Glossary of Water and Wastewater Terms

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5 random terms from our glossary

Altitude Valve

A valve that automatically shuts off the flow into an elevated tank when the water level in the tank reaches a predetermined level. The valve automatically opens when the pressure in the distribution system drops below the pressure in the tank.

Gas/Liquid

Gaseous/Liquid. Gaseous/liquid chlorination refers to the fact that free chlorine is delivered to small treatment plants in containers that hold liquid chlorine with a free chlorine gas above the liquid in the container. The release of chlorine gas from the liquid chlorine surface depends on the temperature of the liquid and the pressure of the chlorine gas on the liquid surface. As chlorine gas is removed from the container, the gas pressure drops and more liquid chlorine becomes chlorine gas.

Chronic Health Effect

An adverse effect on a human or animal body with symptoms that develop slowly over a long period of time or that recur frequently.

Sludge Volume Index (SVI)

A calculation that indicates the tendency of activated sludge solids (aerated solids) to thicken or to become concentrated during the sedimentation/thickening process. SVI is calculated in the following manner: (1) allow a mixed liquor sample from the aeration basin to settle for 30 minutes; (2) determine the suspended solids concentration for a sample of the same mixed liquor; (3) calculate SVI by dividing the measured (or observed) wet volume (mL/L) of the settled sludge by the dry weight concentration of MLSS in grams/L.

Superfund Act

See CERCLA.