IL Water/WW Operator key terms

Water taken from a river, lake, reservoir, or well before any treatment is applied. Its quality determines which treatment processes a plant must use.

Water from rivers, streams, lakes, or reservoirs that is exposed to the atmosphere and to runoff. In Illinois it generally requires filtration and disinfection.

Water drawn from wells or springs below the ground surface. It is often lower in particles than surface water but may contain minerals, hardness, or contaminants.

An underground layer of sand, gravel, or rock that holds and transmits water in usable amounts. Wells are drilled into aquifers to supply drinking water.

The land area that drains into a particular river, lake, or reservoir. Protecting the watershed reduces the contamination that treatment must remove.

Cloudiness in water caused by suspended particles such as silt, clay, or organic matter. It is measured in NTU and can shield pathogens from disinfection.

Adding a chemical such as alum to raw water and mixing it rapidly so tiny particles clump together. This makes them removable by settling and filtration.

Gentle, slow stirring that encourages small coagulated particles to collide and form larger clumps called floc, which can then settle out.

A treatment step where water sits or moves slowly enough that floc and heavier particles settle to the bottom, producing clearer water. Also called clarification.

Passing water through a bed of sand, anthracite, or a membrane to remove remaining particles and many microorganisms. Surface water systems in Illinois must filter.

Using chlorine, chloramine, ozone, or ultraviolet light to kill or inactivate disease-causing organisms. It is the most important barrier against waterborne illness.

The concentration of chlorine remaining in water after treatment. It is measured to confirm disinfection and to protect water as it travels through pipes.

The product of disinfectant concentration and contact time, adjusted for temperature and pH. Operators use it to verify that disinfection is adequate.

Reversing the direction of flow through a filter to wash out trapped particles and restore the filter's ability to remove them.

A wastewater process in which air and a community of microorganisms break down organic matter in an aerated tank, producing a mixture that is later settled.

Adding air or oxygen to water or wastewater to support biological treatment, strip unwanted gases, or oxidize dissolved iron and other substances.

A settling tank that follows biological treatment. It separates treated water from the microorganisms and solids, some of which are returned to the process.

A pipe in the distribution system that carries treated water from the plant or storage to streets and service lines.

A pump placed in the distribution system to raise water pressure in a specific area or along a long or high-elevation line.

A tank that holds treated water to meet peak demand, supply fire flow, and maintain steady pressure in the distribution system.

Any actual or potential connection between drinking water piping and a source of contamination, such as a chemical line or irrigation system.

Devices or practices, such as air gaps and check valves, that stop contaminated water from flowing backward into the drinking water system.

A pressure surge caused by a sudden stop or change in water flow. It can crack pipes, damage fittings, and loosen joints.

A bench test that compares several coagulant doses and mixing speeds on raw water to find the best treatment settings.

Biochemical oxygen demand: the oxygen microorganisms consume while breaking down organic matter in a sample, usually over five days. High values indicate more pollution.

Total suspended solids: the mass of particles captured by filtering a water sample, reported in milligrams per liter. It measures how much solid material the water carries.

A scale from 0 to 14 that measures how acidic or basic water is. It affects chemical treatment, pipe corrosion, and disinfection effectiveness.

A single sample collected at one time and one location. It represents conditions at that moment rather than an average over time.

A sample made by combining portions collected at different times or locations. It gives an average picture of water quality over the sampling period.

A written record showing who collected, handled, and tested a sample and when. It helps prove that results are trustworthy and defensible.

A group of organisms used as indicators of contamination in drinking water. Their presence suggests treatment failure or that pathogens may be present.

The highest concentration of a contaminant allowed in drinking water under regulations, set to protect health.

A rule for a contaminant that can harm health. It is usually expressed as an MCL or as a required treatment technique.

A guideline for contaminants that mainly affect taste, odor, color, or appearance. These standards are not enforced for health reasons.

An annual report that community water systems must provide to customers, describing the water source, detected contaminants, and compliance with standards.

An on-site inspection of a water system's source, treatment, storage, and distribution to identify conditions that could contaminate drinking water.

A space with limited entry and exit that is not meant for continuous occupancy and may hold dangerous air, such as a vault or tank.

A safety practice that isolates and locks energy sources before equipment is serviced, preventing accidental startup or release of stored energy.

Personal protective equipment such as gloves, safety glasses, and respirators. It reduces a worker's exposure to chemicals, pathogens, and physical hazards.

Chemicals such as trihalomethanes that form when disinfectants react with organic material in water. They are regulated because long-term exposure may harm health.