Abiotic factors: Non living; moisture, soil, nutrients, fire, wind, temperature, climate.

Absolute filtration rating (largest particle passed): The diameter of the largest hard spherical particle that will pass through a filter under specified test conditions.

This is an indication of the largest opening in the filter cloth.

Absorption: The taking in or soaking up of one substance into the body of another by molecular or chemical action (as tree roots absorb dissolved nutrients in the soil).

Absorption Field: A system of properly sized and constructed narrow trenches partially filled with a bed of washed gravel or crushed stone into which perforated or open joint pipe is placed. The discharge from the septic tank is distributed through these pipes into trenches and surrounding soil. While seepage pits normally require less land area to install, they should be used only where absorption fields are not suitable and well-water supplies are not endangered. Acetogenic bacterium: Prokaryotic organism that uses carbonate as a terminal electron acceptor and produces acetic acid as a waste product. Acetylene-block assay: Estimates denitrification by determining release of nitrous oxide (N20) from acetylene-treated soil.

Acetylene-reduction assay: Estimates nitrogenase activity by measuring the rate of acetylene reduced to ethylene.

¿V-Acetylglucosamine and ¿V-Acetylmuramic acid: Sugar derivatives in the peptidoglycan layer of bacterial cell walls.

Acid: A substance that dissolves in water with the formation of hydrogen ions, contains hydrogen which may be replaced by metals to form salt, and/or is corrosive.

Acidity: The capacity of water or wastewater to neutralize bases. Acidity is expressed in milligrams per liter of equivalent calcium carbonate. Acidity is not the same as Ph.

Acidophile: Organism that grows best under acid conditions (down to a pH of 1). Acid soil: Soil with a pH value <6.6.

Actinomycete: Nontaxonomic term applied to a group of high G + C base composition, Gram-positive bacteria that have a superficial resemblance to fungi. Includes many but not all organisms belonging to the order Actinomycetales.

Activated sludge: Sludge particles produced in raw or settled wastewater (primary effluent) by the growth of organisms (including zoogleal bacteria) in aeration tanks in the presence of dissolved oxygen. The term "activated" comes from the fact that the particles are teeming with fungi, bacteria, and protozoa. Activated sludge is different from primary sludge in that the sludge particles contain many living organisms which can feed on the incoming wastewater.

Activation energy: Amount of energy required to bring all molecules in one mole of a substance to their reactive state at a given temperature. Active site: Region of an enzyme where substrates bind.

Adenosine triphosphate (ATP): Common energy-donating molecule in biochemical reactions. Also an important compound in transfer of phosphate groups.

Adsorption: The gathering of a gas, liquid, or dissolved substance on the surface or interface zone of another substance.

ADP: Adenosine diphosphate. See ATP.

Aeration: The process of adding air to water. In wastewater treatment, air is added to freshen wastewater and to keep solids in suspension.

Aeration tank: The tank where raw or settled wastewater is mixed with return sludge and aerated. This is the same as an aeration bay, aerator, or reactor.

Aerobe: An organism that requires free oxygen for growth.

Aerobic: (i) Having molecular oxygen as a part of the environment, (ii) Growing only in the presence of molecular oxygen, as in aerobic organisms, (iii) Occurring only in the presence of molecular oxygen, as in certain chemical or biochemical processes such as aerobic respiration.

Aerotolerant anaerobes: Microbes that grow under both aerobic and anaerobic conditions, but do not shift from one mode of metabolism to another as conditions change. They obtain energy exclusively by fermentation.

Air flow/air permeability: Measure of the amount of air that flows through a filter - a variable of the degree of contamination, differential pressure, total porosity, and filter area. Expressed in either cubic feet/minute/square foot or liters/minute/square centimeter at a given pressure.

Agar: Complex polysaccharide derived from certain marine algae that is a gelling agent for solid or semisolid microbiological media. Agar consists of about 70% agarose and 30% agaropectin. Agar can be melted at temperature above 100° C; gelling temperature is 40-50° C.

Agarose: Nonsulfated linear polymer consisting of alternating residues of D-galactose and 3,6-anhydro-L-galactose. Agarose is extracted from seaweed, and agarose gels are often used as the resolving medium in electrophoresis. Akinete: Thick-walled resting cell of cyanobacteria and algae.

Alkaline substance: Chemical compounds in which the basic hydroxide (OH-) ion is united with a metallic ion, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). These substances impart alkalinity to water and are employed for neutralization of acids. Lime is the most commonly used alkaline material in wastewater treatment.

Alga (plural, algae): Phototrophic eukaryotic microorganism. Algae could be unicellular or multicellular. Blue-green algae are not true algae; they belong to a group of bacteria called cyanobacteria.

Aliphatic: Organic compound in which the main carbon structure is a straight chain.

Alkaline soil: Soil having a pH value >7.3.

Alkalophile: Organism that grows best under alkaline conditions (up to a pH of 10.5).

Alkane: Straight chain or branched organic structure that lacks double bonds.

Alkene: Straight chain or branched organic structure that contains at least one double bond.

Allochthonous flora: Organisms that are not indigenous to the soil but that enter soil by precipitation, diseased tissues, manure, and sewage. They may persist for some time but do not contribute in a significant way to ecologically significant transformations or interactions.

Allosteric site: Site on the enzyme other than the active site to which a nonsubstate compound binds. This may result in a conformational change at the active site so that the normal substrate cannot bind to it.

Alum: Astringent crystalline double sulfate of an alkali. K2S04AL2 (S04)3 24H20. Used in the processing of pickles and as a flocking agent. Excess aluminum in the environment can be hazardous.

Amensalism (antagonism): Production of a substance by one organism that is inhibitory to one or more other organisms. The terms antibiosis and allelopathy also describe cases of chemical inhibition.

Ambient temperature: Temperature of the surroundings.

Amino group: An ~NH2 group attached to a carbon skeleton as in the amines and amino acids.

Ammonia oxidation: Test drawn during manufacturing process to evaluate the ammonia oxidation rate for the nitrifiers.

Ammonification: Liberation of ammonium (ammonia) from organic nitrogenous compounds by the action of microorganisms.

Amoeba (plural, amoebae): Protozoa that can alter their cell shape, usually by the extrusion of one or more pseudopodia.

Anabolism: Metabolic processes involved in the synthesis of cell constituents from simpler molecules. An anabolic process usually requires energy. Anaerobe: An organism that lives and reproduces in the absence of dissolved oxygen, instead deriving oxygen from the breakdown of complex substances.

Anaerobic: (i) Absence of molecular oxygen, (ii) Growing in the absence of molecular oxygen, such as anaerobic bacteria, (iii) Occurring in the absence of molecular oxygen, as a biochemical process.

Anaerobic respiration: Metabolic process whereby electrons are transferred from an organic, or in some cases, inorganic compounds to an inorganic acceptor molecule other than oxygen. The most common acceptors are nitrate, sulfate, and carbonate.

Anamorph: Asexual stage of fungal reproduction in which cells are formed by the process of mitosis.

Anhydrous: Very dry. No water or dampness is present.

Anion: A negatively charged ion in an electrolyte solution, attracted to the anode under the influence of a difference in electrical potential. Chloride is an anion.

Anion exchange capacity: Sum total of exchangeable anions that a soil can adsorb.

Expressed as centimoles of negative charge per kilogram of soil.

Anoxic: Literally "without oxygen." An adjective describing a microbial habitat devoid of oxygen.

Anoxygenic photosynthesis: Type of photosynthesis in green and purple bacteria in which oxygen is not produced.

Antagonist: Biological agent that reduces the number or disease-producing activities of a pathogen.

Antheridium: Male gametangium found in the phylum Oomycota (Kingdom Stramenopila) and phylum Ascomycota (Kingdom Fungi).

Anthropogenic: Derived from human activities.

Antibiosis: Inhibition or lysis of an organism mediated by metabolic products of the antagonist; these products include lytic agents, enzymes, volatile compounds, and other toxic substances.

Antibiotic: Organic substance produced by one species of organism that in low concentrations will kill or inhibit growth of certain other organisms.

Antibody: Protein that is produced by animals in response to the presence of an antigen and that can combine specifically with that antigen.

Antigen: Substance that can incite the production of a specific antibody and that can combine with that antibody.

Antiseptic: Agent that kills or inhibits microbial growth but is not harmful to human tissue.

Antistatic: Material that minimizes static charge generation, provides "controlled" static charge dissipation, or both.

API separator: A facility developed by the Committee on Disposal or Refinery Wastes of the American Petroleum Institute for separation of oil from wastewater in a gravity differential and equipped with means for recovering the separated oil and removing sludge.

Aromatic: Organic compounds which contain a benzene ring, or a ring with similar chemical characteristics.

Arthropod: Invertebrate with jointed body and limbs (includes insects, arachnids, and crustaceans).

Ascoma (plural, ascomata): Fungal fruiting body that contains ascospores; also termed an ascocarp.

Ascospore: Spores resulting from karyogamy and meiosis that are formed within an ascus. Sexual spore of the Ascomycota.

Ascus (plural, asci): Saclike cell of the sexual state formed by fungi in the phylum Ascomycota containing ascospores.

Aseptic: Free from living germs of disease, fermentation or putrefaction.

Aseptic technique: Manipulating sterile instruments or culture media in such a way as to maintain sterility.

Assimilate: To take in, similar to eating food.

Assimilatory nitrate reduction: Conversion of nitrate to reduced forms of nitrogen, generally ammonium, for the synthesis of amino acids and proteins.

Associative dinitrogen fixation: Close interaction between a free-living diazotrophic organism and a higher plant that results in an enhanced rate of dinitrogen fixation.

Associative symbiosis: Close but relatively casual interaction between two dissimilar organisms or biological systems. The association may be mutually beneficial but is not required for accomplishment of a particular function.

Attached growth processes: Wastewater treatment processes in which the microorganisms and bacteria treating the wastes are attached to the media in the reactor. The wastes being treated flow over the media. Trickling filters, bio-towers, and RBCs are attached growth reactors. These reactors can be used for removal of BOD, nitrification, and denitrification.

Attenuation: Reduction of the signal power of field strength as a function of distance through a material. Also refers to shielding effectiveness. ATP: Adenosine triphosphate. Chemical energy generated by substrate oxidations is conserved by formation of high-energy compounds such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP) or compounds containing the thioester bond.

Autoclave: Vessel for heating materials under high steam pressure. Used for sterilization and other applications. Autolysis: Spontaneous lysis.

Autoradiography: Detecting radioactivity in a sample, such as a cell or gel, by placing it in contact with a photographic film.

Autotroph: Organism which uses carbon dioxide as the sole carbon source. Autotrophic nitrification: Oxidation of ammonium to nitrate through the combined action of two chemoautotrophic organisms, one forming nitrite from ammonium and the other oxidizing nitrite to nitrate.

Autotrophy: A unique form of metabolism found only in bacteria. Inorganic compounds (e.g., NH3, N02-, S2, and Fe2+) are oxidized directly (without using sunlight) to yield energy. This metabolic mode also requires energy for C02 reduction, like photosynthesis, but no lipid-mediated processes are involved. This metabolic mode has also been called chemotrophy, chemoautotrophy, or chemolithotrophy.

AWT: Advanced Waste Treatment - any process of water renovation that upgrades treated wastewater to meet reuse requirements.

Axenic: Literally "without strangers." A system in which all biological populations are defined, such as a pure culture.

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