AL Water Operator key terms

A measure of how cloudy water looks because of suspended particles such as silt, clay, or organic matter. It is reported in NTU and is used to judge source water quality and treatment performance.

A broad group of bacteria used as an indicator that a water system may be contaminated or that treatment has failed. Their presence requires repeat sampling and investigation.

A number from 0 to 14 describing whether water is acidic, neutral, or basic. It strongly affects coagulation, disinfection efficiency, and how corrosive the finished water becomes.

The ability of water to resist a drop in pH when acid is added, mostly from bicarbonate and carbonate. It helps stabilize treatment and protects against corrosive water.

The amount of dissolved calcium and magnesium in water, usually reported as milligrams per liter as calcium carbonate. Hard water forms scale in pipes and heaters but is not a primary health concern.

The land area that drains rainfall and runoff to a stream, lake, or reservoir used as a drinking water source. Activities in a watershed directly affect raw water quality.

Groundwater that is influenced by surface water, such as a spring or well near a river, so it must be treated with the same protective barriers as surface water.

Untreated water as it enters the treatment plant from a well, intake, or reservoir. Its quality determines the chemicals, processes, and monitoring needed.

Adding a chemical such as alum to raw water so that tiny suspended particles lose their repelling charges and begin to clump together. It is the first step in removing turbidity.

Slow, gentle mixing that causes small particles formed during coagulation to collide and grow into larger, heavier clumps called floc that can settle.

A settling process in which water moves slowly through a basin so heavier floc and particles sink to the bottom and are removed as sludge.

Passing water through beds of granular material such as sand and anthracite to remove remaining particles, floc, and some microorganisms. It is a critical barrier against pathogens.

Reversing the normal flow of water upward through a filter at a high rate to expand the media and wash out trapped solids. It restores filter capacity and is scheduled by head loss or time.

A bench-scale test using several beakers and different chemical doses to find the coagulant amount and pH that produce the best settling and lowest turbidity.

The granular layers inside a filter, commonly anthracite over sand with gravel support, that trap particles as water passes through. Media type and depth affect filtration.

The drop in pressure or water level as water moves through a filter or pipe because of friction and clogging. Rising head loss signals that a filter needs backwashing.

The flow through a settling basin divided by its surface area, expressed as gallons per day per square foot. It is a key design and performance measure for clarifiers.

The product of disinfectant concentration in milligrams per liter and the contact time in minutes. It is used to show that enough disinfection has been provided to inactivate pathogens.

Chlorine remaining in water that has not reacted with ammonia or other substances. It is the form usually measured in the distribution system to confirm continuing protection.

Chlorine that has reacted with ammonia or nitrogen compounds to form chloramines. It lasts longer than free chlorine but is a weaker disinfectant.

Chemicals such as trihalomethanes and haloacetic acids that form when chlorine reacts with natural organic matter. They are regulated because long-term exposure may harm health.

The amount of chlorine used up by organisms, metals, ammonia, and organic matter in water before any residual remains. It must be satisfied before free chlorine can protect the system.

The period that water is in contact with a disinfectant before it reaches the first customer. Longer contact time allows more pathogen inactivation and supports meeting CT requirements.

The energy of water expressed as the height it could be raised, combining elevation, pressure, and velocity. Pumps must overcome static head plus friction head.

A graph supplied by the manufacturer showing the flow a pump delivers at various heads. The point where it crosses the system curve is the actual operating point.

Damage and noise caused when pressure drops so low that water vapor bubbles form and then collapse against a pump impeller. It reduces capacity and can destroy the pump.

A sharp pressure surge caused by a sudden change in flow, such as fast valve closure or pump shutdown. It can break pipes and is controlled by slow operation and surge protection.

A storage basin for filtered water after treatment and before pumping into the distribution system. It also provides chlorine contact time and helps meet peak demand.

A raised tank that uses gravity to maintain pressure and supply water during high demand or power outages. Its water level reflects system pressure.

A pump placed within the distribution system to increase pressure or move water into higher-service areas or storage tanks. It is often controlled by pressure settings.

Any actual or potential link between drinking water piping and a source of nonpotable water, such as a hose or irrigation line. It can allow backflow contamination.

The highest concentration of a regulated contaminant allowed in water delivered to customers, set as close to the health goal as practical. It is enforceable under the Safe Drinking Water Act.

An enforceable required procedure or process, such as filtration or corrosion control, used when a contaminant cannot be reliably measured as an MCL. Failure to perform it is a violation.

An annual report that community water systems must give customers describing source water, detected contaminants, and compliance with drinking water standards. It is also called a right-to-know report.

An on-site review of a water system's sources, treatment, storage, and distribution to find conditions that could contaminate drinking water. States use them to target oversight.

A space large enough to enter but with limited entry or exit, not designed for continuous occupancy, such as a clear well or vault. Entry requires testing, permits, and attendants.

The theoretical average time water spends in a tank, calculated as tank volume divided by flow rate. It is used for chlorine contact and settling design.

Required notice to customers when a water system violates a drinking water standard or faces a significant risk. The form and deadline depend on how serious the problem is.