NE Water/Wastewater Operator key terms

Adding a chemical such as alum to water so tiny suspended particles lose their electrical repulsion and begin to stick together. This early clumping makes later settling and filtering far more effective.

Gentle, slow stirring of chemically treated water that lets small particle clumps bump into each other and grow into larger, heavier masses called flocs, which can then be removed by settling or filtration.

A quiet basin where water moves slowly enough that heavier particles and flocs settle to the bottom under gravity. The settled material, called sludge, is removed and clearer water flows on to filtration.

Passing water through a bed of sand, anthracite, or other media that traps remaining particles and some microorganisms. It is the final particle-removal step before disinfection in a conventional plant.

Treating water with chlorine, ozone, ultraviolet light, or another agent to inactivate or kill disease-causing organisms. It is the most important barrier against waterborne illness at a treatment plant.

The product of disinfectant concentration in mg/L and contact time in minutes. Operators use CT to judge whether enough germ-killing exposure occurred at the measured temperature and pH.

A measure of how cloudy water appears because of suspended particles, reported in nephelometric turbidity units. High turbidity can shield microorganisms from disinfection and signals treatment problems.

A bench-scale test in which several beakers of raw water receive different coagulant doses and are stirred at controlled speeds. The operator compares results to choose the most effective and economical dose.

Reversing normal flow through a filter, often with air scour, to wash trapped particles out of the media. Backwashing restores particle removal and is scheduled by head loss or effluent turbidity.

A large buried pipe that carries treated water through streets to serve many properties. Mains are typically sized for fire flow and are valued so sections can be isolated for repair.

A valved connection on a water main that lets firefighters draw large flows and that crews use for flushing and pressure testing. Hydrants must be inspected and exercised to stay operational.

A valve that lowers a higher upstream pressure to a steadier, lower downstream pressure. These valves protect piping and appliances and help define separate pressure zones in hilly service areas.

Any actual or potential link between the drinking water system and a source of contamination, such as a hose submerged in a chemical tank. Preventing them is a core distribution safety duty.

A device that stops water from flowing backward into the drinking water supply. Common types include reduced-pressure-zone assemblies and double check valves, which must be tested on a regular schedule.

A pressure surge caused by suddenly stopping or changing the flow of water, as when a valve closes too fast. It can crack pipes and damage fittings, so valves are closed slowly.

A concrete or restrained fitting placed at bends, tees, and valves to resist the push of water pressure that tries to separate pipe joints. Without it, joints can blow apart.

A tank on a tall structure that uses gravity to hold pressure in the distribution system and supply water during high demand or power outages. Its level rises and falls with system demand.

The raw wastewater entering a treatment plant, carrying solids, organic matter, and microorganisms from homes and businesses. Its flow and strength vary through the day and must be measured.

The treated water that leaves a wastewater plant and is discharged to a receiving stream or reused. It must meet permit limits for parameters such as BOD and suspended solids.

The first treatment stage, where bar screens remove rags and large debris and grit chambers settle sand and heavy solids. The goal is protecting downstream pumps and processes from damage and wear.

A settling tank that removes settleable solids and floating grease before biological treatment. It reduces the organic load on downstream processes and produces primary sludge for handling.

A biological process where a mixed community of bacteria and other organisms consumes organic matter in aerated wastewater. The organisms are settled out and returned to keep the population working.

The settled biomass from the secondary clarifier that is pumped back to the aeration basin so enough microorganisms remain to treat incoming waste. The return rate is adjusted to control solids inventory.

The concentration of microorganisms and other solids in the aeration tank. Operators measure it to calculate the food-to-microorganism ratio and the solids retention time.

The pounds of organic food entering per day divided by the pounds of microorganisms in the aeration system. It guides how much sludge to waste and how well the process performs.

Biochemical oxygen demand estimates the oxygen microorganisms use while breaking down organic matter in a sample, usually over five days. It is a key measure of wastewater strength and plant performance.

Also called sludge age, this is the average time microorganisms stay in the treatment system. Longer retention favors nitrification and reduces sludge production but requires more aeration.

A two-step biological process in which bacteria convert ammonia to nitrite and then to nitrate. It consumes oxygen and alkalinity and matters greatly where ammonia limits apply.

A heated, oxygen-free tank process in which bacteria break down sludge, producing methane and reducing pathogens and volatile solids. The stabilized biosolids can then be dewatered and beneficially used.

A pipe system that carries only domestic and commercial wastewater, not stormwater, to a treatment plant. Keeping stormwater out is essential to prevent overloads and overflows.

A separate pipe system that carries rain and snowmelt directly to a receiving water without treatment. Storm sewers are not designed to accept sanitary waste.

A single pipe that carries both sanitary wastewater and stormwater. During heavy rain these systems can overflow an untreated mixture to streams, so they are managed with storage or separation projects.

Groundwater that seeps into sewer pipes through cracks, joints, and defective manholes. It adds clear water to the flow and can overload the system during wet weather.

Stormwater or other clear water that enters a sewer directly through illegal connections, roof drains, or manhole covers. Unlike infiltration, it arrives quickly during rain events.

An access opening in a sewer line that lets crews inspect, clean, and repair the pipe. Manholes are placed at changes in direction, grade, or pipe size.

A facility with pumps that raise wastewater to a higher elevation so it can continue flowing by gravity. It includes a wet well, pumps, controls, and often emergency storage or power.

A pipe that carries wastewater under pressure from a pump station to a point where gravity flow can resume. Air release valves and corrosion control are common maintenance concerns.

A condition where flow fills a sewer above its normal capacity, putting pressure on covers and joints. Surcharging can lead to backups into basements and uncontrolled overflows.

The release of untreated or partially treated wastewater from the collection system before it reaches the plant. Overflows threaten public health and receiving waters and must be reported.

A closed-circuit television camera pulled through a sewer to record its condition and find cracks, roots, and blockages. The footage guides cleaning, repair, and rehabilitation decisions.