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Glossary of Environment and Microbiology Terms

Are you experiencing difficulty understanding the terms in various articles involving cleanup of our environment? When someone starts discussing F/M ratios and MCRTs, are you too embarrassed to ask what they are talking about? Well this glossary was designed for you.

 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

I (Back to Top of Page)

 Incineration:  The conversion of dewatered wastewater solids by combustion (burning) to ash, carbon dioxide, and water vapor.
Infiltration:  The seepage of groundwater into a sewer system, including service connections. Seepage frequently occurs through defective or cracked pipes, pipe joints, connections or manhole walls.
 Influent: The liquid - raw (untreated) or partially treated - flowing into a reservoir, basin, treatment process or treatment plant. 
Inoculate:  To introduce a seed culture into a system, such as with the addition of ALKEN CLEAR-FLO® cultures. 
Inorganic waste:  Waste material such as sand, salt, iron, calcium, and other mineral materials which are only slightly affected by the action of organisms. Inorganic wastes are chemical substances of mineral origin; whereas organic wastes are chemical substances usually of animal or plant origin. 
 Interface: The common boundary layer between two substances such as between water and a solid (metal) or between water and a gas (air) or between a liquid (water) and another liquid (oil). 
Intraspecies:  Within same species; Elk vs. Elk 
 Interspecies:  Between two different species, such as tomato and weeds.
 Ionization The process of adding electrons to, or removing electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, and nuclear radiation can cause ionization. 

K (Back to Top of Page)

 Kick net: 500 micron white mesh net is designed to meet the requirements of groups performing USEPA Rapid Bioassessment Protocols for Benthic Invertebrates. (Benthic = bottom dwelling)
 Krebs Cycle:  The oxidative process in respiration by which pyruvate (via acetyl coenzyme A) is completely decarboxylated to C02. The pathway yields 15 moles of ATP (150,000 calories).

L (Back to Top of Page)

 Lignin: A complex polymer that occurs in woody material of higher plants. It is highly resistant to chemical and enzymatic degradation. Lignin is composed of various intermolecular linkages between phenylpropanes and guaiacyl, syringyl, p-hydroxyphenyl, and biphenyl nuclei. Analysis of the metabolic pathway has shown that the dimeric lignin compounds are degraded to protocatechuate or 3OMGA (3-O-methylgallic acid) and that these compounds are cleaved by protocatechuate 4,5-dioxygenase encoded by ligAB. Among the dimeric lignin compounds, the degradation of ß-aryl ether and the biphenyl structure is the most important, because ß-aryl ether is most abundant in lignin (50%) and the biphenyl structure is so stable that its decomposition is rate-limiting in lignin degradation . Sphingomonas paucimobilis is able to degrade a wide variety of dimeric lignin compounds, including ß-aryl ether, biphenyl, and diarylpropane
 Liquefaction:  The conversion of large solid particles of sludge into very fine particles which either dissolve or remain suspended in wastewater.
 Log growth: A growth phase in which cell production is maximum. 
 Lysing:  A disintegration or breakdown of cells which releases organic matter.
 Lyophilization, Lyophilize:  Freeze-drying, (sometimes spelled incorrectly as liophilization)

M (Back to Top of Page)

 MacConkey Streak:  Laboratory test for the presence of gram negative bacteria. We use this test to detect contamination of Bacillus products such as CF 1000, 1002, 4002 and som of the Enz-Odor® products.
 Macronutrient:  An element required in large proportion by plants and other life forms for survival and growth. Macronutrients include Nitrogen (N), Potassium (K), and Phosphorous (P).
 Masking agent:  Substance used to cover up or disguise unpleasant odors. Liquid masking agents are dripped into wastewater, sprayed into the air, or evaporated (using heat) with the unpleasant fumes or odors and then discharged into the air by blowers to make an undesirable odor less noticeable.
 M: Microorganisms - small organisms which require a microscope to be seen. M represents the SS in the mixed liquor and is part of the F/M ratio. 
 MCRT: Mean Cell Retention Time - days. An expression of the average time that a microorganism will spend in an activated sludge process.
 Mechanical aeration: The use of machinery to mix air and water so that oxygen can be absorbed into the water. Some examples are paddle wheels, mixers, rotating brushes to agitate the surface of an aeration tank; pumps to create fountains; and pumps to discharge water down a series of steps forming falls or cascades.
 Media: The material in the trickling filter on which slime accumulates and organisms grow. As settled wastewater trickles over the media, organisms in the slime remove certain types of wastes thereby partially treating the wastewater. Also the material in a rotating biological contactor (RBC) or in a gravity or pressure filter.
 MEK:  Methyl ethyl ketone.
 Mercaptans:  Compounds containing sulfur which have an extremely offensive skunk-like odor. Also sometimes described as smelling like garlic or onions.
 Mesophilic bacteria:  A group of bacteria that grow and thrive in a moderate temperature range between 68 F (20 C) and 113 F (45 C).
 Metabolism:  All of the processes or chemical changes in an organism or a single cell by which food is built up (anabolism) into living protoplasm and by which protoplasm is broken down (catabolism) into simpler compounds with the exchange of energy.
 MGD: Million gallons daily - refers to the flow through a waste treatment plant.
 Mg/L: Milligrams per liter = ppm (parts per million) - expresses a measure of the concentration by weight of a substance per unit volume. 
 Micron: A unit of length. One millionth of a meter or one thousandth of a millimeter. One micron equals 0.00004 of an inch.
 Micronutrient: An element required by plants and bacteria, in proportionately smaller amounts, for survival and growth. Micronutrients include: Iron (Fe), Managanese (MN), Zinc (Zn), Boron (B), and Molybdenum (Mo).
 MIK: Methyl Isobutyl Ketone.
 Miloginite: The name coined by a resident of Milwaukee, Wisconsin for "sewage sludge", so he could scam people into buying sludge instead of paying to dispose of it! When this ingredient is listed in a septic product, you can be assured that the product is fraudulent! You don't use sludge to get rid of sludge! 
 Molecule: The smallest division of a compound that still retains or exhibits all the properties of the substance. 
Monoculture: Aquaculture in which one species is grown.
 Motile: Motile organisms exhibit or are capable of movement. 
 ML: Mixed Liquor - the combination of raw influent and returned activated sludge. (no, not mixed drinks for human consumption)
 MLSS:  Mixed Liquor Suspended Solids - the volume of suspended solids (see SS) in the mixed liquor (see ML) of an aeration tank.
 MLVSS: Mixed Liquor Volatile Suspended Solids - the volume of organic solids that can evaporate at relatively low temperatures (550 C) from the mixed liquor of an aeration tank. This volatile portion is used as a measure or indication of microorganisms present. Volatile substances can also be partially removed by air stripping.
 MPN index: Most Probable Number of coliform-group organisms per unit volume of sample water. Expressed as a density or population of organisms per 100 mL of sample water
 MRSA: Abbreviation for either Multiple Antibiotic Resistant Staph. or Methicillyn Antibiotic Resistant Staph. Alken-Murray does not use Staph. in its products and we test to verify that with QC8. We also test the strains we select with common antibiotics and refuse to use any strains that are resistant to the most commonly used antibiotics, despite other favorable traits, since we do not want to risk responsibility for passing negative traits to pathogens found in nature.
MSDS:  Material Safety Data Sheet - a document that provides pertinent information and a profile of a particular hazardous substance or mixture. An MSDS is normally developed by the manufacturer or formulator of the hazardous substance or mixture. The MSDS is required to be made available to employees and operators whenever there is the likelihood of the hazardous substance or mixture being introduced into the workplace. Some manufacturers prepare MSDS for products that are NOT considered to be hazardous to show that the product or substance is NOT hazardous.
 Mutualism: Two species living together in a relationship in which both benefit from the association. 

N (Back to Top of Page)

 NH3N: Ammonia nitrogen. (The 3 should be subscripted, but I have not figured out how to make this happen on the internet) 
 Nosocomial:  Hospital-acquired infections. Specific species are most well-known for Nosocomial transmission and rarely pass from human to human within their native environments. Since many people are taken to hospitals for physical trauma (car crash, surgery needed, etc.) or disease (including cancer, viral or bacterial infections, malfunctioning organs needing transplant), their naturally-protective immune systems may be damaged by the injury. disease or even by treatment (radiation, chemotherapy, drugs to cancel transplant resistance, etc.), improving the ability of any bacteria present to spread from patient to patient and among hospital staff, themselves. Nosocomial strains spread in hospital environments by developing incresed virulence factors, that enhance spread of infection. Whether acquired by mutatation or "horizontal gene transfer", every Nosocomial infection seeks to add antibiotic resistance genes that enable them to escape treatment with antibiotics that used to rapidly rescue hospital patients by killing them off. At this time, the most common Nosocomial bacteria belong to the following species: Serratia marcescens, Acinetobacter baumanii, Alcaligenes faecalis, Pseudomonas aeruginosa, Legionella pneumophila and the one infective strain of Escherichia coli, strain 0157. Although rarely causing serious infections, most health authorities also monitor the import and transfer of Stenotrophomonas maltophila, because this species is known for having more genes for antibiotic-resistance than any other known species and is suspected of passing along these genes via horizontal gene transfer, a terrifying prospect.
 NPDES Permit: National Pollutant Discharge Elimination System permit is the regulatory agency document issued by either a federal or state agency which is designated to control all discharges of pollutants from point sources into U.S. waterways. NPDES permits regulate discharges into navigable waters from all point sources of pollution, including industries, municipal wastewater treatment plants, sanitary landfills, large agricultural feed lots and return irrigation flows. 
 Nitrification: An aerobic process in which bacteria change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate). The second-stage BOD is sometimes referred to as the "nitrification stage" (first-stage BOD is called the "carbonaceous stage"). 
 Nitrifying bacteria:  Bacteria that change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate).
 Nitrogen fixation:  Conversion of atmospheric nitrogen into organic nitrogen compounds available to green plants; a process that can be carried out only by certain strains of soil bacteria. None of these are present in Alken Clear-Flo® formulas.
Nucleic acid:   An organic acid consisting of joined nuceleotide complexes; the principal tyes are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
 Nutrients: Substances which are required to support living plants and organisms. Major nutrients are carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorus. Nitrogen and phosphorus are difficult to remove from wastewater by conventional treatment processes because they are water soluble and tend to recycle. 

O (Back to Top of Page)

 Obligate aerobe: Bacteria which require the presense of oxygen, such as Pseudomonas flourescens. A few strains of this species are capable of utilizing nitrate to allow anaerobic respiration.
 Oil Retention Boom: A floating baffle used to contain and prevent the spread of floating oil on a water surface. 
 Organic matter: All of the degradable organics. Living material containing carbon compounds. Used as food by microorganisms. 
 Organic nitrogen: The nitrogen combined in organic molecules such as proteins, amines, and amino acids. 
 ORP: Oxidation reduction potential - the degree of completion of a chemical reaction by detecting the ratio of ions in the reduced form to those in the oxidized form as a variation in electrical potential measured by an ORP electrode assembly. 
OSHA: The Williams-Steiger Occupational Safety and Health Act of 1970 (OSHA) is a law designed to protect the health and safety of industrial workers and treatment plant operators. It regulates the design, construction, operation and maintenance of industrial plants and wastewater treatment plants. The Act does not apply directly to municipalities, EXCEPT in those states that have approved plans and have asserted jurisdiction under Section 18 of the OSHA Act. Wastewater treatment plants have come under stricter regulation in all phases of activity as a result of OSHA standards, which also refers to the federal and state agencies which administer OSHA. 
 Organic waste: Waste material which comes mainly from animal or plant sources. Organic waste generally can be consumed by bacteria and other small organisms. Inorganic wastes are chemical substances of mineral origin.
 Organism: Any form of animal or plant life. 
 Oxidation:  Combining elemental compounds with oxygen to form a new compound. A part of the metabolic reaction.
 Oxidizing bacteria:  Any substance such as oxygen (O2) and chlorine (Cl2), that can aaccept electrons. When oxygen or chlorine is added to wastewater, organic substances are oxidized. These oxidized organic substances are more stable and less likely to give off odors or to contain disease bacteria.
 Ozonation: The application of ozone to water, wastewater, or air, generally for the purposes of disinfection or odor control. 

P (Back to Top of Page)

 Parisitism: One organism living on or in another to obtain nourishment, without provviding any benefit to the host organism.
 Particulate: Free suspended solids. 
 Pathogenic organisms: Bacteria, viruses or cysts which cause disease (typhoid, cholera, dysentery) in a host (such as a person). There are many types of bacteria (non-pathogenic) which do NOT cause disease. Many beneficial bacteria are found in wastewater treatment processes actively cleaning up organic wastes. 
 PAH: Polycyclic Aromatic Hydrocarbons. (rarely, but sometimes used as the abbreviation for polyaluminum hydroxide)
 PCB: Polychlorinated biphenyls. Aka polychloro-biphenyls. Difficult to remediate chemical used in old-style transformers. Concentrated PCBs used to be referred to as "1268". 
 Percolation: The movement or flow of water through soil or rocks 
 Peristaltic pump: A type of positive displacement pump 
 pH:  pH is an expression of the intensity of the basic or acidic condition of a liquid. Mathematically, pH is the logarithm (base 10) of the reciprocal of the hydrogen ion concentration. The pH may range from 0 to 14, where 0 is most acidic, 14 most basic, and 7 is neutral. Natural waters usually have a pH between 6.5 and 8.5.
 Phenol: An organic compound that is an alcohol derivative of benzene. 
 Phototroph: A microorganism which gains energy from sunlight (radiant energy). 
 PIB: Product Information Bulletin. General information on a product. 
 Pin Floc: Excessive solids carryover. May occur from time to time as small suspended sludge particles in the supernatant. There are two kinds: grey -ashlike, inert, has low BOD - indicates old sludge; and brown, but a portion neither settles nor rises, has high BOD - indicates young sludge 
Predation:  One species benefits at the expense of another. 
 ppm: Parts Per Million - the unit commonly used to designate the concentration of a substance in a wastewater in terms of weight ie. one pound per million pounds, etc. ppm is synonymous with the more commonly used term mg/L (milligrams per liter).
 Pollution: The impairment (reduction) of water quality by agriculture, domestic or industrial wastes (including thermal and radioactive wastes) to such a degree as to hinder any beneficial use of the water or render it offensive to the senses of sight, taste, or smell or when sufficient amounts of waste creates or poses a potential threat to human health or the environment. 
 Polyculture: Fish farming in which 2 or more compatible or symbiotic species of fish are grown together. Also known as Multiculture. 
Polymer:  A chemical formed by the union of many monomers (a molecule of low molecular weight). Polymers are used with other chemical coagulants to aid in binding small suspended particles to form larger chemical flocs for easier removal from water. All polyelectrolytes are polymers, but not all polymers are polyelectrolytes. 
 Potable water. Water that does not contain objectionable pollution, contamination, minerals, or infective agents and is considered satisfactory for drinking.
 POTW: Publicly Owned Treatment Works, as opposed to an industrially owned facility or pipe system.
 Preliminary treatment: The removal of metal, rocks, rags, sand, eggshells, and similar materials which may hinder the operation of a treatment plant. Preliminary treatment is accomplished by using equipment such as racks, bar screens, comminutors, and grit removal systems. 
 Pretreatment facility: Industrial wastewater treatment plant consisting of one or more treatment devices designed to remove sufficient pollutants from wastewaters to allow an industry to comply with effluent limits established by the US EPA General and Categorical Pretreatment Regulations or locally derived prohibited discharge requirements and local effluent limits. Compliance with effluent limits allows for a legal discharge to a POTW. 
 Primary treatment: A wastewater treatment process that takes place in a rectangular or circular tank and allows those substances in wastewater that readily settle or float to be separated from the water being treated. 
 Probiotic A commercial product containing selected strains of natural commensal species of bacteria, known to thrive in the acid pH of the digestive system, while producing valuable food-digesting enzymes, without causing any harm to the host organism. Such products often contain "prebiotic" nutrients, compounds which selectively encourage growth of the included beneficial bacteria, enhancing their ability to "out-compete" undesirable organisms, including pathogenic (disease-causing) species.
 Procaryote:  Microorganisms which do NOT have an organized nucleus surrounded by a nuclear membrane. Bacteria and Archaea stand alone in this primitive kingdom. Plants, fungi, animals, birds, fish and all other organisms fit into the kingdom of "Eucaryotes".
 Protozoa:  A group of motile microscopic animals (usually single-celled and aerobic) that sometimes cluster into colonies and often consume bacteria as an energy source.
 Psychrophilic bacteria: Bacteria whose optimum temperature range is between 0 and 20 C (32 to 68 C), such as those found in Alken Clear-Flo® 7018. 
 Putrefaction: Biological decomposition of organic matter with the production of ill-smelling products associated with anaerobic conditions. 

R (Back to Top of Page)

 Rack: Evenly spaced parallel metal bars or rods located in the influent channel to remove rags, rocks, and cans from wastewater. 
 RAS: Return activated sludge - settled activated sludge that is collected in the secondary clarifier and returned to the aeration basin to mix with incoming raw settled wastewater. 
 RASVSS: Return Activated Sludge Volatile Suspended Solids. 
 RBC: Rotating biological contactor - an attached culture wastewater treatment system
 Reagent: A pure chemical substance that is used to make new products or is used in chemical tests to measure, detect, or examine other substances. 
 Recycle: The use of water or wastewater within (internally) a facility before it is discharged to a treatment system.
REDOX: Biological reductions/oxidations. These reactions usually require enzymes to mediate the electron transfer. The sediment in the bottom of a lake, sludge in a sewerage works or septic tank will have a very low redox potential and will likely be devoid of any oxygen. This sludge or waste water will have a very high concentration of reductive anaerobic bacteria, indeed the bulk of the organic matter may in fact be bacteria. As the concentration of oxygen increases the oxidation potential of the water will increase. A low redox potential or small amount of oxygen is toxic to anaerobic bacteria, therefore as the concentration of oxygen and redox potential increases the bacterial population changes from reductive anaerobic bacteria to oxidative aerobic bacteria. Measurement of REDOX potential is also referred to as ORP. 
 Reducing agent: Any substance, such as the base metal (iron) or the sulfide ion that will readily donate (give up) electrons. The opposite of an oxidizing agent. 
 Refractory materials: Material difficult to remove entirely from wastewater such as nutrients, color, taste, and odor-producing substances and some toxic materials. 
 Respiration: The energy producing process of breathing, by which an organism supplies its cells with oxygen and relieves itself of carbon dioxide. A type of heterotrophic metabolism that uses oxygen in which 38 moles of ATP are derived from the oxidation of 1 mole of glucose, yielding 380,000 cal. (An additional 308,000 cal is lost as heat.)
 Rhizosphere: Soil surrounding plant roots. 
 R/O unit: Reverse Osmosis Unit for water purification in small aquariums and miniature yard-ponds, utilizes a membrane under pressure to filter dissolved solids and pollutants from the water. Two different filter membranes can be used: the CTA (cellulose triacetate) membrane is less expensive, but only works with chlorinated water and removes 50-70% of nitrates, and the TFC membrane, which is more expensive, removes 95% of nitrates, but is ruined by chlorine. R/O wastes water and a system that cleans 100 gallons a day will cost from $400 to $600 with membrane replacement adding to the cost. A unit that handles 140 gallons a day will cost above $700.00.  
 RR: Respiration rate - the weight of oxygen utilized by the total weight of MLSS in a given time. 
Runoff:  Water running down slopes rather than sinking in (again,result of poor humus content) Ex. erosion due to deforestation 

S (Back to Top of Page)

 Saprophytic: Bacteria that breakdown bodies of dead plants and animals (non-living organic material), returning organic materials to the food chain. Saprophytic bacteria are usually non-pathogenic, too. Most Alken Clear-Flo® products are saprophytic. 
 SAR: Sodium Adsorption Ratio - this ratio expresses the relative activity of sodium ions in the exchange reactions with the soil. 
 SCFM: Cubic feet of air per minute at standard conditions of temperature, pressure and humidity (0 , 14.7 psi and 50% relative humidity). 
 Secondary Treatment: A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually the process follows primary treatment by sedimentation. The process commonly is a type of biological treatment process followed by secondary clarifiers that allow the solids to settle out from the water being treated. 
 Sedimentation: The process of subsidence and deposition of suspended matter from a wastewater by gravity. 
 Seeding:  Introduction of microorganisms (such as ALKEN CLEAR-FLO® 1000 series for aquaculture, 4000 series for grease, and 7000 series for industrial and municipal wastewater) into a biological oxidation unit to minimize the time required to build a biological sludge. Also referred to as inoculation with cultured organisms.
Seine net:  A net designed to collect aquatic organisms inhabiting natural waters from the shoreline to 3' depths is called a seine net. Most often a plankton seine. 
 Septic: A condition produced by anaerobic bacteria. If severe, the wastewater turns black, gives off foul odors, contains little or no dissolved oxygen and creates a high oxygen demand. 
 Septicity: Septicity is the condition in which organic matter decomposes to form foul-smelling products associated with the absence of free oxygen. If severe, the wastewater turns black, gives off foul-odors, contains little or no dissolved oxygen and creates a heavy oxygen demand. 
 Septic Tank: Untreated liquid household wastes (sewage) will quickly clog your absorption field if not properly treated. The septic tank is a holding tank in which this treatment can take place. When sewage enters the septic tank, the heavy solids settle to the bottom of the tank; the lighter solids, fats and greases partially decompose and rise to the surface and form a layer of scum. The solids that have settled to the bottom are attacked by bacteria and form sludge.
 Settleable solids: Those solids in suspension which will pass through a 2000 micron sieve and settle in one hour under the influence of gravity. 
 Sewage: The used water and water-carried solids from homes that flow in sewers to a wastewater treatment plant. The preferred term is wastewater. 
 Shock load: The arrival at a plant of a waste which is toxic to organisms in sufficient quantity or strength to cause operating problems. Possible problems include odors and sloughing off of the growth or slime on a trickling-filter media. Organic or hydraulic overloads also can cause a shock load. 
 Sloughings: Trickling-filter slimes that have been washed off the filter media. They are generally quite high in BOD and will lower effluent quality unless removed. 
 Sludge: The settleable solids separated from liquids during processing; the deposits of foreign materials on the bottoms of streams or other bodies of water. 
 Sludge age: A measure of the length of time a particle of suspended solids has been retained in the activated sludge process.
 Slugs: Intermittent releases or discharges of industrial wastes. 
 Soluble: Matter or compounds capable of dissolving into a solution. 
 Soluble BOD: Soluble BOD is the BOD of water that has been filtered in the standard suspended solids test. 
 Solution: A liquid mixture of dissolved substances, displaying no phase separation. 
 Specific gravity: Weight of a particle, substance or chemical solution in relation to an equal volume of water. 
 Spec. Sheet: Specification Sheet. Detailed information of a product including, tests, color, odor, specific gravity, bacterial strains, other major ingredients, etc. 
 SS: Suspended solids - Solids in suspension in water which can be filtered out on a lab filter. 
 Stabilize: To convert to a form that resists change. Organic material is stabilized by bacteria which convert the material to gases and other relatively inert substances. Stabilized organic material generally will not give off obnoxious odors. 
 Stasis: Stagnation or inactivity of the life processes within organisms. 
 Sterilization: The removal or destruction of all living microorganisms, including pathogenic and other bacteria, vegetative forms and spores. 
 Storm sewer:  A separate pipe, conduit or open channel (sewer) that carries runoff from storms, surface drainage and street wash, but does not include domestic and industrial wastes. Storm sewers are often the recipients of hazardous or toxic substances due to the illegal dumping or hazardous wastes or spills created by accidents involving vehicles and trains transporting these substances.
 STP test:  Laboratory test for nitrifiers. For CF1100, 7110 & 1400 to be within specifications, this test must show a positive color change result (from fuschia to yellow) within 7 days. When testing the 50X concentrate of these three products, a positive color change is expected within 24 hours.
 STP: Standard Temperature (25 C) and Pressure (300 mm Mercury). 
 Substrate: The base on which an organism lives. The soil is the substrate of most seed plants where rocks, soil, water, or other tissues are substrates for other organisms. 

Liquid removed from a tank once the solids have settled. When hydrating Alken Clear-Flo formulas, the supernatant is the bran-free liquid which can then be applied by sprayer, without clogging the sprayer.

Supernatant commonly refers to the liquid between the sludge on the bottom and the scum on the surface of an anaerobic digester. This liquid is usually returned to the influent wet well or to the primary clarifier. 

 Surfactant: Surface-active agent. The active agent in detergents that possesses a high cleaning ability. Used in a spray solution to improve its sticking and wetting properties when applied to plants, algae, or petroleum. 
 Synergistic:  When two or more organisms coexist in a relationship that is strongly co-operative, so that their combined effect exceeds a simple sum of their individual effects.
 Synthesis: Breaking down organic compounds and converting the degradation products into new cell growth. An energy using process.  
 SV: Sludge volume - a settling test using a two liter settleometer to measure sludge quality expressed in percent and related to time, ie. 80% in five minutes or 30% in 30 minutes. Also used to determine the rate of settling. 
 SVI:  Sludge volume index - a settling test used to measure sludge quality.
 SVR: The volume of sludge blanket divided by the daily volume of sludge pumped from the thickener. 
 SV30:  The value obtained in a 30 minute settleometer test.

T (Back to Top of Page)

 Taxonomy: The classification, nomenclature, and laboratory identification of organisms (Do not confuse with taxidermy - stuffing dead animals) 
 TDS: Total Dissolved Solids is commonly estimated from the electrical conductivity of the water. Pure water is a poor conductor of electricity. Impurities dissolved in the water cause an increase in the ability of the water to conduct electricity. Conductivity, usually expressed in units of microsimens, formerly micromhos or in mg/l, thus becomes an indirect measure of the level of impurities in the water. 
 Thermophilic bacteria: Hot temperature bacteria. a group of bacteria that grow and thrive in temperatures above 113 F (45 C), such as Bacillus licheniformis. The optimum temperature range for these bacteria in anaerobic decomposition is 120 F (49 C) to 135 F (57 C). 
 TOC: Total organic carbon - a measure of the amount of organic carbon in water.
 TOD:  Another method of measuring organic matter in wastewater involves the oxidation of the sample to stable end products in a platinum-catalyzed combustion chamber at 900 degrees C. Total oxygen demand is determined by measuring the oxygen content of the inert carrier gas, nitrogen. TOD measurements are becoming more popular because of their quickness in determining what is entering the plant and how the plant is responding. Analysis time is approximately 5 minutes. The results obtained generally will be equivalent to those obtained in the COD test.
 Toxic: A substance which is poisonous to a living organism.
 Toxicity: The relative degree of being poisonous or toxic. A condition which may exist in wastes and will inhibit or destroy the growth or function of certain organisms. 
 Transpiration: The process by which water vapor is released to the atmosphere by living plants, a process similar to people sweating. 
 Trickling filter:  An attached culture wastewater treatment system. A large tank generally filled with rock or rings (see Bio-Tower). Wastewater is sprayed over the top of the media, providing the opportunity for the formation of slimes or biomass to remove wastes from the wastewater, through revolving arms which have spray nozzles. Water is pumped from the bottom of a trickle filter to a secondary clarifier.
 TSS: Total suspended solids. 
 Turbidity: The amount of suspended matter in wastewater, obtained by measuring its light scattering ability. 

U (Back to Top of Page)

 Unicellular: Single celled organism, such as bacteria. 
 Upset: An upset digester does not decompose organic matter properly. The digester is characterized by low gas production, high volatile acid/alkalinity relationship, and poor liquid-solids separation. A digester in an upset condition is sometimes called a "sour" or "stuck" digester. 

V (Back to Top of Page)

 Vector: An insect or other organism capable of transmitting germs or other agents of disease.
 Vegetative: Actually growing state. 
 Volatile:  A volatile substance is one that is capable of being evaporated or changed to a vapor at a relatively low temperature. Volatile substances also can be partially removed by air stripping.
 VS/L: Measure of volatile solids, usually expressed as g VS/L/day = grams volatile solids per liter per day. 

W (Back to Top of Page)

 WAS: Waste activated sludge, mg/L. The excess growth of microorganisms which must be removed from the process to keep the biological system in balance. 
 Wastewater: The used water and solids from a community that flow to a treatment plant. Storm water, surface water, and groundwater infiltration also may be included in the wastewater that enters a wastewater treatment plant. The term "sewage" usually refers to household wastes, but this word is being replaced by the term "wastewater". 
 Weir: A wall or plate placed in an open channel and used to measure the flow of water. 

Z (Back to Top of Page)

 Zoogleal film: A complex population of organisms that form a "slime growth" on a trickling-filter media and break down the organic matter in wastewater.
 Zoogleal mass:  Jelly-like masses of bacteria found in both the trickling filter and activated sludge processes.

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