A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
ACRE-FOOT: A volume of water equal to one foot in depth covering an area of one acre, or 43,560 cubic feet; approximately 325,851 gallons.
BIOFOULING: The formation of bacterial film (biofilm) on fragile reverse osmosis membrane surfaces.
BRACKISH WATER: Water containing dissolved minerals in amounts that exceed normally acceptable standards for municipal, domestic, and irrigation uses. Considerably less saline than seawater.
CLIMATE: Meteorological conditions, including temperature, precipitation, condensation and wind.
CONCENTRATE: Water that contains a high concentration of salt. Concentrate discharges from desalination plants may include constituents used in pretreatment processes, in addition to the high salt concentration seawater.
CONSERVATION: Obtaining the benefits of water more efficiently, resulting in reduced demand for water. Sometimes called "end-use efficiency" or "demand management."
DESALINATION: Specific treatment processes, such as reverse osmosis or multi-stage flash distillation, to demineralize seawater or brackish (saline) waters to purify for drinking. Also sometimes used in wastewater treatment to remove salts and other pollutants.
DISINFECTION: Water treatment which destroys potentially harmful bacteria.
DISTILLATION: A process of desalination where the intake water is heated to produce steam. The steam is then condensed to produce product water with low salt concentration.
DROUGHT: A long period of below-average precipitation
ECOSYSTEM: A community of plants and animals and the physical environment in which they live.
ELECTRODIALYSIS: Most of the impurities in water are present in an ionized (electrically-charged) state. When an electric current is applied, the impurities migrate towards the positive and negative electrodes. The intermediate area becomes depleted of impurities and discharges a purified stream of product water. This technology is used for brackish waters but is not currently available for desalting seawater on a commercial scale.
ENDOCRINE DISRUPTING COMPOUNDS (EDCs): Chemicals that can interfere with the normal hormone function in humans and animals.
ENVIRONMENTAL IMPACT STATEMENT (EIS): Detailed analysis of the impacts of a project on all aspects of the natural environment required by federal National Environmental Policy Act for federal permitting or use of federal funds.
FEEDWATER: Water fed to desalination equipment. This can be source water with or without pretreatment.
FILTRATION: A process that separates small particles from water by using a porous barrier to trap the particles and allowing the water through.
FINISHED WATER: Treated drinking water that is considered safe and suitable for delivery to consumers.
HYDROLOGIC CYCLE: The movement of water as it evaporates from rivers, lakes or oceans, returns to the earth as precipitation, flows into rivers and evaporates again.
INTEGRATED RESOURCE PLANNING (IRP): A method for looking ahead using environmental, engineering, social, financial and economic considerations; includes using the same criteria to evaluate both supply and demand options while involving customers and other stakeholders in the process.
MAXIMUM CONTAMINANT LEVEL: The highest allowable amount of a constituent in water. Drinking water quality criteria are established by the U.S. Environmental Protection Agency as regulatory standards.
mg/L: Milligrams per liter; a measurement describing the amount of a substance (such as a mineral, chemical or contaminant) in a liter of water. One milligram per liter is equal to one part per million.
MGD: Abbreviation for million gallons per day. This term is used to describe the volumes water treated and discharged from a treatment plant.
MICROFILTRATION: A physical separation process where tiny, hollow straw-like membranes separate particles from water. It is used as a pretreatment for reverse osmosis.
NPDES: National Pollutant Discharge Elimination System. A federal permit authorized by the Clean Water Act, Title IV, which is required for discharge of pollutants to navigable waters of the United States, which includes any discharge to surface waters-lakes, streams, rivers, bays, the ocean, wetlands, storm sewer, or tributary to any surface water body.
PARTS PER BILLION: A unit frequently used to measure contamination concentration (parts of contamination per billion parts of water). One thousand parts per billion is equal to one part per million.
PARTS PER MILLION: A unit used to measure contamination concentration (parts of contamination per million parts of water). One part per million is equal to one milligram per liter. (This term is becoming obsolete as instruments measure smaller particles.)
PATHOGENS: Disease-causing organisms (generally viruses, bacteria, protozoa, or fungi).
PhACs: Pharmaceutically-active compounds.
POTABLE: Water that does not contain pollution, contamination, objectionable minerals or infective agents and is considered safe for domestic consumption; drinkable.
REVERSE OSMOSIS: A method of removing salts or other impurities from water by forcing water through a semi-permeable membrane.
SAFE DRINKING WATER ACT (SDWA): Federal legislation passed in 1974 that regulates the treatment of water for human consumption and requires testing for and elimination of contaminants that might be present in the water.
SALINITY: Generally, the concentration of mineral salts dissolved in water. Salinity may be measured by weight (total dissolved solids - TDS), electrical conductivity, or osmotic pressure. Where seawater is known to be the major source of salt, salinity is often used to refer to the concentration of chlorides in the water.
SCALING: Salt deposits on the interior surfaces of a desalination plant.
STORAGE: Water held in a reservoir for later use.
TDS: Total dissolved solids. A quantitative measure of the residual minerals dissolved in water that remain after evaporation of a solution. Usually expressed in milligrams per liter.
TURBIDITY: A measure of suspended solids in water; cloudiness.
ULTRAFILTRATION (UF): A membrane filtration process that falls between reverse osmosis (RO) and microfiltration (MF) in terms of the size of particles removed.
ULTRAVIOLET TREATMENT (UV): The use of ultraviolet light for disinfection.
Water Cycle: The movement of water as it evaporates from rivers, lakes or oceans, returns to the earth as precipitation, flows into rivers and evaporates again.
µg/L (micrograms per liter): Micrograms per liter; a measurement describing the amount of a substance (such as a mineral, chemical or contaminant) in a liter of water. It is expressed in terms of weight per volume. One µg/L is equal to one part per billion.