Water Treatment Plant Operator key terms

The cloudiness of water caused by suspended particles that scatter light. It is measured in nephelometric turbidity units and is a key indicator of treatment effectiveness and microbial risk.

The total amount of carbon bound in organic compounds in water. Operators monitor it because organics consume disinfectant and form disinfection byproducts when chlorinated.

The water's capacity to neutralize acid, mainly from bicarbonate, carbonate, and hydroxide. It buffers pH swings and influences how much coagulant is needed and how well it works.

The concentration of dissolved calcium and magnesium in water, usually reported as calcium carbonate equivalent. It affects scaling, soap consumption, and some treatment chemical reactions.

The rapid mixing of a chemical such as alum or ferric chloride into water to neutralize particle charges so tiny suspended solids can clump together into larger particles.

Gentle, slow stirring of chemically treated water that encourages small destabilized particles to collide and grow into larger, settleable clumps called floc.

A bench-scale procedure that simulates coagulation, flocculation, and settling at several chemical doses so operators can select the best coagulant dose and pH.

The chemical dose that produces the best settled water quality at the lowest practical cost and chemical use, determined through jar testing and confirmed by plant performance data.

A gravity process in which water sits or flows slowly through a basin so heavier particles and floc settle to the bottom as sludge before the water moves on to filtration.

The flow through a settling basin divided by its surface area, expressed as flow per unit area per day. It is a design and operating measure of how well a clarifier can remove particles.

The granular material, commonly sand and anthracite, through which water passes to remove remaining particles. Media type, size, and depth determine filtration performance.

Reversing water flow upward through a filter at a high rate to lift and clean the media by washing out trapped solids. It is followed by a rinse before returning to service.

The period a filter operates between backwashes. Run length is limited by headloss buildup or by turbidity breakthrough, whichever occurs first.

The treated water leaving a filter. Its turbidity is monitored continuously and must stay below regulatory limits, including during filter-to-waste or restart conditions.

The loss of pressure or water level as water flows through a filter or pipe due to friction and accumulated solids. Rising headloss signals that a filter needs backwashing.

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

The product of disinfectant residual concentration and contact time used to demonstrate pathogen inactivation. Required CT depends on disinfectant type, temperature, pH, and target organism.

The concentration of chlorine remaining in water after demand is satisfied. Free residual protects against contamination, while total residual includes combined forms such as chloramines.

The amount of chlorine consumed by impurities in water before a persistent residual can be maintained. It is the difference between the dose applied and the residual measured.

The process of measuring actual chemical output against pump settings so the dose delivered matches the intended dose. It is checked with a drawdown test or graduated cylinder.

The quantity of chemical delivered per unit time or per volume of water treated, usually expressed in milligrams per liter or pounds per day. It is set from dose and flow.

A curbed, coated, or diked area or vessel that holds spills or leaks from chemical storage tanks so they cannot reach floors, drains, or the environment.

A graph showing the relationship between flow rate and head for a given pump. It is used with the system curve to find the operating point.

The absolute pressure margin at a pump suction that keeps liquid from vaporizing and causing cavitation. Required NPSH must be available at all operating flows.

The formation and collapse of vapor bubbles in a pump when suction pressure is too low. It causes noise, vibration, and damage to the impeller and casing.

The total pressure a pump must overcome at a given flow, combining static lift, friction losses, and discharge pressure. It is plotted against the pump curve to find the operating point.

A calculated number indicating whether water tends to deposit calcium carbonate scale or dissolve protective pipe coatings. Positive values suggest scaling, negative values suggest corrosion.

A logarithmic measure of hydrogen ion concentration indicating how acidic or basic water is on a scale from 0 to 14. It strongly affects coagulation, disinfection, and corrosion control.

A supervisory control and data acquisition system that collects sensor data and lets operators monitor and control plant processes remotely, often with alarms and trend logging.

An industrial computer that runs automated control logic for equipment such as valves, pumps, and chemical feeders based on sensor inputs and programmed setpoints.

The target value a control system maintains for a process variable, such as a chlorine residual or water level. Controllers adjust equipment to keep the variable near this value.

Any actual or potential link between a drinking water supply and a source of contamination that could allow backflow into the distribution system.

A testable device such as a reduced pressure zone assembly or double check valve that stops contaminated water from flowing backward into the potable supply.

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

The highest level of a regulated contaminant allowed in drinking water delivered to consumers. It is an enforceable standard based on health effects and feasibility.

The required process of informing customers when a water system violates a drinking water standard or has a situation posing a health risk, with timing and content set by regulation.

An annual report each community water system must deliver to customers describing source water, detected contaminants, compliance status, and health information.

A space with limited entry or exit that is not designed for continuous occupancy, such as a wet well or vault. Entry requires testing, ventilation, and an attendant.

A procedure that isolates hazardous energy sources with locks and tags before maintenance so equipment cannot start unexpectedly and injure workers.