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Water glossary



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Water Glossary - D

  • Dam: A structure of earth, rock, concrete, or other materials designed to retain water, creating a pond, lake, or reservoir.

  • Dealkalinisation: Any process that serves to reduce the alkalinity of water.

  • Decant: To draw off the upper layer of liquid after the heaviest material (a solid or another liquid) has settled.

  • Decarbonation: The process of removing carbon dioxide from water, using contact towers or air scrubbers.

  • Decomposition: The break down of organic matter by bacteria and fungi, to change the chemical structure and physical appearance of matter.

  • Decreasing block rate: Pricing that reflects per-unit costs of production and delivery that go down as customers consume more water.

  • Defluoridation: The removal of fluoride from drinking water to prevent teeth damage.

  • De-foaming agents: Chemicals that are added to wastewater discharges to prevent the water from foaming when it is discharged into a receiving water body.

  • Degasification: The process of removing dissolved gasses from water, using vacuum or heat.

  • Deionisation: Process that serves to remove all ionized substances from a solution. Most commonly is the exchange process where cations and anions are removed independently of each other.

  • Deionized water: Common industrial water used to remove contaminants from products and equipment.

  • Delivery/release: The amount of water delivered to the point of use and the amount released after use; the difference between these amounts is usually the same as the consumptive use. See also consumptive use.

  • Delta: A fan-shaped alluvial deposit at a river mouth formed by the deposition of successive layers of sediment.

  • Demand: The numerical expression of the desire for goods and services associated with an economic standard for acquiring them.

  • Demineralization: A process to remove minerals from water, usually the term is restricted to ion exchange processes.

  • Demiwater: Demineralized water. Water that is treated to be contaminant-, mineral- and salt free.

  • Denitrification: Removal of nitrate and nitrate product from water to produce a quality that answers common water standards.

  • Density: The weight of a certain amount of water. It is usually expressed in kilograms per cubic metre.

  • Dental fluorosis: Disorder caused by excessive absorption of fluorine and characterized by brown staining of teeth.

  • Depletion: Loss of water from surface water reservoirs or groundwater aquifers at a rate greater than that of recharge.

  • Deposit: Something dropped or left behind by moving water, as sand or mud.

  • Depression storage: The storage of water in low areas, such as ponds, and wetlands.

  • Depth filtration: Treatment process in which the entire filter bed is used to trap insoluble and suspended particles in its voids as water flows through it.

  • Desalination: The removal of salts from water. The three primary types of desalination are: (1) distillation, (2) electrodialysis processes, and (3) reverse osmosis processes.

  • Desorption: The opposite of adsorption; the release of matter from the adsorption medium, usually to recover material.

  • Detection limit: The lowest level that can be determined by a specific analytical procedure or test method.

  • Detention time: The actual time that a small amount of water is in a settling basin or flocculating basin. In storage reservoirs, it means the length of time water will be stored.

  • Detergent: A water-soluble cleansing agent, other than soap.

  • Dewater: The separation of water from sludge, to produce a solid cake.

  • Dewatering: The deliberate attempt to lower the ground-water level in or below land surface for selected purposes such as agricultural, construction, mining or other activities. For mining operation, dewatering usually is accomplished by pumping the water out of the ground and discharging to a surface-water body. However, some dewatering involves gravity feeding water from the surficial aquifer into a deeper aquifer through recharge wells.

  • Diatomaceous: Consisting of or abounding in diatoms, a class of unicellular or colonial algae having a silicified cell wall that persists as a skeleton after death.

  • Diffuser: A component of the ozone contacting system in an ozone generator that allows diffusion of an ozone containing gas.

  • Diffusion: The movement of gas molecules or aerosols into liquids, caused by a concentration gradient.

  • Digester: A closed tank for wastewater treatment, in which bacterial action is induced to break down organic matter.

  • Diluting water: Distilled water that has been stabilized, buffered, and aerated. Used in the BOD test.

  • Dioxin: Any of a family of compounds known chemically as dibenzo-p-dioxins. Concern about them arises from their potential toxicity and contamination in commercial products.

  • Direct run-off: Water that flows from the ground surface directly into streams, rivers, and lakes.

  • Discharge: In the simplest form, discharge means outflow of water. The use of this term is not restricted as to course or location, and it can be used to describe the flow of water from a pipe or from a drainage basin. Other words related to it are runoff, streamflow, and yield.

  • Discharge permit: A permit issued by a state or the federal government to discharge effluent into waters of the state or the United States. In many states both State and federal permits are required.

  • Disinfectants: Fluids or gasses to disinfect filters, pipelines, systems, etc.

  • Disinfection: The killing of the larger portion of the harmful and objectionable bacteria in the sewage. Usually accomplished by introduction of chlorine, but more and more facilities are using exposure to ultraviolet radiation, which renders the bacteria sterile.

  • Disinfection byproducts: Halogenated organic chemicals formed when water is disinfected.

  • Dispersion: The movement and spreading of contaminants out and down in an aquifer.

  • Displacement: Distance by which portions of the same geological layer are offset from each other by a fault.

  • Dissolve: The process by which solid particles mix molecule by molecule with a liquid and appear to become part of the liquid.

  • Dissolved air flotation (DAF): A procedure of induced flotation with very fine air bubbles or 'micro bubbles', of 40 to 70 microns.

  • Dissolved oxygen (DO): Amount of oxygen gas dissolved in a given quantity of water at a given temperature and atmospheric pressure. It is usually expressed as a concentration in parts per million or as a percentage of saturation.

  • Dissolved solids: Inorganic material contained in water or wastes. Excessive dissolved solids make water unsuitable for drinking or industrial uses. See TDS.

  • Dissolved solids (DS): Very small pieces of organic and inorganic material contained in water. Excessive amounts make water unfit to drink or limit its use in industrial processes.

  • Distillation: Water treatment method where water is boiled to steam and condensed in a separate reservoir. Contaminants with higher boiling points than water do not vaporize and remain in the boiling flask.

  • Distilled water: Water that has been treated by boiling and condensation to remove solids, inorganics, and some organic chemicals.

  • Diversion: The transfer of water from a stream, lake, aquifer, or other source of water by a canal, pipe, well, or other conduit to another watercourse or to the land, as in the case of an irrigation system.

  • Domestic use: The quantity of water used for household purposes such as washing, food preparation, and bathing.

  • Domestic wastewater facility: Facilities that receive or dispose of wastewater derived principally from residential dwellings, business or commercial buildings, institutions, and the like. Can also include some wastewater derived from industrial facilities. May also be referred to as a municipal wastewater facility.

  • Domestic water use: Water for household purposes, such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens. Also called residential water use. The water may be obtained from a public supply or may be self supplied. See also public supply and self-supplied water.

  • Drainage area: Of a stream at a specified location is that area, measured in a horizontal plane, enclosed by a topographic divide from which direct surface runoff from precipitation normally drains by gravity into the stream above the specified location.

  • Drainage basin: See: Watershed.

  • Dredgeate: The material excavated from lake, river, or channel bottoms during dredging.

  • Dredging: The removal of material from the bottom of water bodies using a scooping machine. This disturbs the ecosystem and causes silting that can kill aquatic life.

  • Driller's well log: A log kept at the time of drilling showing the depth, thickness, character of the different strata penetrated, location of water-bearing strata, depth, size, and character of casing installed.

  • Dripstone: Deposits of calcium carbonate that include stalactites, stalagmites, columns, and cave pearls.

  • Drop tubes: Devices that can be added to a center pivot system to achieve greater efficiency in agricultural irrigation.

  • Drought: Although there is no universally accepted definition of drought, it is generally the term applied to periods of less than average precipitation over a certain period of time. In south Texas ranchers say drought begins as soon as it stops raining.

  • Dry cooling: Cooling-down process using steam, to eliminate the loss of water.

  • Dry deposition: Emissions of sulfur and nitrogen oxides that, in the absence of water in the atmosphere (i.e., rain), settle to the ground as particulate matter.

  • Duplicates: Two separate samples with separate containers taken at the same time at the same place.

  • Dyke: An artificial embankment constructed to prevent flooding.

  • Dystrophic lakes: Acidic bodies of water that contain many plants but few fish, due to the presence of great amounts of organic matter.

Water glossary