OH Water/Wastewater Operator key terms

The rapid mixing of a chemical such as alum into raw water so that tiny suspended particles clump together into larger, heavier masses that can be removed in later treatment steps.

Gentle, slow stirring of chemically treated water that encourages small clumped particles to collide and grow into larger, settleable floc without breaking the fragile masses apart.

A quiet settling period in a basin where gravity pulls floc and other suspended solids to the bottom, producing clearer water that flows on to filtration.

A measure of how cloudy water appears because suspended particles scatter light; it is reported in nephelometric turbidity units and is a key indicator of treatment performance and microbial risk.

Reversing or scouring flow through a filter bed to wash trapped particles out to waste, restoring the media's ability to remove solids from treated water.

The granular material, commonly sand, anthracite, or mixed layers, that a filter bed is built from and that physically strains and attaches particles as water passes through.

The product of disinfectant residual concentration and contact time used to judge how effectively pathogens are inactivated; required CT varies with disinfectant, temperature, pH, and target organism.

Chemicals such as trihalomethanes and haloacetic acids that form when disinfectants react with natural organic matter, and which are regulated because of long-term health concerns.

A legally enforceable maximum contaminant level or treatment technique set to protect public health from contaminants that pose acute or chronic risks in drinking water.

The highest concentration of a regulated contaminant allowed in water delivered to consumers, set as close to a health-based goal as treatment technology and cost reasonably permit.

A non-enforceable guideline addressing aesthetic concerns such as taste, odor, color, corrosivity, or staining rather than direct health effects, though states may choose to enforce it.

A groundwater source close enough to surface water, or connected through preferential pathways, that it may carry surface-water pathogens and therefore requires enhanced treatment and monitoring.

A study identifying the land areas and activities that can contaminate a public water system's source, rating the source's susceptibility and guiding protection efforts.

A large buried pipe that carries treated water from pumps or storage through streets to serve many customers and fire hydrants in a distribution system.

The pipe that carries water from the public water main to a single building or customer meter, marking the boundary between utility and private responsibility.

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

A testable device such as a reduced-pressure-zone assembly or double check valve installed to stop reverse flow of contaminated water into a potable supply.

A physical, unobstructed vertical separation between a potable water outlet and the flood-level rim of a receiving vessel, the most reliable form of backflow protection.

Tanks, reservoirs, or standpipes that hold treated water to meet peak demand, provide fire flow, stabilize pressure, and maintain disinfectant residual across the system.

The length of time water spends traveling from treatment through the distribution system to a customer; older water loses disinfectant residual and can develop taste, odor, or bacterial problems.

The measurable amount of disinfectant remaining in treated water as it moves through pipes, which protects against contamination introduced after the treatment plant.

A line representing the pressure head of water at points along a pipe or system, used to analyze pressure, flow direction, and where a system may draw air or leak.

A portion of a distribution system served at a controlled pressure range, often by a booster pump or pressure-reducing valve, to keep pressures adequate but not excessive.

A pump placed within the distribution system to raise pressure or move water into higher elevations or distant areas where the main supply cannot maintain adequate pressure.

A pressure surge caused by a sudden change in flow velocity, such as fast valve closure, that travels through piping and can damage pipes and fittings.

Stormwater, groundwater, and other clear water that enters a sanitary sewer through illegal connections, cracked pipes, joints, and manholes, adding flow the treatment plant must handle.

A release of untreated sewage from a sanitary sewer system before it reaches the treatment plant, often caused by blockages, root intrusion, or excessive inflow and infiltration.

A discharge of mixed stormwater and raw sewage from a system that carries both, occurring when heavy rain exceeds capacity and the mixture is released to a waterway.

The first wastewater treatment stage, using screens and grit removal to take out large debris and heavy inorganic solids that could damage or clog downstream equipment.

A settling tank where wastewater slows enough for heavier solids to settle as sludge and lighter material to rise as scum, removing a large share of suspended solids.

A secondary treatment process in which air and recycled microorganism-rich sludge are mixed with wastewater so bacteria consume dissolved organic matter and form settleable solids.

The biological stage of wastewater treatment in which microorganisms break down dissolved and colloidal organic material, typically followed by settling to remove the resulting solids.

The concentration of microorganisms and solids suspended in the aerated mixture of an activated sludge basin, a key measure for controlling the food-to-microorganism ratio and sludge age.

Settled biological sludge collected from the secondary clarifier and pumped back to the aeration basin to keep enough active microorganisms working on incoming wastewater.

The average time solids remain in the biological treatment system, controlled by wasting sludge; it influences which organisms thrive and how well the process settles.

Excess biological solids deliberately removed from the treatment process to control sludge age and maintain the desired balance of microorganisms in the aeration system.

A facility with pumps and a wet well that raises wastewater to a higher elevation so it can continue by gravity to the treatment plant.

A pipe that carries wastewater under pressure from a pump or lift station to a point where gravity flow can resume.

A collection pipe laid on a continuous downward slope so wastewater flows by gravity alone, requiring no pumping but needing adequate grade and depth.

An opening in the collection system that provides access for inspection, cleaning, and repair, and where adjacent sewer sections join or change direction, grade, or size.