WA Water/Wastewater Operator key terms

Water taken from a source such as a river, lake, or well before any treatment. Its quality varies with season, weather, and upstream activity, and it sets the baseline for what the treatment plant must remove.

Water that has completed all treatment steps and is ready for distribution to customers. It must meet all primary drinking water standards at the point it leaves the plant.

The cloudiness of water caused by suspended particles like silt, clay, and organic matter. It is measured in nephelometric turbidity units and serves as both a treatment performance indicator and a health-related limit.

The concentration of minerals, salts, and other dissolved substances remaining after water is filtered. High levels affect taste and can indicate source water contamination or intrusion of saline water.

A group of bacteria used as an indicator of sanitation and possible pathogen contamination in drinking water. Their presence suggests treatment failure or distribution system problems rather than proving disease is present.

The process of adding a chemical such as alum or ferric chloride to neutralize particle charges so small suspended solids clump together. It is usually followed by gentle mixing and then settling.

Slow, gentle stirring after coagulation that encourages small particles to collide and grow into larger, heavier clumps called floc. Proper mixing time and energy are needed so the floc does not break apart.

A physical process in which heavier particles sink to the bottom of a basin under the influence of gravity. Also called sedimentation, it removes floc and grit before water moves on to filtration.

Reversing the flow of water upward through a filter to dislodge and carry away trapped particles. Backwash water is usually returned to the head of the plant or otherwise managed.

Chemicals such as trihalomethanes and haloacetic acids that form when disinfectants react with natural organic material in water. Their levels are regulated, so plants balance enough disinfection against excessive byproduct formation.

A measure of the carbon contained in dissolved and suspended organic matter in water. It is a key precursor to disinfection byproducts and is often monitored to judge how well treatment removes it.

The amount of chlorine remaining in water after it has been dosed, including both free and combined forms. It is measured to confirm that a protective disinfectant residual travels through the distribution system.

A calculation combining disinfectant concentration and contact time to express how much disinfection is delivered. Higher CT values mean more inactivation of pathogens such as Giardia and viruses.

A tank or series of baffled chambers that gives disinfectant enough time to work before water leaves the plant. Design and flow patterns determine the effective contact time used in CT calculations.

A pump or feeder that injects a chlorine solution, such as sodium hypochlorite, into water at a controlled rate. Operators adjust the feed rate to maintain the target residual.

A metering device that delivers a precise, adjustable volume of liquid chemical into a process stream. Accurate calibration is essential because small feed errors can cause large changes in water chemistry.

Any actual or potential link between a drinking water system and a source of nonpotable water or contamination. Backflow prevention devices and routine inspections are used to control this hazard.

The unwanted reverse flow of water or other liquids into a drinking water system. It can be caused by backpressure or back siphonage and is prevented with air gaps and check valves.

A physical separation between a water supply outlet and the highest possible level of a contaminating liquid. It is the most reliable form of backflow protection because it has no moving parts to fail.

A large pipe in the distribution system that carries water from the source or storage to smaller pipes serving streets and buildings. It is typically the backbone of the network and is often looped for reliability.

The pipe that carries water from the distribution main to a customer's property or building. Its size, material, and condition affect pressure and water quality at the tap.

A valved connection on a water main used for firefighting and sometimes for flushing or testing. Regular inspection and flushing help keep it operational and improve water quality in dead-end areas.

A planned method of opening selected hydrants and valves in sequence to push water through mains in one direction at high velocity. It scours sediment and stale water from pipes and improves chlorine residual.

A device that measures the volume of water delivered to a customer. Meter readings support billing and can reveal leaks or unusual consumption patterns when compared with historical use.

A pipe system that carries wastewater from homes and businesses to a treatment facility. It is kept separate from stormwater to reduce the volume and contamination reaching the plant.

Groundwater that seeps into sewers through cracks and joints, plus stormwater that enters through improper connections or manholes. High levels can overload collection systems and treatment plants during wet weather.

A single pipe that carries both sanitary sewage and stormwater runoff. During heavy rain it may overflow untreated into receiving waters, so many communities are separating or controlling these overflows.

A facility with pumps that raise wastewater to a higher elevation so it can continue flowing by gravity. Wet wells, level controls, and backup power are critical to prevent overflows.

A chamber that collects wastewater before it is pumped. Operators monitor its level and control pumps so the well neither overflows nor runs dry.

A valve that allows flow in only one direction and closes automatically when flow reverses. It protects pumps from backspin and prevents wastewater from returning to a wet well.

A pump that uses a spinning impeller to throw water outward and create pressure. It is the most common type in water and wastewater service and is best suited to moving large volumes at moderate pressures.

The formation and collapse of vapor bubbles in a pump when local pressure drops too low. It causes noise, vibration, and pitting damage, and is usually corrected by improving suction conditions.

The absolute pressure available at a pump's suction inlet above the liquid's vapor pressure. Too little of it leads to cavitation, so it must be checked when designing or troubleshooting pump installations.

A graph showing the relationship between a pump's flow rate and the head it produces. Operators use it with the system curve to find the operating point and select the right pump.

Comparing an instrument's reading against a known standard and adjusting it so the reading is accurate. Regular calibration of meters and feeders is essential for reliable process control and regulatory reporting.

A measure of how well water conducts electricity, which rises with dissolved mineral content. It is used to estimate dissolved solids and to detect changes in source water quality.

The solids removed from water or wastewater during settling and other treatment steps. It must be thickened, digested, dewatered, or otherwise handled before final disposal.

An enclosed area with limited entry and exit that is not designed for continuous occupancy, such as a manhole or wet well. Entry requires permits, atmospheric testing, ventilation, and a trained attendant.

A safety procedure that isolates energy sources and attaches locks and tags before equipment is serviced. It prevents accidental startup or release of stored energy that could injure workers.

An annual report that a water system must provide to its customers describing the quality of the water delivered and any detected contaminants. It summarizes monitoring results and required health information.