Water Treatment Operator Class III key terms

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 microbial risk.

The concentration of organic matter in water, expressed as milligrams of carbon per liter. It matters because organics react with disinfectants to form disinfection byproducts.

The water's capacity to neutralize acid, mainly from bicarbonate, carbonate, and hydroxide. It buffers pH and strongly affects how well coagulants work.

A logarithmic scale from 0 to 14 describing hydrogen ion concentration. It governs coagulant solubility, disinfection effectiveness, corrosion control, and treatment stability.

The rapid mixing of a chemical coagulant into water to destabilize particle charges so small particles can stick together. It is the first major particle-removal step.

A chemical such as aluminum sulfate, ferric chloride, or a polymer added to water to neutralize particle surface charges and promote aggregation. Dosage must be matched to raw water quality.

A bench-scale procedure that mixes several coagulant doses with raw water under controlled rapid and slow mixing. It predicts full-scale coagulant dose and mixing conditions.

A measure of the electrical charge at the boundary between a particle and surrounding water. It indicates whether particles repel each other or are destabilized enough to aggregate.

Gentle, prolonged mixing that encourages destabilized particles to collide and grow into larger, settleable floc. It follows coagulation and precedes sedimentation.

Clumps of particles and coagulant held together by chemical and physical bonds. Good floc is large, dense, and resistant to shearing so it settles readily.

The gravity settling of suspended floc and particles in a basin with low flow velocity. Also called clarification, it removes most solids before filtration.

The flow rate through a settling basin divided by its surface area, expressed as gallons per day per square foot. It is a main design and performance measure for clarifiers.

A suspended layer of accumulated solids in a clarifier or solids-contact unit through which incoming water passes. It traps particles and must be controlled to avoid carryover.

The average time water stays in a basin, tank, or pipe, calculated as volume divided by flow rate. It affects settling, disinfection, and chemical reaction completion.

The granular material such as sand, anthracite, or garnet through which water passes to remove remaining particles. Grading and depth determine removal efficiency and run length.

A reverse flow of water, often with air scour, through a filter to dislodge and flush out trapped solids. Proper backwash restores media condition and prevents mudballs.

The pressure or energy lost as water moves through pipes, valves, or filter media. Rising filter head loss signals solids accumulation and approaching backwash need.

The treated water leaving a filter. Its turbidity is monitored continuously and is a primary measure of filtration effectiveness and pathogen barrier integrity.

The period after backwash when a filter's particle removal improves from poor to optimal as media pores and surface deposits redevelop. Effluent is often diverted during this time.

The product of disinfectant residual concentration and contact time used to estimate pathogen inactivation. Required CT varies with disinfectant, temperature, pH, and target organism.

The concentration of active disinfectant remaining in treated water at a given point. It provides a barrier against microbial regrowth in the distribution system and is regulated.

Chemicals such as trihalomethanes and haloacetic acids formed when disinfectants react with natural organic matter. Their concentrations are limited by regulation.

A regulated group of four byproducts (chloroform, bromoform, bromodichloromethane, dibromochloromethane) formed mainly by chlorine reacting with organics. Compliance is based on distribution system samples.

A positive-displacement metering pump that injects a precise chemical dose into water. Its calibration and stroke settings directly control treatment chemical application rates.

The process of verifying and adjusting an instrument or feed device so its output matches a known standard. Regular calibration ensures accurate dosing and reliable monitoring data.

An instrument that measures turbidity by detecting light scattered by suspended particles. It requires routine calibration with formazin or other approved standards for valid results.

A single sample collected at one point in time and place, not composited. It represents conditions only at the moment of collection.

A documented, unbroken record of who collected, handled, and stored a sample from collection through analysis. It protects the legal defensibility of monitoring results.

A pump that uses a spinning impeller to add velocity and pressure to water. Its performance is described by a pump curve relating flow and head.

A graph showing the relationship between a pump's flow rate and the head it develops. It is used with a system curve to find the operating point.

The absolute pressure margin at a pump's suction above the liquid's vapor pressure, preventing cavitation. Inadequate NPSH causes noise, vibration, and impeller damage.

The formation and collapse of vapor bubbles in a pump when local pressure drops too low. It causes noise, vibration, reduced flow, and progressive damage to impellers.

A pressure surge caused by rapid changes in flow velocity, such as sudden valve closure. It can damage pipes and fittings and is controlled with slow-closing valves and surge protection.

A valve that automatically lowers and holds downstream pressure to a set value. It protects distribution piping and customer plumbing from excessive pressure.

The highest legally permitted concentration of a contaminant in delivered water. It is an enforceable primary drinking water standard based on health effects.

A required treatment process or practice, used instead of a numeric limit when contaminant measurement is impractical. Failure to meet it is a violation.

The required communication to water customers when a violation or risk occurs. It specifies tiered deadlines and content based on the severity of the situation.

A permit-controlled procedure for entering spaces with limited access and hazardous atmosphere. It requires atmospheric testing, ventilation, attendants, and rescue provisions.

A procedure that isolates hazardous energy sources with locks and tags before maintenance. It protects workers from unexpected startup or release of stored energy.

Any actual or potential link between a potable water system and a source of contamination. Backflow prevention devices and programs are used to eliminate them.

Devices and practices such as air gaps and reduced-pressure zone assemblies that stop contaminated water from reversing into the drinking water system.