18 Safety, Security & Administration Practice Questions & Answers

1. 1. Before a permit-required entry into a wet well, the atmosphere is tested with a calibrated direct-reading instrument. In what order must it be tested?

   • A.Oxygen first, then flammable gases, then toxic contaminants✓ Answer
   • B.Flammable gases first, then oxygen, then toxic contaminants
   • C.Toxic contaminants first, then oxygen, then flammable gases
   • D.Oxygen first, then toxic contaminants, then flammable gases

   A catalytic (hot-wire) combustible-gas sensor must burn the sample to produce a reading, so it reads falsely low or fails outright in oxygen-deficient air. Oxygen is therefore tested first so the operator knows whether the flammable reading that follows can be trusted; testing is done from outside the space at top, middle and bottom because gases stratify by density.

   Source: OSHA 29 CFR 1910.146(c)(5)(ii)(C) atmospheric testing sequenceReport a problem with this question

2. 2. A crew is preparing to enter a digester gallery dry well. Who authorizes the entry by signing the entry permit?

   • A.The authorized entrant, before descending into the space
   • B.The attendant, after taking post outside the opening
   • C.The rescue service leader, after checking the equipment
   • D.The entry supervisor, after verifying tests and controls✓ Answer

   The entry supervisor is the role that verifies all required tests, isolation and controls are complete and then signs the permit, and the same person terminates entry when the work is done or a prohibited condition appears. The attendant and entrant have duties under the permit but no authority to authorize entry.

   Source: OSHA 29 CFR 1910.146(e)(2) and (j), entry supervisor dutiesReport a problem with this question

3. 3. An attendant watching a manhole entry sees the entrant slump against the wall and stop responding. What should the attendant do?

   • A.Wait at the opening for the entry supervisor to arrive first
   • B.Enter wearing a harness and lifeline to pull the entrant out
   • C.Enter with an air-purifying respirator and a second lifeline
   • D.Summon rescue and attempt retrieval from outside the space✓ Answer

   The attendant must never leave the post to enter the space; a large share of confined-space deaths are untrained would-be rescuers overcome by the same atmosphere. The correct response is to call the rescue service, order any other entrants out, and use the retrieval line and mechanical device to perform non-entry rescue from outside.

   Source: OSHA 29 CFR 1910.146(i)(6) attendant duties; (k)(3) non-entry retrievalReport a problem with this question

4. 4. An entrant in a wet well reports a strong rotten-egg odor, then radios a few minutes later that the smell has gone away. How should this be interpreted?

   • A.The gas dissolved into the wastewater and the reading will drop
   • B.The gas has dispersed and the space has become safer to occupy
   • C.The meter's toxic sensor has drifted and needs to be re-zeroed
   • D.The gas has deadened his sense of smell and the danger is greater✓ Answer

   Hydrogen sulfide paralyzes the olfactory nerve at concentrations well below those that cause collapse, so the loss of odor signals rising, not falling, concentration. Smell is never a warning device for H2S; the entrant should be ordered out immediately and the atmosphere re-tested with a calibrated instrument.

   Source: NIOSH/OSHA hydrogen sulfide hazard guidance; CSUS Operation of Wastewater Treatment Plants, Vol. 1, safety chapterReport a problem with this question

5. 5. An operator has locked and tagged the disconnect for a return sludge pump and bled the discharge line. What must be done before maintenance work begins?

   • A.Try to start the pump at its normal controls, then return them to off✓ Answer
   • B.Record the lock number in the maintenance log and tell the shift lead
   • C.Hang a second warning tag at the motor control center as a backup
   • D.Have a coworker confirm the wording on the tag before work starts

   Verification of isolation is the step most often skipped and is required before service: the authorized employee attempts to operate the equipment from its normal controls, confirms it will not start, and returns the controls to the off position, along with testing for zero energy. Logging, extra tags and peer checks are good practice but none of them proves the energy is actually isolated.

   Source: OSHA 29 CFR 1910.147(d)(6) verification of isolationReport a problem with this question

6. 6. A maintenance job runs past the end of shift and one worker's lock is still on the group lock box. Who is permitted to remove that lock?

   • A.The shift supervisor at the end of every operating shift
   • B.Any authorized employee on the crew once the work is finished
   • C.Only the authorized employee who applied that particular lock✓ Answer
   • D.The maintenance lead once the guards have been reinstalled

   Each authorized employee applies his or her own lock, and only that person may remove it, because the lock is what guarantees no one energizes equipment while that worker is still exposed. The employer may remove a lock in the worker's absence only under a documented procedure that includes reasonable efforts to notify the employee before work resumes.

   Source: OSHA 29 CFR 1910.147(e)(3) lockout device removalReport a problem with this question

7. 7. A new coagulant is delivered and the operator needs to know what gloves and eye protection are required before handling it. Which safety data sheet heading gives that information?

   • A.Exposure controls and personal protection✓ Answer
   • B.Stability and reactivity information
   • C.Handling and storage requirements
   • D.Physical and chemical properties data

   The exposure controls and personal protection heading is where the SDS lists occupational exposure limits, required engineering controls, and the specific glove, eye and respiratory protection for that product. Handling and storage covers safe work practices and incompatible storage, while first-aid and spill instructions appear under their own separate headings.

   Source: OSHA 29 CFR 1910.1200 Appendix D, SDS section on exposure controls/personal protectionReport a problem with this question

8. 8. An operator smells chlorine near a ton container manifold and must locate the leaking joint. What is the correct field test?

   • A.Flush the joint with plant water and watch for bubbling
   • B.Hold a swab wetted with aqueous ammonia near the joint✓ Answer
   • C.Coat the joint with soapy water and look for foaming
   • D.Wave a wetted litmus paper strip through the vapor

   Ammonia vapor reacts with escaping chlorine to form a visible white cloud of ammonium chloride, which pinpoints the leak without disturbing it. Water must never be applied to a chlorine leak: chlorine and water form acids that corrode the container and rapidly enlarge the opening, and soap or litmus methods are unreliable for this gas.

   Source: Chlorine Institute leak-detection practice; CSUS Operation of Wastewater Treatment Plants, Vol. 1, chlorination safetyReport a problem with this question

9. 9. A guardrail section has been removed from an elevated clarifier walkway so an operator can service a skimmer arm. What fall protection is required for that work?

   • A.A warning line set back from the edge with posted signs
   • B.A retractable lifeline clipped to the handrail stanchion
   • C.A full-body harness and lanyard tied to a rated anchorage✓ Answer
   • D.A body belt and lanyard tied to the same rated anchorage

   When guardrails are not in place, a personal fall arrest system is required, and it must use a full-body harness that distributes arrest forces across the thighs, pelvis, chest and shoulders. Body belts are prohibited for fall arrest because they concentrate the force on the abdomen, a handrail stanchion is not a rated anchorage, and warning lines do not arrest a fall.

   Source: OSHA 29 CFR 1910.140(c)(15) body belts prohibited for fall arrest; 1910.28 Subpart DReport a problem with this question

10. 10. A portable four-gas meter is taken from the charger at the start of the shift for a day of manhole checks. What must the operator do with it before use that day?

    • A.Perform a full span calibration against certified gas standards
    • B.Check the battery and the date of the last recorded calibration
    • C.Zero it in fresh air at the opening of the first space entered
    • D.Bump test it with known gas to confirm the sensors respond✓ Answer

    A bump test applies a known challenge gas to confirm every sensor responds and the alarms activate, and it is required before each day's use because a sensor can fail silently between calibrations. Full calibration is done on the manufacturer's schedule or after a failed bump test, and fresh-air zeroing must be done in air known to be clean, not at the opening of a space that may be venting contaminants.

    Source: OSHA 29 CFR 1910.146 App B and instrument manufacturer/ANSI practice: bump test before each day's useReport a problem with this question

11. 11. A plumbed emergency eyewash and shower is installed at the chemical feed area. What routine maintenance does the unit require?

    • A.Activation whenever a bulk chemical delivery is received
    • B.Activation every month with the water temperature logged
    • C.Activation every week to flush the line and verify flow✓ Answer
    • D.Inspection each year when the fire extinguishers are serviced

    Plumbed units are activated weekly so stagnant water and any microbial growth are flushed out of the dead-leg supply line and so the operator confirms the valve opens and stays on hands-free. A full performance inspection is done annually, but an annual check alone would leave a plugged or dry unit undiscovered when an operator needs a fifteen-minute flush.

    Source: ANSI/ISEA Z358.1 weekly activation of plumbed eyewash and shower equipmentReport a problem with this question

12. 12. A drum of sodium hypochlorite is leaking onto the floor of the chemical room. The operator on duty is trained only to the awareness level. What is the correct first action?

    • A.Dike the spill with absorbent from the kit outside the room
    • B.Neutralize the hypochlorite with acid stored on the same rack
    • C.Warn others, leave and isolate the area, notify the supervisor✓ Answer
    • D.Wash the spill toward the floor drain with plant service water

    Life safety comes before property or process: the awareness-level employee is trained to recognize the release, protect people by evacuating and isolating, and notify, but not to perform offensive containment or cleanup. Washing the spill to a drain sends the chemical into the process, and mixing hypochlorite with acid liberates chlorine gas.

    Source: OSHA 29 CFR 1910.120(q)(6)(i) first-responder awareness level dutiesReport a problem with this question

13. 13. A utility wants its nightly security rounds of the plant to satisfy the intent of a routine security check. What most distinguishes a proper routine check?

    • A.It is a drive-through of the site made whenever staff have time
    • B.It follows a set schedule and the findings are written in a log✓ Answer
    • C.It is a gate and lock check performed after an alarm has sounded
    • D.A camera recording review carried out at the end of a month

    A routine security check is a scheduled, documented round of gates, fences, lighting, hatches, chemical storage and alarm status, and the written record is what makes trends and tampering visible and supports follow-up. Checks made only when convenient or only after an alarm are reactive and leave no evidence that the site was inspected; suspicious activity is reported to the supervisor and law enforcement rather than confronted.

    Source: WPI 2025 Need-to-Know Criteria job task 'conduct routine security checks'; WEF/VSAT security guidanceReport a problem with this question

14. 14. A plant is reviewing the cybersecurity of the SCADA system that runs its aeration and disinfection controls. Which practice best protects plant operation?

    • A.Separate the control network from the business network and internet✓ Answer
    • B.Postpone software patching until the annual maintenance shutdown
    • C.Keep one shared operator login so alarms are never missed on shift
    • D.Allow direct internet access to the operator screens for on-call staff

    Segmenting the operational technology network from the business network and the public internet removes the most common attack path, since intrusions typically reach controls through email or office systems. Shared logins destroy accountability and survive employee departures, internet-exposed operator screens are directly attacked, and deferred patching leaves known vulnerabilities open all year; the plant must also retain the ability to run in manual if SCADA is lost.

    Source: WaterISAC/CISA water sector cybersecurity fundamentals; AWWA cybersecurity guidance for OT network segmentationReport a problem with this question

15. 15. An operator realizes that a flow reading entered in the daily operating log an hour ago was written down wrong. How should the entry be corrected?

    • A.Erase the error, write the correct value, and continue the day's entries
    • B.Draw one line through the error, write the correct value, initial and date✓ Answer
    • C.Cover the error with correction fluid and write the correct value over it
    • D.Leave the error alone and report the correct value on the monthly report

    The operating log is a legal record that may be used as evidence, so an error is lined out once, left readable, corrected, and initialed and dated to show who changed what and when. Erasing or covering an entry destroys the original record and makes the whole log look altered, which is why falsifying or back-filling records carries civil and criminal penalties and ends careers.

    Source: 40 CFR 122.41(j)(2) monitoring records; CSUS Operation of Wastewater Treatment Plants, Vol. 1, records and reportsReport a problem with this question

16. 16. A storm causes a partial bypass of the secondary process and effluent leaves the plant well above the permitted limits. What is the operator's obligation?

    • A.Report it only on the next discharge monitoring report with a note attached
    • B.Notify the permitting authority promptly and follow with a written report✓ Answer
    • C.Wait for a confirmation resample before notifying anyone outside the plant
    • D.Notify only if the following day's sample also exceeds the permitted limits

    Standard permit conditions require noncompliance that may endanger health or the environment to be reported orally as soon as the permittee becomes aware of it, with a written submission following a few days later, and the routine monthly report does not satisfy that duty. Waiting for a resample or for a second exceedance delays notice that the regulator needs while the discharge is still occurring, and some states impose stricter timing than the federal minimum.

    Source: 40 CFR 122.41(l)(6) twenty-four hour reporting of noncomplianceReport a problem with this question

17. 17. After a pump replacement, an operator finds that one step in the approved SOP can no longer be performed safely on the new unit. What should the operator do?

    • A.Follow the SOP exactly as written because it is the approved document
    • B.Stop, report it, and have the SOP revised through the review process✓ Answer
    • C.Do the step the safest way he can and tell the next shift about it
    • D.Cross the step out in the binder and write the new procedure beside it

    An SOP is a controlled document, so a step that has become unsafe or impossible is corrected by stopping work, reporting it, and putting the change through the review and approval process that produces a new revision for every copy and every shift. Improvising, forcing the old step, or hand-editing the binder leaves shifts working from different procedures and destroys the version control that training and consistency depend on.

    Source: WPI 2025 Need-to-Know Criteria job tasks 'adhere to SOPs' and 'establish and/or update SOPs'; CSUS Vol. 1Report a problem with this question

18. 18. For the monthly operating report, influent BOD averaged 240 mg/L and effluent BOD averaged 18 mg/L at an average flow of 2.5 MGD (9.5 ML/d). What BOD removal is reported?

    • A.92.5 percent✓ Answer
    • B.88.0 percent
    • C.7.5 percent
    • D.90.0 percent

    Percent removal is the mass or concentration removed divided by what came in: (240 - 18) / 240 x 100 = 92.5 percent. The flow is not needed and is there as a distractor, since both concentrations share the same flow; dividing the effluent by the influent instead gives 7.5 percent, which is the fraction remaining, not the fraction removed.

    Source: Percent removal formula, WPI Formula/Conversion Table; 40 CFR 133.102 secondary treatment 85 percent removal requirementReport a problem with this question

Practice questions written against the 2025 standardized Wastewater Treatment Operator Need-to-Know Criteria published by Water Professionals International (formerly the Association of Boards of Certification) and standard references from the CSUS Office of Water Programs and the Water Environment Federation. This site is not affiliated with or endorsed by WPI/ABC, WEF, or the US EPA. Operator certification is issued by your state's certifying authority, which sets plant classification tiers, operator grades, eligibility, and the passing standard — confirm those with your state before testing, and confirm which edition of the exam your program has adopted. Effluent limits, monitoring frequencies and reporting requirements come from an individual discharge permit and are revised over time, so no answer here should be relied on as a current regulatory or permit value; consult the permit in force for your facility. This bank covers the wastewater treatment exam only — drinking-water treatment, water distribution, and wastewater collection are separate certifications. About the Need-to-Know Criteria →