Terminology - Recycled Water Words

The following list is provided for general information only and uses non-technical language. It should not be considered a complete list of all terminology used in the recycled water industry. The definitions do not supply all the technical information available for the term or word.

For additional information about water recycling, please visit the City of San Diego's Recycled Water Program website www.sandiego.gov/water/recycled.

Acre-foot A unit used to measure large volumes of water. It equals the volume of water required to cover one acre to a depth of one foot. An acre-foot is 325,851 gallons and is considered enough water to meet the needs of two average-sized families with a house and yard for one year.

Augmentation Adding recycled water or advanced treated recycled water (repurified water) to an existing raw water supply; such as a lake, river, wetland and/or groundwater basin.

Beneficial reuse The use of recycled water for purposes that contribute to the economy or environment of a community.

Blending Mixing or combining one water source with another.

Brackish water Water that has a higher salt content than fresh water, but not as high as sea water. Usually, the salts must be removed or greatly reduced before the water is usable.

Desalination The process of removing minerals and other components from non-potable water, usually referred to as sea water or brackish groundwater desalination. There are several available treatment processes for desalination; reverse osmosis and flash distillation are the most common.

Direct reuse Using recycled water that has been transported directly from a water recycling facility to a reuse location. The recycled water does not pass through a natural body of either surface water or groundwater before it reaches the reuse location.

Disinfection The process of killing a large portion of microorganisms in or on a substance. Water recycling facilities may use chlorine, ultraviolet light or ozone to disinfect the recycled water in the final (tertiary) processing stage.

Drinking water (Potable water) Water that has been treated to a level sufficient to meet federal drinking water standards as well as state and local water quality standards and is designated safe for human consumption.

Drought A defined period of time when rainfall and runoff in a geographic area are much less than average.

Graywater Wastewater from a household or small commercial establishment that does not include wastewater from a toilet, kitchen sink, dishwasher or water used for washing diapers. In San Diego, graywater systems require permits from regulatory agencies. At single family residences, the systems typically collect shower/tub water and non-kitchen sink water and use this water for outdoor irrigation delivered by underground piping.

Ground/water/groundwater basin Water beneath the earth's surface that supplies wells and natural springs. A groundwater basin is an underground area that contains large amounts of water.

Groundwater recharge Naturally or artificially adding water back into a groundwater basin. Recharge may be needed because a groundwater basin is diminished or threatened by supply or quality issues.

Indirect reuse The process of taking recycled water from a water recycling facility and putting it into the natural environment (groundwater basins, open reservoirs, streams) instead of distributing it directly to a reuse site. The treatment level of the recycled water intended for indirect reuse is dependent on various considerations.

Non-contact recreation Recreational activities that do not have a significant risk of water ingestion, including fishing, commercial and recreational boating and have limited risk of body contact from shoreline activities.

Non-potable water Water that is not suitable for drinking because it has not been treated to drinking water standards.

Potable water (Drinking water) Water that is naturally drinkable or has been treated to a level sufficient to meet federal drinking water standards as well as state and local water quality standards and is safe for human consumption.

Primary, secondary and tertiary treatment The stages in a wastewater treatment facility that clean wastewater to a level where it can be safely discharged into the environment. The production of recycled water requires at least all three of these treatment stages.

For a schematic and explanation of these treatment levels, please visit the North City Water Reclamation Plant

Raw water Water that has not been treated for use. Examples of raw water are water in the Colorado River aqueduct, the State Water Project aqueduct, open reservoirs (whether filled with imported water or runoff), rivers, naturally occurring lakes and some well water.

Recycled water or reclaimed water (terms are interchangeable) Water that originated as municipal wastewater and has undergone a high level of treatment at a reclamation facility so that it can be beneficially reused for a variety of purposes. The degree of treatment for recycled water depends on the water quality needed for the specific use and for public health protection.

Repurified water As the term is used in California, recycled water that has been treated to an advanced level beyond tertiary treatment, so that it can be added to water supplies ultimately used for potable water. Repurified water may be discharged into a surface water reservoir or groundwater basin that supplies water directly to a water treatment facility. The water treatment facility supplies a water delivery system serving domestic uses, including drinking water.

Reservoir augmentation The process of adding repurified water to a surface water reservoir. The recycled water receives advanced treatment processes (for example, reverse osmosis), is then is stored in an open reservoir for a specified minimum time (for example, one year). In the reservoir, the repurified water blends with untreated water in the reservoir. The blended water is then treated and disinfected at a conventional surface water treatment plant and is distributed into the drinking water delivery system.

Reverse osmosis A method of removing dissolved salts and other constituents from water. Pressure is used to force the water through a semi-permeable membrane that will transmit the water but stop most dissolved materials from passing through.

Title 22 Standards Requirements established by the California Department of Health Services for the production and use of recycled water. Title 22, Chapter 3, Division 4 of the California Code of Regulations, outlines the level of treatment required for allowable uses for recycled water. The most typical uses include irrigation, fire fighting, residential landscape watering, industrial uses, food crop production, construction activities, commercial laundries, toilet flushing, road cleaning, recreational purposes, lakes, ponds and decorative fountains.

Total dissolved solids (TDS) Substances that exist as a solid when dry and dissolve completely in water, such as ordinary table salt. Before recycled water can be beneficially used, the level of total dissolved solids must be appropriate for the specific use.

Water reuse The planned use of recycled water for a specific beneficial purpose.

Wetland An area supporting plant and animal life that is inundated or saturated by water on an annual or seasonal basis. A wetland can protect endangered species, filter pollutants in streams, provide flood control, prevent erosion, and may provide recreational opportunities.