MO 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 coagulated water that encourages small clumps to collide and grow into larger, settleable floc particles without breaking them apart.

A quiet settling basin where water moves slowly enough that suspended floc and solids sink to the bottom and are drawn off as sludge.

Passing water through a bed of sand, anthracite, or other media to trap remaining particles and organisms that did not settle out earlier in treatment.

Reversing or scouring flow upward through a filter bed to lift and carry away trapped solids, restoring the filter's ability to pass water and remove particles.

A measure of how cloudy water is because of suspended particles; high readings can shield pathogens from disinfection and often signal treatment problems.

Killing or inactivating disease-causing organisms in water, usually with chlorine or another disinfectant, as the final barrier before water reaches customers.

The product of disinfectant residual concentration and contact time used to judge whether enough disinfection has been delivered to inactivate a target organism at a given temperature and pH.

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

Total organic carbon, a measure of the organic material in water that can feed bacteria, consume disinfectant, and form disinfection byproducts during treatment.

Water from rivers, lakes, reservoirs, or streams that is open to the environment and therefore requires filtration and disinfection under standard treatment rules.

Water drawn from wells or aquifers beneath the earth's surface, typically clearer and more protected than surface water but still subject to chemical and microbial contamination.

The amount of chlorine still present in treated water after the initial demand is satisfied; it protects the water against contamination as it travels through the distribution system.

A public health advisory telling customers to boil or otherwise disinfect tap water before drinking because the supply may be contaminated or treatment has been compromised.

Any actual or potential link between the drinking water supply and a source of nonpotable water or contamination that could be drawn back into the pipes.

Devices or practices such as air gaps and check valves that stop water from flowing backward into the drinking water system from a customer's plumbing or another source.

A physical separation between a drinking water outlet and the highest possible level of a contaminating source, providing the strongest form of backflow protection.

A large underground pipe that carries treated water from the source or storage facility through the distribution system to smaller service lines.

The smaller pipe that runs from the distribution main to a customer's building or meter, delivering water to an individual property.

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

An instrument that displays the pressure inside a pipe or system so operators can confirm the distribution system is delivering adequate pressure to customers.

A valved connection on a water main used by fire crews for firefighting and by utilities for flushing mains, testing flow, and releasing trapped air.

Deliberately running water through mains and out of hydrants or blowoffs to remove sediment, stale water, and biofilm and to refresh disinfectant residual.

The above-ground structure and immediate area around a well that must be protected from contamination to keep the groundwater supply safe.

Unwanted water entering a sanitary sewer system from stormwater connections, groundwater, or defective pipes, which adds flow that the treatment plant must handle.

A release of untreated sewage from the collection system, often caused by blockages or excess flow, that can contaminate surface water and create a public health hazard.

The first physical stage of wastewater treatment, where screens and settling tanks remove large debris and settleable solids before biological treatment begins.

The biological stage of wastewater treatment in which microorganisms consume dissolved and suspended organic matter, typically followed by settling to remove the organisms.

A biological treatment process in which a mixed community of microorganisms is kept suspended in aerated wastewater and consumes organic matter as it grows.

A tank where air or oxygen is added to wastewater to keep microorganisms alive and mixing them with the organic material they break down.

A bed of media over which wastewater is sprayed so that microorganisms growing on the media surface consume organic matter as the water trickles down.

The amount of oxygen dissolved in water; in aeration tanks it must stay high enough for the biological treatment organisms to stay healthy and active.

Biochemical oxygen demand, a measure of the oxygen microorganisms use to break down organic matter in a wastewater sample, used to judge treatment performance.

Total suspended solids, the concentration of solid particles carried in wastewater or effluent, a key measure of how well treatment has removed material.

A large settling tank in a wastewater plant where solids are allowed to sink to the bottom and be removed, producing a clearer overflow.

The solids removed from wastewater during settling and biological treatment, which must be thickened, digested, dewatered, and ultimately disposed of or reused.

A heated, sealed tank where bacteria break down sludge in the absence of oxygen, reducing its volume and producing biogas and a more stable product.

The network of pipes, manholes, lift stations, and pumps that gathers wastewater from homes and businesses and delivers it to the treatment plant.

A facility with pumps that raise wastewater to a higher elevation so it can continue flowing by gravity through the collection system 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.

An opening in a sewer line that gives crews access for inspection, cleaning, and repair and also provides ventilation for the collection system.

A space such as a manhole or wet well that is large enough to enter but has limited exit and may contain hazardous gases or low oxygen, requiring special safety procedures.

A toxic, foul-smelling gas produced by bacteria in sewage that can collect in sewers and manholes, creating both a health hazard and corrosion problems.

The first step in wastewater treatment, where bar screens or grates catch rags, plastics, and large debris to protect downstream pumps and equipment.

A collection step that settles out heavy material such as sand and gravel so it does not wear out pumps or clog downstream treatment processes.