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Absolute The micron rating of a filter. It indicates that any particle larger than a specific size will be trapped within the filter. Absorption When a solid takes up molecules into its structure. Acid aerosol Very small liquid or solid particles that are acidic and are small enough to become airborne. Acid neutralizing capacity Measure of the buffering capacity of water; the ability of water to resist changes in pH. Rain that has a flamboyantly low pH, due to contact with atmospheric pollutants such as sulphuric oxides. Acidity The quantitative capacity of water to neutralize a base, expressed in ppm or mg/L calcium carbonate equivalent. The number of hydrogen atoms that are present determines this. It is usually measured by titration with a standard solution of sodium hydroxide. Activated coal This is the most commonly used adsorption medium, produced by heating carbonaceous substances or cellulose bases in the absence of air. It has a very porous structure and is commonly used to remove organic matter and dissolved gases from water. Its appearance is similar to coal or peat. Available in granular, powder or block form; in powder form it has the highest adsorption capacity. Activated sludge Oxygen dependent biological process that serves to convert soluble organic matter to solid biomass, that is removable by gravity or filtration. Active groups Really fixed ions bolted on to the matrix of an ion exchanger. Each active group must always have a counter-ion of opposite charge near itself. Adsorption Separation of liquids, gases, colloids or suspended matter from a medium by adherence to the surface or pores of a solid. Advanced oxidation process One of several combination oxidation processes. Advanced chemical oxidation processes use (chemical) oxidants to reduce COD/BOD levels, and to remove both organic and oxidisable inorganic components. The processes can completely oxidise organic materials to carbon dioxide and water, although it is often not necessary to operate the processes to this level of treatment. A wide variety of advanced oxidation processes are available:
The level of water treatment that requires an 85-percent reduction in pollutant concentration, also known as tertiary treatment. Advanced Wastewater Treatment Any treatment of sewage water that includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids. Aerated lagoon A water treatment pond that speeds up biological decomposition of organic waste by stimulating the growth and activity of bacteria, which are responsible for the degradation. Aeration Technique that is used with water treatment that demands oxygen supply, commonly known as aerobic biological water purification. Either water is brought into contact with water droplets by spraying or air is brought into contact with water by means of aeration facilities. Air is pressed through a body of water by bubbling and the water is supplied with oxygen. Aeration tank A tank that is used to inject air into water. Aerobic A process that takes place in the presence of oxygen, such as the digestion of organic matter by bacteria in an oxidation pond. Aerosol Very small liquid or solid particles dispersed in air. Affinity The keenness with which an ion exchanger takes up and holds on to a counter-ion. Affinities are very much affected by the concentration of the electrolyte surrounding the ion exchanger. Agglomeration A process of bringing smaller particles together to form a larger mass. Aggressive water Water that is soft and acidic and can corrode plumbing, pipes and appliances. Algae Single- or multi-celled organisms that are commonly found in surface water, such as duckweed. They produce their own food through photosynthesis. The algae population is divided up into green algae and blue algae, of which the blue algae are very damageable to human health. Excessive algae growth may cause the water to have undesirable odours or tastes. Decay of algae diminishes oxygen supplies in the water. Algal blooms Periods of enlarged algal growths that affect water quality. Algal blooms indicate potentially hazardous changes in the chemistry of water. Aliquot A measured portion of a sample taken for analysis. One or more aliquots make up a sample. Alkalinity Alkalinity means the buffering capacity of water; the capacity of the water to neutralize itself. It prevents the water pH levels from becoming too basic or acid. It also adds carbon to water. Alkalinity stabilizes water at pH levels around 7. However, when the acidity is high in water the alkalinity decreases, which can cause harmful conditions for aquatic life. In water chemistry alkalinity is expressed in ppm or mg/L of equivalent calcium carbonate. Total alkalinity of water is the sum of all three sorts of alkalinity; carbonate, bicarbonate and hydroxide alkalinity. Alluvium Sediments deposited by erosion processes, usually by streams. Anaerobic A process that takes place in the absence of oxygen, such as the digestion of organic matter by bacteria in a UASB-reactor. Anion A negatively charged ion that results from the dissociation of salts, acids or alkali's in solution. Anode A site in electrolysis where metal goes into solution as a cation leaving behind an equivalent of electrons to be transferred to an opposite electrode, called a cathode. Aquatic Growing in water, living in water, or frequenting water. Aqueous Something made up of water. Aqueous solubility The maximum concentration of a chemical that dissolves in a given amount of water. Aquifer A layer in the soil that is capable of transporting a significant volume of groundwater. Aromatics A type of hydrocarbon that contains a ring structure, such as benzene and toluene. They can be found for instance in gasoline. Assimilation The ability of water to purify itself of pollutants. Assimilative Capacity The capacity of natural water to receive wastewaters or toxic materials without negative effects and without damage to aquatic life or humans who consume the water. Atom The smallest unit of matter that is unique to a particular element. They are the ultimate building blocks for all matter. Atomic number A specific number that differs for each element, equal to the number of protons in the nucleus of each of its atoms. Attenuation The process of reduction of a compound's concentration over time. This can be through absorption, adsorption, degradation, dilution or transformation. Attrition The action of one particle rubbing against the other in a filter media or ion exchange bed that can in time cause breakdown of the particles. Available chlorine A measure of the amount of chlorine available in chlorinated lime, hypochlorite compounds, and other materials. Backflow The flow of water in a medium in a direction opposite to normal flow. Flow is often returned into the system by backflow, if the wastewater in a purification system is severely contaminated. Back Pressure Pressure that can cause water to backflow into the water supply when a user's waste water system is at a higher pressure than the public system. Back siphonage Reverse seepage of water in a distribution system. Backwashing Reversing the flow of water back through the filter media to remove entrapped solids. Bacteria Microscopically small single-cell organisms, that reproduce by fission of spores.  |
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