ABC Class II Water Treatment key terms

Cloudiness in water caused by suspended particles that scatter light. Measured in NTU, it indicates how well filtration and disinfection are working and whether pathogens may be shielded.

The land area that drains runoff into a lake, river, or reservoir used as a drinking water source. Protecting it reduces the contaminants that reach the intake.

An on-site review of a water system's source, treatment, storage, and operations to find health risks and compliance problems. Regulations require these surveys at set intervals.

A measurement of the organic material dissolved or suspended in water. High TOC increases coagulant demand, feeds bacteria, and forms disinfection byproducts when chlorine is applied.

The water's ability to neutralize acid, mostly from bicarbonate and carbonate. It buffers pH changes during coagulation and affects how much coagulant and disinfectant chemistry will work effectively.

A protozoan parasite that forms tough cysts and causes gastrointestinal illness. Its resistance to chlorine is the reason filters and adequate disinfection are both required.

A groundwater source that shows significant and rapid contamination from nearby surface water, judged by geology, flow, or water quality indicators. It must receive full surface-water treatment.

A chemical such as alum or ferric chloride that is added to water to reduce the electrical charge on particles so they can clump together and settle.

A brief, intense mixing step that spreads coagulant evenly through the water so the chemical reaction with particles starts quickly, before flocculation begins.

The electrical charge measured at the surface of a particle. Most colloids repel each other, and coagulants work by neutralizing this charge so particles can stick together.

Slow, gentle stirring that makes destabilized particles collide and stick together, building larger clusters that are heavy enough to settle or be filtered out.

Clusters of particles held together by coagulant chemicals. Well-formed floc settles quickly in a clarifier and is easier for filters to capture.

A bench test with beakers, mixers, and chemicals that lets an operator compare coagulant doses and pH values to choose the best full-scale treatment settings.

A tank where flow slows so that floc settles to the bottom as sludge while clarified water rises and leaves over a weir at the top.

The basin's flow rate divided by its surface area, expressed in gallons per minute per square foot. It shows whether particles have enough time to settle out.

A suspended layer of previously settled floc in a clarifier. As water rises through it, incoming particles are trapped and removed, improving clarification.

Layers of granular material such as sand, anthracite, and garnet that water passes through. Particles are trapped in the pore spaces, mostly near the top surface.

Reversing flow upward through a filter at a high rate to expand the media and wash out trapped particles. It restores the filter's ability to remove particles.

The pressure drop as water moves through a filter, measured in feet or psi. Rising head loss shows the filter is clogging and needs cleaning.

The point when particles pass through a filter and appear in the finished water. It is often signaled by rising effluent turbidity before the filter reaches terminal head loss.

Sending filtered water to drain for a short time after backwashing until turbidity is low again, which prevents a particle spike from entering finished water.

The product of disinfectant concentration in mg/L and effective contact time in minutes. Operators use CT values to show that enough pathogen inactivation has been achieved.

The amount of chlorine used up by organisms, ammonia, iron, manganese, and other impurities in the water before any measurable free residual remains.

The chlorine left as hypochlorous acid and hypochlorite ion after demand is satisfied. It is the active form that inactivates pathogens and protects water in the distribution system.

Compounds such as trihalomethanes and haloacetic acids that form when chlorine reacts with natural organic matter; they are regulated because of long-term health risks.

A liquid chlorine solution used for disinfection. It loses strength with heat, sunlight, and time, so it must be stored cool, out of sunlight, and used promptly.

A positive displacement pump that delivers a precise, adjustable volume of chemical per stroke, used to feed coagulants, fluoride, and disinfectants at controlled rates.

A curbed, diked, or double-walled area around a chemical tank or drum that captures leaks and spills so they cannot reach soil, drains, or water supplies.

A pump with a spinning impeller that throws water outward to create flow. It is suited to high volumes at moderate pressure but must not run dry.

Vapor bubbles forming and collapsing in a pump because suction pressure is too low. It causes noise, vibration, reduced flow, and pitting damage to the impeller.

Checking an instrument's reading against a known standard and adjusting it until accurate. Turbidimeters, pH meters, and chemical feed pumps all need routine calibration.

A single sample taken at one place and time. It represents conditions at that moment and is used for chlorine residual, pH, temperature, and turbidity.

A written record of everyone who collected, handled, and transferred a sample. It proves sample integrity and makes the laboratory results defensible.

Influent concentration minus effluent concentration, divided by influent concentration, times 100. It shows how well a unit process is performing.

The highest concentration of a regulated contaminant allowed in drinking water under the Safe Drinking Water Act. It is enforceable and set to protect public health.

An annual report community water systems must give customers, listing source water, detected contaminants, and compliance status, so the public understands what is in their water.

An area with limited entry and exit, poor ventilation, and no continuous occupancy, such as a wet well or vault. Entry requires a permit, air testing, and a standby attendant.

A procedure that isolates hazardous energy by locking switches and closing and locking valves, then tagging them, to protect workers during maintenance or repair.

A standardized document describing a chemical's hazards, safe handling, first aid, and spill response, kept where employees can reach it.