OK Water/Wastewater Operator key terms

The highest concentration of a contaminant legally allowed in drinking water supplied to the public. It is set by regulation and, for most contaminants, is based on health effects and is enforceable.

The non-enforceable health-based target for a contaminant in drinking water, set at a level with no known or expected adverse health effects with an adequate margin of safety. MCLs are set as close to MCLGs as feasible.

A required treatment method or performance standard that must be met when a contaminant cannot be reliably measured at low levels or when an MCL is impractical. Compliance is judged by process performance rather than a numeric concentration.

The cloudiness of water caused by suspended particles such as silt, clay, and organic matter. It is measured in nephelometric turbidity units (NTU) and is a key indicator of filtration performance and microbial risk.

Chemical compounds formed when disinfectants such as chlorine react with naturally occurring organic matter in water. Common examples include trihalomethanes and haloacetic acids, which are regulated in finished drinking water.

The concentration of chlorine remaining in water after treatment and travel through the distribution system. A detectable residual provides continuing protection against microbial contamination and is a routine compliance measurement.

Any actual or potential link between a potable water system and a source of nonpotable water or other substance. Without proper protection, backflow can draw contaminants into drinking water piping.

A testable mechanical device, such as a reduced-pressure-zone or double-check assembly, installed to stop reverse flow of water from a customer's plumbing or other source into the public water system.

An evaluation of the drinking water sources serving a public water system that identifies potential contamination threats and determines how susceptible each source is to those threats.

The surface and subsurface land area through which water and contaminants can move toward a public drinking water well. Land use within this area is often managed to reduce contamination risk.

An underground layer of rock, sand, or gravel that holds and transmits groundwater in usable quantities. Aquifers are the source for many public water supply wells.

The network of pipes, pumps, tanks, valves, and meters that delivers treated drinking water from the treatment plant to customers while maintaining adequate pressure and quality.

A public health advisory issued when drinking water may be contaminated by pathogens, instructing customers to boil water before drinking, cooking, or other uses. It is lifted after testing confirms safety.

A group of bacteria used as an indicator of drinking water quality and treatment effectiveness. Their presence in the distribution system can signal a problem with treatment or system integrity.

The wastewater or raw water entering a treatment process or plant. Its flow rate and pollutant concentrations determine the loading the treatment units must handle.

The treated water or wastewater leaving a treatment process, plant, or facility. Its quality is compared against permit limits before discharge to a receiving water.

A measure of the oxygen consumed by microorganisms as they break down organic matter in water over a set period, typically five days. It is a common indicator of organic pollution strength in wastewater.

The concentration of solid particles suspended in water that can be captured by a filter. TSS is a standard wastewater effluent limit and an indicator of treatment performance.

A biological wastewater treatment process in which a mixed community of microorganisms consumes organic matter in an aerated tank. Solids are then separated in a clarifier and partly returned to the process.

A settling tank that separates treated water from biological solids after aeration in a secondary treatment process. Clear overflow leaves as effluent while settled sludge is returned or wasted.

The solids removed from wastewater during treatment, including primary and secondary biological solids. Sludge must be thickened, digested, dewatered, or otherwise managed before disposal or beneficial reuse.

Treated sewage sludge that meets regulatory quality standards so it can be beneficially used, for example as a soil amendment or fertilizer. Biosolids are typically produced through digestion and dewatering.

A discharge of untreated sewage and stormwater from a combined sewer system when heavy rain exceeds the system's capacity. CSOs are a major source of pollution and are subject to control programs.

A release of untreated wastewater from a sanitary sewer system, often caused by blockages, infiltration, or inflow during wet weather. SSOs must be reported and corrected to protect public health.

Extraneous water entering a sanitary sewer system. Infiltration seeps in through defective pipes and joints, while inflow enters directly through connections such as roof drains and manhole covers.

Rainfall or snowmelt that runs off surfaces such as roofs, streets, and parking lots instead of soaking into the ground. It can carry pollutants into waterways and is often regulated through permits.

A structural or nonstructural measure used to reduce pollution or control runoff. Examples include detention basins, vegetated swales, and street sweeping programs.

A constructed depression that temporarily stores stormwater runoff and releases it slowly to reduce downstream flooding and erosion. Some designs also promote settling of pollutants.

A regulatory permit that authorizes and limits discharges of pollutants to surface waters. Wastewater treatment plants and many stormwater discharges operate under such permits.

A permit covering stormwater discharges from construction sites that disturb a threshold area of land. It typically requires an erosion and sediment control plan and regular inspections.

A site-specific document describing the practices and procedures a site will use to prevent stormwater from carrying pollutants off the property. It is often required for construction and industrial permits.

Practices such as silt fences, sediment basins, and mulching that keep soil in place and capture sediment before it leaves a construction site and reaches waterways.

A submission filed by an operator to indicate coverage under a general permit before starting a regulated activity. It typically includes site information and a certification of planned controls.

A filing submitted when a permitted activity is complete and permit coverage is no longer needed. It confirms that final stabilization or other closeout conditions have been met.

The land area that drains to a common waterbody, such as a river, lake, or estuary. Watershed boundaries are defined by topography, and activities within them affect downstream water quality.

A strategy document that identifies water quality problems and goals within a watershed and sets out actions, responsible parties, and schedules to address them.

The maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. It is allocated among point and nonpoint sources and guides reduction efforts.

Pollution that comes from diffuse sources across the landscape rather than a single pipe, such as runoff from farms, roads, and lawns. It is addressed through land management and watershed practices.

The process by which water moves downward from the land surface into an aquifer. Recharge rates affect long-term water supply availability and can be altered by development and impervious surfaces.