AZ Water Operator key terms

An underground layer of rock, sand, or gravel that holds and transmits water in usable quantities. Wells and springs draw from aquifers, which are recharged slowly and can be depleted or contaminated.

The land area that drains rainfall and runoff to a common point such as a river, lake, or intake. Activities within a watershed directly affect raw water quality at the treatment plant.

Planned actions to prevent contamination of lakes, rivers, springs, and aquifers used for drinking water. Measures include land-use controls, wellhead buffers, spill response planning, and public education.

The cone-shaped lowering of the water table around a pumping well. It forms because water is removed faster than it flows in, and it can pull nearby contaminants toward the well.

Rapid mixing of a chemical such as alum into water to neutralize the electrical charges on suspended particles. Destabilized particles can then stick together instead of repelling each other.

Gentle, slow stirring that encourages destabilized particles to collide and clump into larger, settleable masses called floc. Mixing energy and time are controlled so floc grows without being broken apart.

Clusters of particles bound together after coagulation and flocculation. Good floc is visible, settles readily in the basin, and is removed by sedimentation and filtration.

A quiet settling basin where water moves slowly enough for suspended solids and floc to sink to the bottom as sludge. Removal efficiency depends on detention time, flow rate, and particle density.

Passing water through a bed of sand, anthracite, or other media to trap remaining particles, including pathogens. Filters are the final particle barrier before disinfection and require periodic backwashing.

Reversing flow upward through a filter at high rate to lift and clean the media and flush trapped solids to waste. Backwash is triggered by headloss, turbidity breakthrough, or a set time interval.

Cloudiness caused by suspended particles that scatter light in water. Measured in nephelometric turbidity units, it is a key indicator of filtration performance and microbial risk.

The unit reported by a turbidimeter, which measures light scattered at a defined angle by particles in a sample. Regulatory limits and reporting are expressed in these units.

The product of disinfectant residual concentration and contact time used to judge disinfection strength against pathogens. Higher concentration or longer contact time gives a larger, more protective value.

The amount of chlorine still present in treated water after demand is satisfied. Free residual protects against contamination in the distribution system and is monitored routinely.

Compounds such as trihalomethanes and haloacetic acids that form when disinfectants react with natural organic matter. Their formation is limited by removing organics before disinfection.

A bench-scale test using multiple stirred jars to compare coagulant doses and determine the best chemical feed settings. It simulates plant mixing, flocculation, and settling on a small scale.

A positive-displacement metering pump that injects a precise, adjustable volume of treatment chemical into water. Feed rate is verified by drawdown tests and calibration against actual plant flow.

Checking and adjusting a meter or feed device against a known standard or measured volume. Calibration ensures chemical doses, flow readings, and analyzers report accurate values.

A liquid chlorine compound commonly used for disinfection and residual maintenance. It degrades over time and with heat or sunlight, so strength must be checked and storage conditions controlled.

Any actual or potential link between the drinking water system and a source of nonpotable fluid. Without protection, backflow can draw contaminants into the distribution piping.

An assembly or device that stops reverse flow of water into the potable system. Common types include reduced-pressure zone assemblies and double check valves, tested on a set schedule.

A physical separation between a water supply outlet and the flood level of a receiving vessel. It is the most reliable backflow protection because no mechanical parts can fail.

A pipe branch that terminates with no outlet or loop, allowing water to stagnate. Stagnant dead ends lose disinfectant residual and can support biofilm growth.

Controlled release of water through hydrants or blowoffs to remove sediment, stale water, and biofilm. Flushing restores chlorine residual and is often done after main repairs.

The loss of pressure energy as water moves through pipes, valves, or filter media due to friction. Rising filter headloss signals a need to backwash.

A pump that spins an impeller to throw water outward and convert velocity into pressure. It is common for moving large flows and requires priming when the suction source is below the pump.

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

The margin of absolute pressure above a liquid's vapor pressure at the pump suction. Adequate margin prevents cavitation and is a key pump selection and installation check.

A valve that automatically lowers downstream pressure to a set value regardless of upstream changes. It protects piping and customer plumbing from excessive pressure in the distribution system.

A pressure surge caused by rapid changes in flow, such as a fast valve closure or pump trip. It can break pipes and damage fittings and is controlled with slow-closing valves and surge protection.

A reservoir holding treated water to meet peak demand, provide fire flow, and maintain system pressure. Tanks must keep water fresh and protect quality through mixing, turnover, and sealed openings.

Combining samples collected at different times or locations into one container for laboratory analysis. It gives an average result and is not suitable when peak or worst-case values matter.

A single sample taken at one place and time and analyzed on its own. It captures the conditions at that moment and is required when maximum or minimum values are regulated.

A documented record of who collected, handled, and stored a sample and when. It preserves legal defensibility by showing the sample was not altered or mishandled.

The highest concentration of a regulated contaminant allowed in delivered drinking water. It is an enforceable standard set to protect public health over a lifetime of exposure.

The non-enforceable health-based level of a contaminant below which no known or expected health risk exists. It is a target that treatment aims for, while the enforceable level may be higher.

Required communication to customers when a water system violates a standard or faces a health risk. Notices must be delivered within set timeframes and describe the problem, health effects, and corrective actions.

A space large enough to enter, with limited entry or exit, not designed for continuous occupancy. Entry requires a permit, atmospheric testing, ventilation, and an attendant outside.

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