Terminology
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.
Advanced oxidation: Oxidation processes relying on hydroxyl radical oxidation to destroy recalcitrant contaminants.
Advanced treatment: Additional treatment provided to remove suspended and dissolved substances that persist through conventional secondary treatment. Often this term is used to mean additional treatment after tertiary treatment for the purpose of further removing contaminants of concern to public health. In many cases, this includes membrane filtration, reverse osmosis (RO), and advanced oxidation/disinfection with ultraviolet light (UV) and hydrogen peroxide (H₂O₂).
Agriculture: The science, art, and business of cultivating the soil, producing crops, and raising livestock (farming).
Aquifer: An underground layer of sand, gravel, or rock through which water can pass and is stored. Aquifers supply the water for wells and springs.
Augmentation: The process of adding recycled water to an existing raw water supply (such as a reservoir, lake, river, wetland, and/or groundwater basin) after receiving advanced treatment. This water could eventually be used for drinking water after further treatment.
Backflow prevention: Prevention of the flow of any foreign liquids, gases, or substances into the distribution pipelines of a potable water supply; accomplished by an air gap or mechanical backflow obstacle.
Biochemical oxygen demand (BOD): A measure of the amount of oxygen consumed in the biological processes that break down organic matter in water. Used as an indicator of the amount of organic material in the waste stream. The greater the BOD, the greater the degree of pollution. Usually expressed in milligrams per liter.
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.
Clean Water Act: The federal law that establishes how the United States will restore and maintain the chemical, physical, and biological integrity of the country’s waters (oceans, lakes, streams and rivers, groundwater, and wetlands).
Climate: Meteorological conditions, including temperature, precipitation, condensation, and wind.
Central Arizona Project (CAP) canal: A canal structure that delivers water to various municipalities (or jurisdictions) from the Colorado River to Southern Arizona.
Conservation: Obtaining the benefits of water more efficiently, resulting in reduced demand for water. Sometimes called “end-use efficiency” or “demand management.”
Dam: A structure built to hold back water.
Direct injection: Injecting recycled water through an injection well directly into a groundwater basin. If the water will later be used for drinking, the recycled water will receive advanced treatment prior to injection.
Direct potable reuse (DPR): The immediate use of recycled water as a potable water supply. DPR differs from indirect potable reuse since the environmental buffer characteristic of IPR applications is eliminated.
Disinfection: Water treatment which destroys or inactivates potentially harmful bacteria.
Drought: A long period of below-average precipitation.
Ecosystem: A community of plants and animals and the physical environment in which they live.
Effluent: The water leaving a wastewater treatment plant. If the effluent has been treated to a sufficiently high standard, it may be used for recycled water applications.
Endangered Species Act: The federal law that sets forth how the United States will protect and recover animal and plant species whose populations are in dangerous decline or close to extinction. The law protects not only threatened and endangered species but also the habitat upon which those species depend.
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 the federal National Environmental Policy Act for federal permitting or use of federal funds.
Estuary: The shallow water areas of bays or the mouths of rivers and creeks that discharge to the ocean or sea, where ocean tides meet and mix with fresh water.
Eutrophication: The deterioration of an aquatic ecosystem due to high nutrient loads that lead to algal blooms, oxygen depletion, noxious odors, and a loss of biodiversity.
Filtration: A process that separates small particles from water by using a porous barrier to trap the particles while allowing the water to pass.
Finished water: Treated drinking water that is considered safe and suitable for delivery to consumers.
Gray water: Water that has been used for showering, clothes washing, and faucet uses. Kitchen sink and toilet water are excluded.
Groundwater: Water found below the surface of the Earth.
Hydrologic cycle: The movement of water as it evaporates from rivers, lakes, or oceans, returns to the earth as precipitation, and either flows into rivers and evaporates again or percolates through the soil to join groundwater or surface water. Also known as the water cycle.
Imported water: Water that originated in one hydrologic region and is transferred to another hydrologic region.
Indirect potable reuse (IPR): The blending of advanced treated recycled water into a natural water source (environmental buffer such as a groundwater basin or reservoir) that could be used for drinking water after further treatment.
Integrated resource planning (IRP): A method for looking ahead using environmental, engineering, social, financial, and economic considerations; includes evaluating both supply and demand options while involving customers and other stakeholders.
Irrigation: Diverting or moving water from its natural course for use on crops or landscapes.
Maximum contaminant level (MCL): The highest allowable amount of a constituent in water, established by the U.S. Environmental Protection Agency under the Safe Drinking Water Act.
Micrograms per liter (µg/L): A measurement describing the amount of a substance in a liter of water. One µg/L equals one part per billion.
Milligrams per liter (mg/L): A measurement describing the amount of a substance in a liter of water. One mg/L equals one part per million.
Nanograms per liter (ng/L): A measurement describing the amount of a substance in a liter of water. One ng/L equals one part per trillion.
Million gallons per day (MGD): A measure of flow describing the volume of water treated or discharged by a facility in one day.
Microfiltration: A physical separation process using tiny hollow membranes to separate particles from water, often used as pretreatment for reverse osmosis.
Nanofiltration: A membrane filtration process most often used with low total dissolved solids water to soften water and remove disinfection by-product precursors. Commonly used with desalination.
National Pollutant Discharge Elimination System (NPDES): A federal permit authorized by the Clean Water Act that regulates pollutant discharges to surface waters of the United States.
Nephelometric turbidity unit (NTU): A unit of measure related to the particles suspended in water.
Non-potable: Water not suitable for drinking.
Non-potable reuse: Recycled water applications not intended for drinking.
Parts per billion (ppb): A unit of measure for contamination concentration. One thousand ppb equals one ppm.
Parts per million (ppm): A unit of measure for contamination concentration. One ppm equals one milligram per liter.
Pathogens: Disease-causing organisms such as viruses, bacteria, protozoa, or fungi.
Percolation pond: A pond that allows water to seep through layers of soil and rock, cleaning the water as it moves downward and recharges an aquifer.
Pharmaceutically active compounds (PhACs): Compounds such as hormones, antibiotics, and painkillers that enter the environment at low concentrations through human use.
Potable: Water that is safe for human consumption.
Potable reuse: The use of advanced treated recycled water to augment a potable water distribution system.
Pharmaceuticals and personal care products (PPCPs): Products such as medications, soaps, shampoos, and other household chemicals that enter wastewater at low concentrations.
Pretreatment: A wastewater treatment process that removes large debris using metal screens.
Primary treatment: The first stage of wastewater treatment where suspended solids are removed.
Raw water: Untreated water.
Reclaimed water: Wastewater treated to a level that allows reuse for a beneficial purpose.
Recycled water: Water reused before returning to the natural water cycle; also known as reclaimed water.
Reservoir: A body of water or storage structure used to collect and store water.
Retrofit: Construction or modification of infrastructure to separate potable and recycled water pipelines.
Reuse: The act of using water again for beneficial purposes before it returns to the hydrologic cycle.
Reverse osmosis (RO): A process that removes salts and impurities by forcing water through a semi-permeable membrane.
Safe Drinking Water Act (SDWA): Federal legislation regulating drinking water quality and contaminant reduction.
Salinity: The concentration of dissolved mineral salts in water.
Seawater intrusion: The movement of saltwater into freshwater systems.
Secondary treatment: Wastewater treatment that removes organic matter and pathogens to a non-potable level.
Soil aquifer treatment (SAT): Purification of water through percolation into an underground aquifer.
Storage: Water held in a reservoir for later use.
Surface water: Water located on the Earth’s surface.
Total dissolved solids (TDS): A measure of minerals dissolved in water.
Total suspended solids (TSS): A measure of suspended particles in water or wastewater.
Tertiary treatment: Advanced wastewater treatment beyond secondary treatment to remove specific pollutants.
Turbidity: A measure of water cloudiness caused by suspended particles.
Ultrafiltration (UF): A membrane filtration process between microfiltration and reverse osmosis.
Ultraviolet treatment (UV): Use of ultraviolet light for disinfection or advanced oxidation.
Urban runoff: Water from urban areas that flows into storm drains or waterways.
Wastewater: Water that has been used and degraded in quality by human activity.
Water cycle: The continuous movement of water through evaporation, precipitation, infiltration, and runoff.
Watershed: An area of land that drains water to a common point.
Wetlands: Areas with saturated soils that support water-adapted vegetation.
Xeriscape: A landscaping approach using plants suited to local climate and requiring minimal water.
References
Columbia Analytical Services, 2011. (Website) Accessed December 2011. http://www.caslab.com/
Letterman, R., 1999. “Water Quality and Treatment.” 5th Ed. New York: American Water Works Association and McGraw-Hill.
WateReuse Association, 2011. Sustainable Solutions for a Thirsty Plant (Website). Accessed October 2011. http://www.watereuse.org/information-resources/about-water-reuse/faqs-0