OR Water/Wastewater Operator key terms

A measure of how cloudy water is, caused by suspended particles that scatter light. High turbidity can hide pathogens from disinfection and interfere with treatment processes such as filtration.

The water's capacity to neutralize acid, coming mostly from bicarbonate, carbonate, and hydroxide. It buffers pH changes and is important for effective coagulation and for corrosion control.

The concentration of dissolved calcium and magnesium in water, usually reported as calcium carbonate equivalents. Hard water forms scale in pipes and water heaters and reduces soap lathering.

A group of bacteria used as an indicator of treatment effectiveness and possible contamination. Their presence suggests the water may contain pathogens from soil or fecal material.

The amount of carbon bound in organic compounds in the water. Organic matter feeds disinfection byproduct formation and can foul filters, so utilities track and remove it.

Adding a chemical such as alum or ferric chloride to water so that small particles clump together. The chemical neutralizes the electrical charges that keep particles apart.

Gentle, slow mixing that encourages small particles to collide and grow into larger, heavier clumps called floc, which can then be settled or filtered out.

A bench-scale procedure that mixes beakers of raw water with different coagulant doses and mixing conditions to find the best treatment settings before full-scale operation.

A physical process in which water sits in a basin long enough for heavier particles and floc to settle to the bottom, producing clearer water and a sludge layer.

Reversing water flow through a filter to lift and expand the media, washing out trapped particles. It restores filter capacity and is followed by rinsing before returning to service.

Adding lime to raise pH and precipitate calcium and magnesium as solids that settle out. Excess lime is then neutralized and the water stabilized to prevent scale in pipes.

Any actual or potential link between the drinking water system and a source of contamination. Backflow devices and routine inspections prevent pollutants from being drawn into the pipes.

The time water spends traveling from treatment through pipes and storage to the consumer. Older water can lose disinfectant residual and form more disinfection byproducts.

How quickly the volume of a distribution storage tank is replaced by incoming flow. Poor turnover raises water age and can degrade disinfectant residual and taste.

Groundwater and stormwater that enter a sanitary sewer through cracks, joints, manholes, and illegal connections. It adds flow that pipes and treatment plants must handle.

A release of untreated sewage from the collection system before it reaches the treatment plant, often during blockages or wet weather. Overflows are reportable and pose public health risks.

A facility with pumps and a wet well that raises wastewater to a higher elevation so it can continue flowing downhill by gravity toward the treatment plant.

A settling tank near the start of a wastewater plant that removes settleable solids and floating material, producing primary sludge and reducing the load on downstream biological treatment.

A biological treatment process in which a mixed community of microorganisms consumes organic matter in aerated wastewater. The biomass is settled and mostly returned to keep the process going.

The concentration of suspended solids, mostly microorganisms, in the aerated tank of an activated sludge plant. It is used to set wasting rates and calculate loading.

A test result showing how well activated sludge settles, calculated from the settled volume of a sludge sample and its suspended solids concentration. High values warn of bulking.

The pounds of organic food entering the aeration tank divided by the pounds of microorganisms present. Operators use it to control wasting and keep treatment stable.

A two-step biological process in which bacteria convert ammonia to nitrite and then to nitrate, consuming oxygen and alkalinity. It matters for ammonia limits and nutrient removal.

A process in which bacteria break down sludge in the absence of oxygen, reducing solids and producing biogas. It stabilizes biosolids and reduces odors.

Treated wastewater solids that meet regulatory standards and can be beneficially reused, for example as a soil amendment or fertilizer. Reuse depends on pathogen and metal limits.

The product of disinfectant residual concentration and contact time, used to measure how effective disinfection is against a target organism. A higher CT means more inactivation.

The amount of chlorine still available to kill organisms after demand has been satisfied. It is measured in the field to confirm that distribution systems remain protected.

Compounds such as trihalomethanes and haloacetic acids that form when disinfectants react with natural organic matter. Utilities control them by removing precursors and adjusting treatment.

A disinfectant formed by combining chlorine with ammonia. It lasts longer in pipes than free chlorine but is weaker and needs careful control to avoid nitrification problems.

Using ultraviolet light to damage the genetic material of pathogens so they cannot reproduce. It works without adding chemicals but leaves no lasting residual in the water.

A sample made by combining several portions collected over time or across a flow, giving an average picture of water or wastewater quality. Flow-weighted versions are common at plants.

A written record tracking who collected, handled, and analyzed a sample, and when. It keeps results legally defensible and shows the sample was not altered.

The amount of oxygen microorganisms consume while breaking down organic matter in a sample held five days at 20 degrees Celsius. It estimates the organic strength of wastewater.

The average time water or wastewater spends in a tank or basin, calculated by dividing tank volume by flow rate. It is central to sizing and evaluating treatment units.

The enforceable limit on the concentration of a contaminant allowed in drinking water delivered to consumers. It is set by the regulatory agency based on health effects.

A permit that sets limits on the pollutants a wastewater discharge may contain and requires monitoring and reporting. It implements the Clean Water Act requirements.

A space large enough to enter, with limited entry or exit, that is not designed for continuous occupancy. It may hold hazardous atmospheres requiring testing and an entry permit.

A procedure for isolating energy sources such as electrical, mechanical, hydraulic, and pneumatic before servicing equipment, using locks and tags so machinery cannot start unexpectedly.