ID Water/WW 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 coagulated water that encourages small particle clumps to collide and grow into larger floc that settles or filters out efficiently.

A settling process in which water sits in a basin long enough for heavier solids and floc to sink to the bottom and be drawn off as sludge.

Passing water through beds of sand, anthracite, or other media to trap remaining particles, including many pathogens, before disinfection and distribution.

Reversing water flow upward through a filter bed to lift and flush out trapped solids, restoring the media's ability to filter water effectively.

The granular material, commonly sand, anthracite, or mixed layers, that forms the porous bed which removes particles as water passes through a filter.

A measure of how cloudy water is because suspended particles scatter light; high turbidity can shield pathogens from disinfection and signals treatment problems.

The unit reported by a turbidimeter, which measures light scattered at an angle by particles in a water sample; lower values indicate clearer water.

The chemical or physical treatment that inactivates disease-causing organisms in water, typically using chlorine, chloramine, ozone, chlorine dioxide, or ultraviolet light.

The product of disinfectant concentration and contact time used to judge how much pathogen inactivation a treatment step achieves at a given temperature and pH.

The amount of chlorine still present in water after treatment; a measurable residual protects against contamination as water travels through the distribution system.

Undesirable compounds such as trihalomethanes and haloacetic acids that form when disinfectants react with naturally occurring organic matter in water.

A measure of the carbon bound in natural organic compounds in water; it is a key precursor for disinfection byproducts and is reduced by coagulation and other processes.

Adjusting water chemistry, such as pH and alkalinity, or adding inhibitors so pipes and fixtures are not attacked and metals like lead and copper do not leach.

The water's capacity to neutralize acid, mainly from bicarbonate and carbonate; it buffers pH and helps determine whether water is stable or corrosive.

A logarithmic scale from 0 to 14 describing how acidic or basic water is, based on hydrogen ion activity; it affects treatment chemicals and pipe corrosion.

The network of mains, storage tanks, pumps, valves, and service lines that delivers finished drinking water from the treatment plant to customers at adequate pressure.

Any actual or potential link between a drinking water supply and a source of contamination, which requires a backflow prevention device or air gap.

Reverse flow of water in a piping system that can pull nonpotable water or chemicals into the drinking water supply when pressure drops.

A physical separation between a water outlet and the rim of a receiving vessel; it is the most reliable form of backflow protection.

A pump placed within the distribution network to raise or maintain pressure in an area where the main system pressure is not sufficient.

A pressure surge caused by a sudden change in flow, such as rapid valve closure, that sends a shock wave through piping and can damage it.

The downward movement of water through soil and porous media, used in wastewater treatment as a slow natural polishing step in the subsurface.

In collection systems, groundwater entering sewers through cracks and joints; in treatment, water soaking into soil. The exam context usually means unwanted clear water in pipes.

Stormwater or groundwater that enters a sanitary sewer through direct connections such as roof drains, sumps, or manhole covers rather than through defects.

A release of untreated sewage from a collection system before it reaches the treatment plant, often caused by blockages, infiltration, or storm inflows.

The first wastewater step, using screens and grit chambers to remove rags, debris, and heavy inorganic solids that would damage or clog downstream equipment.

A basin or channel that slows wastewater so dense, abrasive material like sand and coffee grounds settles out while lighter organic matter flows on.

Settling of raw wastewater in tanks to remove settleable solids and floating material, producing primary sludge and a clarified liquid for biological treatment.

Biological treatment in which microorganisms consume dissolved and suspended organic matter, usually followed by settling to separate the organisms from the treated water.

A biological process where a mixed community of microorganisms is aerated with wastewater, then separated in a clarifier and partly returned to seed incoming flow.

Settled microorganism-rich solids from the secondary clarifier that are pumped back to the aeration basin to keep the biological population high enough.

A settling tank after biological treatment where microorganism floc sinks and is separated from the clear treated water that flows over the weirs.

A condition where filamentous organisms make activated sludge settle poorly, so solids carry over the clarifier weirs and the effluent quality drops.

The ratio of organic food entering an aeration basin to the mass of microorganisms present; it is used to control sludge age and settling behavior.

The amount of dissolved oxygen microorganisms consume while breaking down organic matter in a sample over a set period, commonly five days.

Oxygen dissolved in water and available to aquatic life and to the microorganisms that treat wastewater; aeration basins must keep it at target levels.

Supplying air or oxygen to wastewater so aerobic microorganisms can break down organic matter; done with diffusers, blowers, or mechanical mixers.

The solids removed from wastewater during settling and treatment, which must be thickened, stabilized, and dewatered before reuse or disposal.