Water Glossary: M

MAF Million acre-feet.
MCL Maximum contaminant level. According to health agencies, the maximum amount of a substance that can be present in water that's safe to drink and which looks, tastes, and smells good.
MGD Million gallons per day, a measure used for water treatment plants and other facilities.
microbiological Relating to microorganisms and their life processes.*
microorganism An organism of microscopic size, such as bacterium.
mitigation A way in which an agency may offset negative environmental impacts of a project or make the impacts less serious.
monitoring Scrutinizing and checking systematically with a view to collecting data
MTBE Methyl tertiary butyl ether. An oxygenate used in California gasoline to help prevent air pollution. The chemical has a long life and has been determined to have polluted lakes, reservoirs and groundwater after leaking from watercraft, underground tanks, and pipelines. Required to be phased out by Dec. 31, 2002.
mulch Material spread on the ground to reduce soil erosion and evaporation of water; include hay, plastic sheeting, and wood chips.
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*Reprinted from The Drinking Water Dictionary, by permission. Copyright © 2000, American Water Works Association