusers are used only in grit chambers and are never used in aeration basins

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Fine-bubble diffusers never require cleaning during their service life

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Coarse-bubble diffusers transfer oxygen more efficiently than fine-bubble units

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Fine-bubble diffusers make smaller bubbles and transfer oxygen more efficiently

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What does the unloader valve on a plant air compressor do?

It raises the receiver pressure above the compressor's rated limit so the stored air can do more work before the compressor has to restart and refill the receiver tank again

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It relieves pressure from the compressor head at shutdown or cut-out so the motor can restart without fighting trapped pressure

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It drains condensed water from the receiver tank on a timed cycle

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It filters oil out of the compressed air before the air dryer unit

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During rounds, an operator hears a grinding noise from a motor that was quiet last week, and the bearing housing feels hotter than usual. What is the best response?

Report it and schedule bearing inspection soon

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Wait a few months to see if the noise goes away

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Add extra grease until the housing overflows out

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Run the motor faster so the noise blends in well

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What is the purpose of the silencer on a blower’s air inlet?

To filter grit and sand out of the air before it reaches the basin

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To cool the incoming air so the blower discharge stays at setpoint

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To reduce the intake noise produced as air is drawn into the blower

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To measure the volume of air the blower delivers to the aeration grid

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Influent TSS is 200 mg/L and effluent TSS is 30 mg/L. What is the percent removal across the plant?

15 percent removal based only on the effluent value divided by the influent value alone

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170 percent removal across the plant

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70 percent removal across the plant

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85 percent

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After locks and tags are applied to a pump’s energy sources, what final lockout/tagout step confirms the equipment is safe to service?

Removing the lock so the start switch can be tested freely

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Trying the controls and checking that no stored or residual energy remains

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Asking a coworker who watched the shutdown whether it looked complete and taking their word for it without checking anything yourself

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Signing the work order to show the job is ready to begin

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Where should a worker look for hazard and safe-handling information on a laboratory chemical?

On the product marketing sheet kept in the front office reception area drawer

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In the monthly discharge monitoring report filed for the treatment facility

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In the safety data sheet for that chemical

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On the shipping invoice that lists only the price and delivery date information

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

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