CA Water Operator key terms

The cloudiness of water caused by suspended particles that scatter light. Measured in nephelometric turbidity units (NTU), it indicates filtration performance and can shield pathogens from disinfection.

The land area that drains rainfall and snowmelt into a river, lake, or reservoir. Land uses and activities within a watershed shape the quality of the source water a treatment plant must handle.

Untreated water as it arrives at a treatment plant from a well, river, lake, or reservoir. Operators test raw water quality to decide which treatment processes and chemical doses are needed.

The water's capacity to neutralize acid, contributed mainly by bicarbonate, carbonate, and hydroxide. It buffers pH and affects how much coagulant is needed and how corrosive finished water may become.

A groundwater source influenced by nearby surface water, as shown by site conditions or water quality. It must be treated like surface water, typically requiring filtration and disinfection.

A group of organisms used as indicators of treatment effectiveness and distribution system integrity. Their presence suggests a breach or contamination, though most coliforms do not themselves cause illness.

A nitrogen compound common in agricultural groundwater and linked to blue baby syndrome. It has a primary drinking water standard and is monitored at the source before blending or treatment.

The rapid mixing of a chemical such as alum into water to neutralize particle charges so tiny suspended solids can stick together. It is the first step in conventional clarification.

Gentle, slow stirring that encourages small destabilized particles to collide and grow into larger, settleable masses. It follows coagulation and precedes sedimentation in a conventional plant.

The visible clump of particles formed when coagulated solids bind together. Well-formed floc settles quickly and is removed in clarifiers and filters rather than passing into finished water.

A tank where water moves slowly enough for floc and other solids to settle to the bottom as sludge. Also called a clarifier, it removes most solids before filtration.

A bench procedure that stirs several beakers of raw water with different coagulant doses and compares settling and turbidity. Operators use the results to set chemical feed rates.

Layers of granular material such as anthracite, sand, and garnet that water passes through to remove remaining particles. Media type, size, and depth determine filtration performance.

Reversing flow upward through a filter at a high rate to expand the media and wash out trapped solids. It restores capacity and is triggered by headloss, turbidity, or time set points.

The drop in pressure or water level caused by friction as water moves through filters, pipes, or fittings. Rising filter headloss signals that the filter needs backwashing.

The product of disinfectant concentration and contact time used to express disinfection strength against pathogens. Required CT depends on pH, temperature, and the target organism.

The concentration of uncombined chlorine remaining after demand is satisfied. It protects water in the distribution system and is measured routinely at plants and throughout the pipe network.

The amount of chlorine consumed by organic matter, metals, ammonia, and other reducing substances in water. The applied dose must exceed demand before any free residual remains.

A measure of natural and human-made organic material in water. Organics react with disinfectants to form byproducts, so many plants remove TOC through coagulation and filtration.

A group of regulated disinfection byproducts, including chloroform, formed when chlorine reacts with organic matter. Compliance is judged by running annual averages of samples from the distribution system.

A disinfectant made by combining chlorine with ammonia. It persists longer in pipes and forms fewer regulated byproducts, but it is a weaker primary disinfectant and needs careful process control.

Any actual or potential link between a potable water system and a source of contamination or pollution. Removing or protecting cross-connections prevents backflow from degrading drinking water.

Reverse flow of nonpotable water into a drinking water system, caused by backsiphonage or backpressure. It can contaminate the main and is prevented by air gaps and backflow prevention assemblies.

A physical separation between a potable water outlet and the flood rim of a receiving vessel. It is the most reliable backflow protection because it has no mechanical parts to fail.

A testable backflow preventer with two check valves and a relief valve, used where hazard is high. It guards against both backsiphonage and backpressure and requires periodic testing.

The average time water has spent in the distribution system since leaving the treatment plant. High water age lowers disinfectant residual and increases byproduct formation and stagnation problems.

How often the volume of water in a storage tank is replaced by new flow. Poor turnover leaves old, stagnant water that loses residual and may develop biofilm and sediment.

A graph showing the flow rate and head a pump can produce across its operating range. Operators compare it with the system curve to find the point where the pump actually runs.

The formation and collapse of vapor bubbles in a pump when local pressure falls too low, causing noise, vibration, and metal damage. Avoiding it requires adequate net positive suction head.

The absolute pressure available at a pump suction above the liquid's vapor pressure. Too little NPSH causes cavitation, reduced capacity, and damage to the impeller.

Equations predicting how changing pump speed or impeller diameter changes flow, head, and power. Flow varies with speed, head with the square of speed, and power with the cube.

A meter with no moving parts that measures flow from the voltage induced as conductive water passes through a magnetic field. It is accurate and widely used for plant and well flow measurement.

A valve that lowers incoming pressure to a set downstream value. It protects distribution piping and customer plumbing from excessive pressure that causes leaks and accelerated wear.

The highest concentration of a contaminant allowed in drinking water under the Safe Drinking Water Act. Primary MCLs are enforceable health-based limits set as close to goals as feasible.

A required treatment process rather than a contaminant concentration limit, used when measuring the contaminant is impractical. Filtration and corrosion control are common examples with enforceable requirements.

An annual report that community water systems must deliver to customers, describing source water, detected contaminants, and compliance status. It is a public right-to-know document.

Rules governing coliform monitoring and response in distribution systems. Repeat positive samples trigger a sanitary survey or assessment and corrective action instead of an automatic violation.

Requires sampling tap water at high-risk homes and applying corrosion control when action levels are exceeded. It targets pipe corrosion rather than treating lead directly.

A space large enough to enter, with limited entry and exit, that is not designed for continuous occupancy. Entry requires a permit, atmospheric testing, and an attendant to prevent asphyxiation or entrapment.

A periodic on-site review by the state of a water system's sources, facilities, and operations to find sanitary defects. Identified problems must be corrected within set timeframes.