GLOSSARY OF WATER AND WASTEWATER TERMS (Source: Operator Basics, Montana State University, 2005 http://watercenter.montana.edu/training/ob2005/default.htm) Absorption : The uptake of water or dissolved chemicals by a cell, organism, or other absorbing material (as tree roots absorb dissolved nutrients in the soil). Access Hatch : An entry way into a storage tank that facilitates inspection and maintenance. Acid : A substance that tends to lose a proton, dissolves in water with the formation of hydrogen ions, contains hydrogen that may be replaced by metals to form salts, and is highly corrosive. Acidic : The condition of water or soil which contains a sufficient amount of acid substances to lower the pH below 7.0. Acre-Foot : A volume of water that covers one acre to a depth of one foot, or 43,560 cubic feet. Action Level : acronym: AL The concentration of lead or copper in water which determines, in some cases, the treatment requirements for source water or corrosion control. Activated Carbon : Adsorptive particles or granules of carbon usually obtained by heating carbon (such as wood). These particles or granules have a high capacity to selectively remove certain trace and soluble materials from water. Activated Sludge : Sludge containing many living microorganisms, including bacteria, fungi and protozoa, that are sustained by dissolved oxygen and can feed on incoming wastewater. Acute : Occurring over a short period of time; used to describe brief exposures and effects which appear promptly after exposure. Acute Health Effect : An impact on health which occurs over a short period of time after exposure to a contaminant. Acute Illness : An illness occuring over a short period of time; used to describe brief exposures and effects which appear promptly after exposure. Adsorption : The collection of a gas, liquid, or dissolved substance on the surface or interface zone of another material. Aeration : 1: The process of adding air to water either by passing water through air or passing air through water. 2: The process of adding air to wastewater in order to provide dissolved oxygen for 1 aerobic bacterial treatment, freshen wastewater, and keep solids in suspension. 3: A mechanical transfer of atmospheric oxygen from the air to the wastewater to supply the needs of aerobic and facultative microorganisms. Aerobic : The condition in which free oxygen is dissolved in the water. Aerobic bacteria need free dissolved oxygen to live and multiply. Air Binding : The clogging of a filter, or pipe, or pump due to the presence of air released from water. Air entering the filter media is harmful to both the filtration and backwash processes. Air can prevent the passage of water during the filtration process and can cause the loss of filter media during the backwash process. Air Gap : An open vertical drop, or vertical empty space, that separates a drinking water supply to be protected from another water system in a water treatment plant or other location. This open gap prevents the contamination of drinking water by backsiphonage or backflow because there is no way raw water or any other water can reach the drinking water. Air Release/vacuum Breaker Valve : acronym: AVB Valves used to release trapped air or vacuums created in water pipelines. Air Relief Valve : Valve used to release air trapped in water pipelines to prevent excessively high pressure. Air Vent : A screened opening on the top of a gravity tank that lets the tank "breathe" as the tank is filled and emptied. Alarm System : Detects unacceptable low and/or high water levels in a gravity storage tank and sends a signal to operators. Algae : Microscopic plants that contain chlorophyll, live floating (suspended) in water or are attached to rocks, walls and other surfaces, and grow and multiply through photosynthesis. Algae produce oxygen during sunlight hours, use oxygen during darkness, and affect the pH and dissolved oxygen levels in waster. Algal Bloom : A sudden massive growth of algae in a wastewater lagoon, lake or reservoir. Alkali : Any of certain soluble salts, principally of sodium, potassium, magnesium, and calcium. It has the property of combining with acids to form neutral salts and may be used in a chemical water treatment process. Alkaline : The condition of water or soil which contains a sufficient amount of alkali substances to raise the pH above 7.0. 2 Alkalinity : The capacity of water to neutralize acids, imparted primarily by the water's content of carbonates, bicarbonates, and hydroxides. A characteristic of substances with a pH greater than 7. Alluvial Deposit : Relating to mud and/or sand deposited by flowing water. Alluvial deposits may occur after a heavy rain storm. Alluvium : Mud and/or sand deposited by flowing water, commonly formed in river valleys and deltas from materials washed down the river after a heavy rain storm. Altitude Valve : A valve that automatically shuts off the flow into an elevated tank when the water level in the tank reaches a predetermined level. It automatically opens when the pressure in the distribution system drops below the pressure in the tank. The valve is often used to fill a second tank. Amoebic Dysentery : An inflammation of the colon causing diarrhea of varying degrees of severity due to infection by the amoeba Entamoeba histolytica. Anaerobic : The condition in which there is no, or very little, free dissolved oxygen in the water. Anaerobic bacteria live in the absence of free oxygen and obtain energy through the fermentation process. Annular Space : The ring-shaped space located between the bore-hole of a well and the well casing. Anode : The positive pole or electrode of an electrolytic system, such as a battery. The anode attracts negatively charged particles or ions (anions). Apparent Color : Color of water caused by suspended and dissolved particles in the water. Aquifer : A natural underground layer of porous, water-bearing materials (sand, gravel), usually capable of yielding a large amount of water. Artesian : Water held under pressure in porous rock or soil confined by impermeable geologic formations. Also, see confined aquifer. Artesian Well : Water held under pressure in porous rock or soil confined by impermeable geologic formations; a free flowing well. Aseptic : Free from the living germs of disease, fermentation or putrefaction; sterile. Assembly : A group of mechanical parts that fit together to form a self-contained unit. 3 Autotrophic Bacteria : Bacteria that utilize carbon dioxide for their carbon source to synthesize all the organic molecules of the cell. Available Chlorine : The amount of chlorine available in compound chlorine sources compared with that of elemental (liquid or gaseous) chlorine. Average Daily Flow : The average of the highest and lowest measured flows entering into a wastewater treatment facility in a day. Back-Pressure : Occurs when normal flow in the distribution system is reversed due to an increase in the downstream pressure above the supply pressure. Back-Siphonage : Occurs when a negative pressure (below atmospheric pressure, or a vacuum) develops in the distribution system which can allow pollutants or contaminants to be siphoned into the water system. Backflow : The unwanted reverse flow of water in a public water supply system. Backwash : The process of reversing the flow of water back through the filter media to remove the entrapped solids. Backwashing : The process of reversing the flow of water back through the filter media to remove the entrapped solids. Bacteria : 1: Single-celled microorganisms that can exist either as independent (free-living) organisms or as parasites (dependent upon another organism for life). Examples are Acidophilus, found in yogurt, E. coli, found in the colon, and Streptococcus, the cause of strep throat. 2: Microorganisms that use organic material for food (heterotrophs) or carbon dioxide (autotrophs) for building blocks of cellular molecules and energy, and produce waste products. The three main types of bacteria are: aerobic, anaerobic and facultative anaerobic. Baffle : A flat board or plate, deflector, guide, or similar device constructed or placed in flowing water or slurry systems to cause more uniform flow velocities, to absorb energy, and divert, guide, or agitate liquids (water, chemical solutions, slurry, etc.). Ball Valve : A valve with a ball resting in a cylindrical seat. A hole is bored through the ball to allow water to flow when the valve is open. When the ball is rotated 90 degrees, the valve is closed. Barrel : The body of a fire hydrant. It can be classified as wet or dry. 4 Base : A substance that takes up or accepts protons, dissociates in water to produce hydroxyl (OH-) ions, reacts with metals, and is corrosive. Basic : The condition of water or soil which contains a sufficient amount of alkaline substances to raise the pH about 7.0. Bentonite : A light-colored valuable clay that expands with the addition of water and is used as a sealant in water wells, as oil-well drilling mud, as a liner in wastewater lagoons, and as a filler in the building, paper, soap, and pharmaceutical industries. Best Available Technology : acronym: BAT After examination for efficacy under field conditions and not solely under laboratory conditions, the best technology treatment techniques or other means which the Administrator finds are available (taking cost into consideration). Biochemical Oxygen Demand : acronym: BOD or BOD5 The amount of oxygen used by a population of microorganisms to aerobically decompose organic matter present in a sample in five days. BOD5 is used as a measure of the organic strength of wastewater. Biosolids : Organic wastewater solids that can be used for beneficial purposes after stabilization by such methods as composting or digestion. Blue-Green Algae : Varieties of algae characterized by their bluish-green color; also known as cyanobacteria. The presence of blue-green algae indicates unhealthy conditions in wastewater lagoon cells or surface waters such as lakes, reservoirs, streams.