Why pre-screen wastewater treatment engineers before the technical panel and plant site visit
Pre-screening wastewater treatment engineers saves your panel from candidates who have only read about the process. Applicants arrive from municipal operations, design consultancies, industrial pretreatment, and equipment vendors, and a resume listing MBR, BNR, and SCADA cannot tell you whether they sized the aeration basin or just reviewed someone else's drawings. A ten minute screen shows whether they can state design flows, permit limits, MLSS targets, and what happened to effluent quality after startup.
What actually matters when screening Wastewater Treatment Engineer candidates
- 01
Technical depth
Probe process depth: biological treatment stages, hydraulics, sludge handling, and the discharge limits they design against.
- 02
Work that shipped
Look for plants they designed, commissioned, or optimised, with flow rates and compliance results attached.
- 03
Diagnosis under uncertainty
Test how they respond when effluent quality drifts and the biology is the suspect but not the proof.
- 04
Working across the org
Check how they work with operators, regulators, and the public when a plant is failing consent.
Pre-screening questions to ask Wastewater Treatment Engineer candidates
12 questions grouped by what they test. Ask the same set in every screen and score answers on a consistent scale, or send them as an async video screen and compare answers side by side.
Process depth
4 questions01What methods have you used for biological nutrient removal, and what effluent nitrogen and phosphorus numbers did you hit?
Listen forNamed configurations (A2O, Bardenpho, MLE, SBR) with anoxic zone sizing, internal recycle rates, carbon dosing, and actual total nitrogen and phosphorus results in mg/L.
They list nutrient removal acronyms but cannot state a target limit, a recycle rate, or any measured effluent value.
02Walk me through your experience with sludge management and disposal, from thickening to final destination.
Listen forA full chain: WAS thickening, dewatering equipment (belt press, centrifuge, screw press), polymer dosing, cake solids percentage, and disposal route such as land application or incineration.
Sludge is treated as an afterthought, with no dewatering equipment named and no idea where the biosolids actually went.
03How familiar are you with anaerobic digestion, including loading rates and biogas handling?
Listen forDetail on mesophilic versus thermophilic operation, volatile solids loading, HRT, VFA to alkalinity monitoring, and what they did with the biogas (CHP, flare, upgrading).
They describe digestion only in textbook terms and cannot explain what a souring digester looks like or how they would recover it.
04What types of membranes have you worked with in MBR systems, and how did you manage fouling?
Listen forSpecific module types (hollow fibre, flat sheet) and suppliers, plus flux rates, permeability trends, relaxation and backpulse cycles, and maintenance versus recovery cleaning chemistry.
They claim MBR experience but cannot discuss flux, transmembrane pressure, or any cleaning-in-place regime they ran.
Projects delivered
3 questions05Pick one wastewater treatment facility you designed, upgraded, or commissioned and walk me through it: design flow, permit limits, and how it performed.
Listen forConcrete plant details: design flow in MGD or m3/d, their specific scope, permit limits for BOD, TSS and ammonia, and post-startup compliance results.
They describe the project only at a team level and cannot say which calculations, drawings, or startup tasks were theirs.
06Which software tools do you use for wastewater process design and hydraulic analysis?
Listen forNamed tools they used hands-on, such as BioWin or GPS-X for process modelling, SewerGEMS or InfoWorks for hydraulics, plus AutoCAD or Revit and Excel mass balances.
They name modelling packages they have only seen demonstrated, or cannot explain what they calibrated a model against.
07What strategies have you used to cut energy use at a treatment plant, and what did you actually save?
Listen forMeasures tied to numbers: turbo blower replacement, DO-based aeration control, VFDs on pumps, sidestream treatment, biogas CHP, with kWh per million gallons or percentage reduction.
Energy talk stays at the level of efficiency slogans with no baseline measurement or verified saving.
Diagnosis under pressure
3 questions08Effluent ammonia starts climbing over three days and you suspect the biology. How do you troubleshoot it?
Listen forA structured check: influent loading and toxicity, DO profile, SRT and MLSS trend, pH and alkalinity, temperature, microscopy, plus what they change first and how they verify it.
They jump straight to a fix such as adding chemicals without checking loading, DO, alkalinity, or recent process changes.
09How do you investigate and resolve odour complaints at a treatment facility?
Listen forH2S monitoring and dispersion thinking, source tracing to headworks, primaries or sludge storage, and controls such as covers, biofilters, carbon, or chemical dosing in the collection system.
They treat odour purely as a public relations problem rather than a measurable process and hydraulic condition.
10Describe a risk assessment you conducted for a treatment plant and what you changed as a result.
Listen forA real exercise: HAZOP or failure mode review on chlorine, methane or confined spaces, redundancy and bypass scenarios, and a specific design or procedural change that followed.
Risk assessment is described as a form they filled in, with no hazard identified and no action taken.
Stakeholders and compliance
2 questions11Tell me about a time a plant was at risk of breaching its discharge consent. How did you work with operators and the regulator?
Listen forEarly self-reporting, a corrective action plan with dates, daily monitoring, and evidence they worked alongside operators rather than issuing instructions from the office.
They blame operators or the regulator, or describe hiding the excursion until sampling forced disclosure.
12On a large plant upgrade, how do you keep designers, contractors, and operations staff aligned?
Listen forPractical mechanisms: operator input during design reviews, sequencing so treatment stays compliant during construction, commissioning plans, O&M handover, and training for plant staff.
They describe coordination only through documents and meetings, with no involvement of the operators who inherit the plant.
How to score responses
Score every candidate on the same four criteria immediately after the screen. At this stage you are shortlisting for panel interviews, not making the final call.
Technical depth
35%5Explains treatment biology and hydraulics in depth, and the discharge consents they designed against.
Work that shipped
30%5Names plants they designed or optimised, with flow, energy, or compliance results they owned.
Diagnosis under uncertainty
20%5Diagnoses process upsets methodically, distinguishing biological, hydraulic, and instrumentation causes.
Working across the org
15%5Works well with operators and regulators during a consent failure, and documents decisions defensibly.
Async video lets you hear a wastewater engineer talk through a P&ID or plant layout on screen, and see whether they explain an excursion calmly to operators or default to blame.
Try it on HirevireScreening FAQ
Process basics
What should a wastewater treatment engineer screening call cover in ten minutes?
Cover four areas: one biological process they know in detail (BNR, activated sludge, or anaerobic digestion), one plant they delivered with flow rate and permit limits, one troubleshooting story where effluent drifted, and their PE licence or EIT status plus travel tolerance for site work. Skip broad tool lists until the technical panel.
Do I need a PE licence requirement in the screen?
Ask about it early if the role stamps drawings or signs permit submittals, since a licensed Professional Engineer is legally required for that in most US states. For operations support or process optimisation roles, an EIT plus operator certification (Grade III or IV) can matter more than the stamp.
Evaluating answers
How do I judge process depth if I am not an engineer myself?
Listen for numbers and units rather than acronyms. Strong candidates name design flow in MGD or m3/d, MLSS in mg/L, SRT in days, permit limits for BOD, TSS, ammonia and total phosphorus, and what they adjusted when a number moved. Vague answers stay at the process-name level with no values.
What separates real commissioning experience from design-only experience?
Commissioning experience comes with startup detail: seed sludge sourcing, how long the nitrifiers took to establish, blower and DO setpoint tuning, punch lists, and the first compliance sampling results. Design-only candidates describe deliverables (basis of design, 30 percent drawings) but cannot say how the plant behaved once it was wet.
Go deeper on this role
Sanat has been hiring since 2012 and watching the recruitment industry change up close ever since, and turned that screening process into Hirevire's video screening platform. LinkedIn
