NH Water/Wastewater 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 filtration performance and microbial risk.

The unit used to report turbidity, based on how much light is scattered at a right angle by particles in a sample. Lower values indicate clearer water.

The process of adding chemicals such as alum or ferric chloride to neutralize particle charges so that small suspended solids can clump together and be removed in later treatment steps.

Gentle, slow mixing that encourages neutralized particles to collide and grow into larger, settleable clumps called floc after coagulant has been added.

A treatment step where water sits in a basin long enough for heavier floc and solids to settle to the bottom, producing clearer water that flows on to filtration.

Reversing or agitating flow through a filter to wash out trapped particles and restore the filter's ability to remove turbidity. Backwash water is usually recycled or discharged under permit.

Chemicals such as trihalomethanes and haloacetic acids that form when disinfectants like chlorine react with naturally occurring organic matter in water. They are regulated in finished drinking water.

A measure of the organic material in water that can react with disinfectants to form byproducts. Utilities monitor it to gauge source water quality and treatment effectiveness.

The amount of chlorine remaining in treated water after it has reacted with contaminants. A detectable residual protects water in the distribution system from recontamination.

A calculation combining disinfectant concentration (C) and contact time (T) used to demonstrate that a required level of pathogen inactivation has been achieved during disinfection.

A group of indicator organisms used to assess drinking water safety and treatment effectiveness. Their presence suggests possible contamination or a breakdown in treatment or distribution integrity.

A federal drinking water regulation setting monitoring and public notification requirements based on the presence of total coliforms and E. coli in distribution system samples.

A public health advisory telling customers to boil tap water before drinking or use bottled water because contamination is suspected or confirmed in the supply.

Any actual or potential link between a potable water system and a source of contamination, such as a submerged hose or industrial line, that could allow backflow into drinking water.

A mechanical assembly such as a reduced-pressure zone valve or air gap that stops contaminated water from flowing backward into a drinking water system.

A large buried pipe that carries treated water through the distribution system to smaller service lines and fire hydrants. Operators flush and repair mains to protect water quality.

Deliberately opening fire hydrants to move high flows through mains, scouring sediment and stale water from pipes and helping maintain chlorine residual in the distribution system.

A pressure surge caused by a sudden change in flow velocity, such as rapid valve closure, that can damage pipes and fittings and is often heard as a loud bang.

A test measuring the oxygen consumed by microorganisms breaking down organic matter in a wastewater sample over a set period, usually five days. It indicates organic strength and treatment performance.

The concentration of solid particles suspended in wastewater or effluent, determined by filtering and drying a sample. It is a common permit limit for treatment plant discharge.

A wastewater treatment process in which a mixed community of microorganisms consumes organic matter in an aerated basin, then is separated from the treated water in a clarifier.

A settling tank that follows aeration in activated sludge treatment, allowing biological solids to settle out so clear effluent can flow on while return sludge is sent back to the aeration basin.

Settled biological solids from the secondary clarifier that are pumped back into the aeration basin to maintain a healthy population of microorganisms for treating incoming wastewater.

The average time biological solids remain in an activated sludge system, calculated from the mass of solids in the aeration basin divided by the daily solids leaving the system. It guides wasting decisions.

Excess biological solids intentionally removed from an activated sludge system to control sludge age and prevent solids from building up beyond what the treatment process can handle.

Clean groundwater and stormwater that enter a sanitary sewer through cracks, joints, and improper connections, adding flow that treatment plants and collection systems must handle.

The release of untreated or partially treated wastewater from a sewer system before it reaches the treatment plant, often caused by blockages, inflow, or equipment failure, and reportable to regulators.

An early wastewater treatment step that uses settling or swirling to remove heavy material such as sand, gravel, and coffee grounds before it can damage pumps or clog downstream processes.

A settling tank near the start of wastewater treatment that removes settleable solids and floating scum before biological treatment, reducing the load on downstream processes.

A sample made by combining several portions collected over time or across a flow, giving a representative average concentration for permit monitoring rather than a single moment in time.

A single sample collected at one place and time. It is used when conditions change rapidly or when a composite would mask important short-term variation.

A documented record tracking who collected, handled, and transported a sample, and when, so results can be defended as legally valid in enforcement or compliance situations.

A periodic report submitted to regulators by permitted wastewater dischargers, listing measured effluent values and comparing them with permit limits.

The federal permitting program that controls point source discharges of pollutants to surface waters, setting effluent limits and monitoring requirements that treatment plants must meet.

An annual report that community water systems must deliver to customers, summarizing source water, detected contaminants, compliance status, and health information about the drinking water.

A space large enough to enter, with limited entry or exit, not designed for continuous occupancy. It requires testing and permitting before entry because of hazards like toxic gas or oxygen deficiency.

A toxic, flammable gas with a rotten-egg odor that forms in sewers and sludge. It deadens the sense of smell at higher concentrations and can be fatal in confined spaces.

A safety procedure in which energy sources are isolated, locked, and tagged before maintenance so equipment cannot be started unexpectedly and injure workers.