Glossary of Water and Wastewater Terms

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5 random terms from our glossary

polarization

The concentration of ions in the thin, boundary layer adjacent to a membrane or pipe wall.

activated sludge

Sludge particles produced in raw or settled wastewater (primary effluent) by the growth of organisms in aeration tanks in the presence of dissolved oxygen (DO). These sludge particles contain living organisms that feed on the incoming wastewater.

set point

The position at which the control or controller is set. This is the same as the desired value of the process variable. For example, a thermostat is set to maintain a desired temperature.

litmus paper

A strip of paper that is chemically treated with a dye named litmus. This strip is placed in the liquid whose pH is being determined. The use of litmus paper, which is red at any pH less than 5 and blue at any pH greater than 8, allows an inspector to determine only whether a solution is acidic or basic. More precise pH determinations can be found by using pH test paper, which compares subtle color differences to a color chart to indicate pH level.

noble metal

A chemically inactive metal (such as gold). A metal that does not corrode easily and is much scarcer (and more valuable) than the so-called useful or base metals. Also see BASE METAL.