NV Water/Wastewater Operator key terms

The rapid mixing of a chemical such as alum into raw water so that tiny suspended particles destabilize and begin to clump together. It is the first step of conventional filtration and is followed by flocculation.

Gentle, slow stirring of chemically treated water that encourages destabilized particles to collide and grow into larger, settleable clumps called floc. It follows coagulation and precedes sedimentation.

A gravity process in which water sits quietly in a basin long enough for heavier suspended solids and floc to settle to the bottom as sludge. Also called clarification when paired with chemical treatment.

Passing water through a bed of sand, anthracite, or other media to trap remaining particles, including protozoan cysts, after settling. It is a physical barrier and typically the final particle-removal step before disinfection.

Reversing flow upward through a filter bed at a rate high enough to lift and scrub the media, flushing trapped solids to waste. Operators trigger it on headloss, turbidity, or run time and must return the filter to service properly.

The cloudiness of water caused by suspended particles that scatter light. Measured in nephelometric turbidity units, it is a key indicator of filtration performance and a required monitoring parameter for pathogen control.

A laboratory or online instrument that measures turbidity by detecting light scattered at an angle by particles in a sample. Proper calibration and sample handling are essential because readings drive regulatory compliance decisions.

Inactivating disease-causing microorganisms in treated water, usually with chlorine, chloramine, ozone, or ultraviolet light. It differs from sterilization because it does not necessarily kill every organism present.

The product of disinfectant concentration (C) and contact time (T) used to demonstrate that a required level of pathogen inactivation has been achieved. CT requirements vary by disinfectant, target organism, temperature, and pH.

The concentration of chlorine still present in water after treatment, reported as free or total chlorine. A detectable residual protects against contamination in the distribution system and is a required monitoring value.

Chemicals such as trihalomethanes and haloacetic acids that form when disinfectants react with naturally occurring organic matter. Operators manage them by controlling precursor organics and balancing disinfection against byproduct formation.

A measure of the organic material in water that can react with disinfectants to form byproducts and contribute to color, taste, and odor. Removal is tracked across coagulation and filtration to judge treatment effectiveness.

A bench-scale simulation in which several beakers of raw water receive different coagulant doses and mixing speeds, so the operator can select the dose and conditions that produce the best floc and settled clarity.

Adjusting an instrument so its readings agree with a known standard, then documenting the result. Regular calibration of turbidimeters, chlorine analyzers, pH meters, and flow meters underpins trustworthy compliance data.

Any actual or potential link between a potable water system and a source of nonpotable water or contamination. Preventing and controlling these links is central to protecting distribution system water quality.

Devices and practices that stop water from flowing backward into a potable system, such as air gaps, reduced-pressure zone assemblies, and vacuum breakers. Selection depends on the degree of hazard and local rules.

A public health advisory telling customers to boil water before drinking or cooking because the supply may contain pathogens. Operators issue it after pressure loss, treatment failures, or confirmed contamination and lift it only after testing clears the system.

A pressure surge caused by a sudden change in flow velocity, such as rapid valve closure or pump shutdown, that travels through piping as a shock wave. It can damage pipes and fittings and is controlled with slow-closing valves and surge protection.

A graphical line showing the pressure head plus elevation of water at points along a pipeline or system. Comparing it with pipe elevations reveals where pressures are adequate, excessive, or where flow will not occur.

An instrument that displays the pressure of water in a pipe or system, usually in psi or kPa. Operators use gauges to confirm pump performance, detect restrictions, and verify that service pressures stay within required ranges.

Deliberately running water through mains or hydrants to remove sediment, stale water, and biofilm and to restore disinfectant residual. Unidirectional flushing uses planned valve closures to increase scouring velocity.

The network of pipes, storage tanks, pumps, valves, and hydrants that delivers finished water from the treatment plant to customers. Maintaining pressure and disinfectant residual throughout it is a core operator duty.

A reservoir that holds treated water to meet peak demand, provide fire flow, and maintain pressure. Tanks need routine inspection, mixing, and turnover to prevent stagnation, sediment buildup, and loss of residual.

The wastewater entering a treatment plant or a specific treatment unit. Its flow rate and strength (BOD, TSS, ammonia) set the loading the process must handle and guide operational adjustments.

The treated water leaving a treatment plant or process unit, which must meet permit limits before discharge or reuse. Effluent monitoring results demonstrate whether the plant is performing as required.

The amount of dissolved oxygen microorganisms consume while breaking down organic matter in a sample over a set period, usually five days. It estimates organic strength and is a common permit limit for effluent.

The concentration of solid particles suspended in water or wastewater, determined by filtering a sample, drying it, and weighing the residue. It is a primary permit parameter and a gauge of treatment and settling performance.

Supplying air or oxygen to wastewater so aerobic bacteria can oxidize organic matter and ammonia. Operators control blower output and dissolved oxygen levels to keep the biological process healthy without wasting energy.

A biological treatment process in which a mixed community of microorganisms is kept suspended in aerated wastewater and then separated in a clarifier, with settled biomass returned to the aeration basin to treat more flow.

The concentration of suspended solids, mostly microorganisms, in the aerated mixed liquor of an activated sludge basin. It is used with other data to calculate solids inventory and the food-to-microorganism ratio.

Settled biological solids collected from the clarifier bottom and pumped back to the aeration basin to maintain the microorganism population needed for treatment. The return rate is adjusted to control solids inventory.

Excess biological solids deliberately removed from the activated sludge system to control solids retention time and prevent overloading the clarifiers. Wasting rate is a primary lever for managing sludge age.

The average time biological solids remain in the treatment system before being wasted, also called sludge age or mean cell residence time. It strongly influences nitrification, settling, and effluent quality.

The mass of organic food entering the aeration basin divided by the mass of microorganisms present, often expressed as F/M. It indicates whether biomass is underloaded or overloaded and helps predict sludge settling behavior.

The concentration of oxygen dissolved in water, critical for aerobic treatment and for aquatic life in receiving streams. Low levels in an aeration basin can cause poor treatment, odors, and settling problems.

The biological conversion of ammonia to nitrite and then nitrate by specialized bacteria. It consumes large amounts of oxygen and alkalinity and is sensitive to cold temperatures and short solids retention times.

The biological conversion of nitrate to nitrogen gas under low-oxygen conditions, often used to meet total nitrogen limits. If it occurs in a clarifier, the released gas can float sludge and degrade effluent quality.

A settling tank that separates solids from liquid, either as primary clarification ahead of biological treatment or as secondary clarification after it. Operators watch sludge blankets and weirs to prevent solids carryover.

The layer of settled solids at the bottom of a clarifier. Its depth and clarity indicate whether sludge is being returned or wasted at the right rate and whether solids are at risk of washing over the weirs.

The solids removed from wastewater during treatment, including primary and waste biological solids. Handling, thickening, dewatering, and disposal of sludge are major operational costs and regulatory responsibilities.

Extraneous water entering a collection system through groundwater seepage (infiltration) or direct connections such as storm drains and sumps (inflow). It adds flow that can overload pipes and treatment units during wet weather.

An unauthorized release of untreated sewage from a collection system, often during blockages or wet-weather overloads. Operators must respond quickly, contain and report the spill, and address the underlying cause.

The network of gravity sewers, lift stations, force mains, and manholes that carries wastewater from homes and businesses to the treatment plant. Its condition and capacity directly affect plant flows and overflow risk.

A facility with pumps that raise wastewater to a higher elevation so it can continue by gravity. Reliable operation, wet-well level control, and backup power are essential to prevent overflows.

The federal permitting program that sets limits and monitoring requirements for wastewater discharged to surface waters. Each plant's permit defines allowable effluent concentrations, reporting, and compliance schedules.