The Complete Activated Sludge Glossary
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Filament Type numbers
0041 See Type 0041. 0092 See Type 0092. 021N See Type 021N. 0411 See Type 0411. 0581 See Type 0581. 0675 See Type 0675. 0803 See Type 0803. 0914 See Type 0914. 0961 See Type 0961. 1701 See Type 1701. 1702 See Type 1702. 1851 See Type 1851.1852 See Type 1852. 1863 See Type 1863.
2 stage Bardenpho process.
A biological phosphorus removal process which consists of 2 reactors providing the requisite anaerobic/aerobic cycling. The process is designed to operate at sludge ages lower than the minimum for nitrification and consequently avoids the problems of nitrate return to the anaerobic zone. Plants using this process often use a separate nitrification process (biofilm/trickling filter). The A/O (anaerobic/oxic) process has a similar process layout.
3 stage Phoredox Process
A biological 3 stage or zone process developed from the original 5 stage or modified Bardenpho process. The 3 stage Phoredox Process removes carbon, nitrogen and phosphorus in a process using 3 reaction zones. The 3 reaction zones consist of an anaerobic zone, anoxic zone and aerobic zone followed by secondary clarification. Recycles from the clarifier to the anaerobic zone at the head of the plant (return sludge or 's'-recycle) and a mixed liquor denitrification or 'a'-recycle from the aerobic zone to the anoxic zone.
This simplified plant was first proposed and trialed in the 1970's and is essentially a MLE plant with an anaerobic zone. This plant is the basis of most subsequent biological nitrogen and phosphorus removal plants. Various feed variations and process modifications have been developed to overcome process limitations due to nitrate return to the anaerobic zone. See Modified Bardenpho Process, University of Cape Town Process, Modified University of Cape Town Process and Johannesburg Process
5 stage Phoredox Process See Modified Bardenpho Process.
16S rRNA
A large polynucleotide (~1500 bases) that functions as a part of the small subunit of the ribosome of prokaryotes (Bacteria and Archaea) and from whose sequence evolutionary relationships can be obtained; eukaryotic counterpart, 18S rRNA.
Absorption
The taking in or soaking up of one substance into the body of another by molecular or chemical action.
Acclimatization
The physiological and behavioral adjustments of an organism to changes in its environment.
Acetogenic bacterium
Prokaryotic organism that uses carbonate as a terminal electron acceptor and produces acetic acid as a waste product.
Acid
Any substance capable of giving up a proton; a substance that ionizes in solution to give the positive ion of the solvent; a solution with a pH measurement less than 7.
Acidity
The quantitative capacity of aqueous solutions to react with hydroxyl ions. It is measured by titration with a standard solution of base to a specified end point
Acid fastness
A staining property of Mycobacterium species where cells stained with hot carbolfuschin do not decolorize with acid-alcohol.
Acidophile
Organism that grows best at acidic pH values.
Acidotrophic bacteria
Bacteria which are able to flourish in very acidic (pH <3.5) conditions. Many are aerobic and function over relatively narrow pH ranges.
acre-foot (acre-ft)
The volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic meters.
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 primary tanks APTs
APTs produce VFAs by allowing a sludge blanket to form in the primary clarifier. Fermentation and VFA production then take place in this sludge blanket.
Activated Sludge Process
A biological treatment process in which a mixture of sewage and activated sludge is agitated and aerated. The activated sludge is subsequently separated from the treated sewage by settlement and may be re-used. A common method of disposing of pollutants in wastewaters.
In the process, large quantities of air are bubbled through wastewaters that contain dissolved organic substances in open aeration tanks. Oxygen is required by bacteria and other types of microorganisms present in the system to live, grow, and multiply in order to consume the dissolved organic "food", or pollutants in the waste. After several hours in a large holding tank, the water is separated from the sludge of bacteria and discharged from the system. Most of the activated sludge is returned to the treatment process, while-the remainder is disposed of by one of several accepted methods.
Adaptability
The ability of microorganisms either as individual strains, or as a consortium of strains, to adapt to function in some way within a given environment. Often there is a lag (induction) time before this activity commences.
Adsorption
A surface phenomena in which a solute (soluble material) concentrates or collects at a surface (the adsorbent).
Advanced Treatment
A level of wastewater treatment more stringent than secondary treatment; requires an 85-percent reduction in conventional pollutant concentration or a significant reduction in nonconventional pollutants.
Advanced Wastewater Treatment
Any treatment of sewage that goes beyond the secondary or biological water treatment stage and includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids. (See primary, secondary treatment).
Aeration
The act of mixing a liquid with air (oxygen). Intimate contact of the atmosphere and water to add air (oxygen) to the water. The term is also applied to gas stripping where an undesirable gas is removed from the water.
Aeration basin.
The aeration basin is the aerobic reactor where the treatment process occurs. This is the same as an aeration tank, aeration zone, or aerobic reactor (basin, zone etc).
Aeration tank
A tank in which wastewater or other liquid is aerated. See biological reactor.
Aerator
A device that brings air and a liquid into intimate contact. See diffuser.
Aerobe
An organism that grows in the presence of oxygen; (requires oxygen as an electron acceptor) may be facultative, obligate, or microaerobic.
Aerobic
Aerobic reaction conditions require that O2 is present in solution. Under aerobic conditions, the bacteria generate energy from the organic substrate by oxidising it. The O2 acts as an electron acceptor in this oxidation-redaction reaction.
(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.
Aerobic action
A biological process promoted by action of bacteria in the presence of dissolved oxygen.
Aerosol
Suspension of particles in airborne water droplets.
Aerotolerant
Of an anaerobe, not being inhibited by O2.
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.
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
Aggressivity
The state in which an organism is active in its environment and able to compete with other strains for space, nutrients, water and gases.
Air sparging
A technology that injects air into the lower of two
horizontal wells. Contaminants are forced into the uppermost well where they areremoved. Especially effective in difficult to reach areas such as beneath buildings, ponds, or lagoons. Also called vapor extraction.
Air stripping
A technology that involves the mass transfer of volatile contaminants from water to air. Typically conducted in a packed tower or aeration tank, a spray nozzle distributes contaminated water over packing in a column; a fan forces air against the water flow; and a sump at the bottom of the tower collects the decontaminated water.
Alcohol
An organic compound with one or more hydroxyl "-OH" groups.e.g. ethanol (ethyl alcohol CH3-CH2-OH) or methanol (methyl alcohol CH3-OH).
Aldehyde
An organic compound with a carbonyl group (-CHO) at one end of a hydrocarbon group. e.g. CH3-CHO (acetaldehyde or ethanal).
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.
Algal Bloom
An unusually large concentration of algae (microscopic, aquatic plants), made up of one or more species.
Aliphatic
Organic compound in which the main carbon structure is a straight chain.
Alkali
Typically, any substance that has highly basic properties; used particularly with reference to the soluble salts of sodium, potassium, calcium, and magnesium.
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 (CaCO3) and Slaked or builders lime (Ca(OH)2) is the most commonly used alkaline material in wastewater treatment.
Alkalinity
The degree of buffering available in a water is measured by its total alkalinity. In simple terms, total alkalinity is the mass of strong acid required to convert the carbonate and bicarbonate ions to carbonic acid. Alkalinity is expressed in terms of equivalent CaCO3 (mg CaCO3/l).
Alkaliphile, alkalophile
An organism that grows best at high pH.
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.
Alum (Potash Alum)
Astringent crystalline double sulfate of an alkali. K2SO4Al2(SO4)3.24 H2O. Used in the precipitation of phosphorus and as a flocking agent. Excess aluminum in the environment can be hazardous.
Ambient
Typically refers to the prevailing dynamic environmental conditions in a given area.
Ameboid movement
A type of motility in which cytoplas-mic streaming moves the organism forward.
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.
Amine
Derivatives of ammonia in which one or more hydrogen atoms have been replaced by an organic radical, sometimes called nitrogen bases.
Amine/amino group
A functional group consisting of "-NH2".
Amino Acid
A chemical compound which consists of a carbon chain with the acidic carboxylic acid group, "-COOH" and the alkaline amine group, "-NH2." These compounds are the precursors or building blocks for proteins which are polymers of amino acids linked via the acid and alkaline groups. Amino acids have the general structure R-CH-(NH)2-COOH where the "R" group may be one of a number of side chains, e.g. R = H . . . Glycine, R = CH3 . . . Alanine etc.
Ammonia (NH3), ammonium (NH4+)
Dissolved degradation products of urea and proteins in raw wastewater. Typically, raw wastewater contains 30 to 50 mg/L of NH3. Reactions between chlorine and ammonia are important in disinfection.
Ammonia nitrogen (NH3-N)
Elemental nitrogen present in the form of ammonia (NH3).
Ammonification
Liberation of ammonium (ammonia) from organic nitrogenous compounds by the action of microorganisms. Bacterial decomposition of organic nitrogen to ammonia.
Amoeba (plural, amoebae)
Protozoa that can alter their cell shape, usually by the extrusion of one or more pseudopodia.
Anabolism
The biochemical processes involved in the synthesis of cell constituents from simpler molecules, usually requiring energy otherwise termed Biosynthesis.
Anaerobe
An organism that grows in the absence of oxygen; some find oxygen so toxic that they may even be killed by O2.
Anaerobic respiration
Use of an electron acceptor other than O2 in an electron transport-based oxidation and leading to a proton motive force.
Anaerobic
Anaerobic reaction conditions require that no O2, NO3- and NO2- is present in solution to act as electron acceptors.
(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 action
A biological process promoted by the action of bacteria in the absence of dissolved oxygen.
Anaerobic biological treatment
Any waste treatment process utilizing anaerobic or facultative organisms in the absence of air to reduce the organic matter in water.
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.
Anaerobic waste treatment (sludge processing)
Waste stabilization brought about through the action of microorganisms in the absence of air or elemental oxygen.
Anhydrous
Chemically, without water. In common terminology, very dry.
Anhydrous ammonia (NH3)
Water-soluble colorless gas composed of molecules containing one nitrogen atom and three hydrogen atoms. Typically, ammonia is detectable because of its characteristic pungent and irritating odor. Not to be confused with aqueous ammonia, which is a 15 to 30 percent solution of ammonia in water.
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.
Anoxic
Microbiologically, anoxic is used to indicate the absence of oxygen. Usually used in reference to a microbial habitat. When used in describing wastewatewer treatment anoxic reaction conditions mean that no oxygen is present in solution, but nitrite or nitrate is available. Nitrate and nitrite act as electron acceptors for the oxidation of the organic substrate. During this reaction, they are reduced to nitrogen gas and water.
Anoxygenic photosynthesis
Use of light energy to synthesize ATP by cyclic photophosphorylation without O2 production.
Antagonism
Detrimental interaction between two entities. See synergism.
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
A chemical agent produced by one organism that is harmful to other organisms. Organic substance produced by one species of organism that in low concentrations will kill or inhibit growth of certain other organisms.
Antibiotic resistance
The acquired ability of a microor-ganism to grow in the presence of an antibiotic to which the microorganism is usually sensitive.
Antifoam agent
A material having low compatibility with foam and a low surface tension.
Antimicrobial
Harmful to microorganisms by either killing or inhibiting growth.
Antimicrobial agent
A chemical that kills or inhibits the growth of microorganisms.
Antiseptic
An agent that kills or inhibits microbial growth but is not harmful to human tissue.
Antiserum
A serum containing antibodies.
Antitoxin
An antibody that specifically interacts with and neutralizes a toxin.
A2/O Process
A three stage activated sludge process (anaerobic/anoxic/oxic) and so is essentially a variant of the 3 stage Phoredox Process.
A/O Process
See the 2 stage Bardenpho process.
Archaea
A phylogenetic domain of prokaryotes consisting of the methanogens, most extreme halophiles and hyper-thermophiles, and Thermoplusma.
Archaebacteria
A group of bacteria which evolved very early on the in the evolution of the planet. These bacteria are now found populating some of the extreme environments (eg, highly saline, sulfur-rich, methane generating and high temperatures). Older term for the Archaea.
Aromatic
A form of bonding in which ring compounds share electrons over more than two atoms. The electrons are delocalized. This leads to unusual ring stability. Benzene, toluene and xylene are all aromatic compounds. Organic compounds which contain a benzene ring, or a ring with similar chemical characteristics .
Aseptic
Free from living bacteria or other organisms.
Aseptic technique
Manipulation of sterile instruments or culture media in such a way as to maintain sterility.
Assessment
A determination of a project?s condition made by reviewing cost, schedule, technical issues, and performance against objectives, regulatory requirements, and baseline project plans.
Assimilate
To take in, absorb or consume.
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.
ATP
Adenosine triphosphate, the principal energy carrier of the cell. 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.
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.
Attached Growth Reactor
A reactor in which the microorganisms are attached to engineered surfaces within the reactor. Examples of attached growth reactors are the trickling filter and the rotating biological contactor.
Attachment
The act of a bacteria or a biocolloid becoming fixed to a surface. Growth may then follow leading to the formation of biofilms.
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 able to utilize CO2 or other inorganic carbon compounds as a sole source of carbon. Microorganisms that obtain their carbon and energy for growth from inorganic compounds. Most autotrophic bacteria are photosynthetic and use light as a source of energy to assemble the organic molecules they require. Some autotrophic bacteria carry out chemosynthesis, making organic molecules by using energy derived from the oxidation of inorganic compounds in the environment.
Autotrophy
A unique form of metabolism found only in bacteria. Inorganic compounds (e.g., NH3, NO2-, S-2, and Fe+2) are oxidized directly (without using sunlight) to yield energy. This metabolic mode also requires energy for CO2 reduction, like photosynthesis, but no lipid-mediated processes are involved. This metabolic mode has also been called chemotrophy, chemoautotrophy, or chemolithotrophy.
Auxotroph
An organism that has developed a nutritional requirement through mutation. Contrast with a Prototroph.
Average
An arithmetic mean obtained by adding quantities and dividing the sum by the number of quantities.
Average daily flow
The total flow past a point over a period of time divided by the number of days in that period.
Average dry weather flow (ADWF)
The volume of flow sewage produced on a typical day in dry weather usually measured in megalitres per day.
Axenic
Literally meaning "without strangers." A system in which all biological populations are defined, such as a pure culture, i.e. containing organisms of one type.
BACT-Best Available Control Technology
An emission limitation based on the maximum degree of emission reduction which (considering energy, environmental, and economic impacts, and other costs) is achievable through application of production processes and available methods, systems, and techniques.
Bacteria
Single-celled microorganisms in the order of 1 micron in size. All prokaryotes that are not members of the domain Archaea. A group of globally distributed, rigid, essentially unicellular microscopic organisms lacking chlorophyll. They perform a variety of biological treatment processes including biological oxidation, sludge digestion, nitrification, and denitrification.
Bacterial analysis
The examination of water and wastewater to determine the presence, number, and identity of bacteria; more commonly called bacterial examination. See bacteriological count.
Bacterial Photosynthesis
A light-dependent, anaerobic mode of metabolism. Carbon dioxide is reduced to glucose, which is used for both biosynthesis and energy production. Depending on the hydrogen source used to reduce CO2, both photolithotrophic and photoorganotrophic reactions exist in bacteria.
Bacterial slime
A polysaccharide slime that is produced by many types of bacteria. This slime helps to hold activated sludge floc together.
Bacteriological count
A means for quantifying numbers of organisms. See most probable number.
Bacteriocidal
Capable of killing bacteria.
Bacteriocins
Agents produced by certain bacteria that inhibit or kill closely related species.
Bacteriophage
A virus that infects prokaryotic cells and multiplies within the cells. Usually a bacteriophage can only infect a limited range of bacterial strains.
Bacteriostatic
Capable of inhibiting bacterial growth with-out killing.
Baffles
Deflector vanes, guides, grids, gratings, or similar devices constructed or placed in flowing water, wastewater, or slurry systems as a check or to produce a more uniform distribution of velocities; absorb energy; divert, guide, or agitate the liquids; and check eddies.
Bar Screen
In wastewater treatment, a device used to remove large solids.
Bardenpho Process
A nitrogen removal process developed in the 1970's by James Barnard. The process is essentially an MLE process with a post denitrification zone and flash aerator. The process has the potential to completely denitrify wastewaters with a low enough TKN/COD ratio although the secondary (endogenous) denitrification is slow. The use of this process layout with external carbon substrate addition (methanol) can achieve very efficient nitrogen removal with a wide range of wastewaterTKN/COD ratios.
Base
A substance which dissociates (ionizes) in aqueous solution to yield hydroxyl ions, or one containing hydroxyl ions (OH-) which reacts with an acid to form a salt or which may react with metal to form a precipitate.
Base composition
In reference to nucleic acids, the proportion of the total bases consisting of guanine plus cytosine or thymine plus adenine base pairs. Usually expressed as a guanine + cytosine (G + C) value for example, 60% G + C.
Batch culture
A closed-system microbial culture of fixed volume.
Batch Process
A treatment process in which a tank or reactor is filled, the wastewater (or solution) is treated or a chemical solution is prepared and the tank is emptied. The tank may then be filled and the process repeated. Batch treatment processes reactors are often termed Sequencing Batch reactors.
Beggiatoa
A filament rarely seen in plants, and usually only in low numbers. Its large size, refractive intracellular sulphur particles and rapid gliding motility make it easy to recognize. It is reported to be associated with septicity.
Bench-scale testing
Chemical or physical testing of equipment or processes in a laboratory conducted before large- or pilot-scale testing or prototype use.
Best management practices (BMPs)
Practices that have been developed to prevent or minimise pollution and to protect the environment. They are often applied to non-point sources of pollution where there is a need to define a range of practices that need to be applied to prevent degradation of the environment. These practices may be promoted by means of guidelines or codes of practice.
Bicarbonate alkalinity
Alkalinity caused by bicarbonate ions.
Binary Fission
During binary fission, a single cell divides transversely to form two new cells called daughter cells. Both daughter cells contain an exact copy of the genetic information contained in the parent cell.
Bioaccumulation/Biomagnification
A process where chemicals are retained in body tissue and increase in concentration over time. Biomagnification is the increase of tissue accumulation in species higher in the natural food chain as contaminated food species are eaten.
Bioaccumulator
A biological entity which is able to accumulate (either actively for degradation, or passively) chemicals within the surface coatings of EPS or within the cells themselves.
Bioamplifier
Organisms which is able to catalyze a particular physical and/or chemical event causing the event to occur at an accelerated rate.
Bioaugmentation
The addition to the environment of microorganisms that can metabolize and grow on specific organic compounds.
Bioavailability
The availability of chemicals to potentially biodegradative microorganisms.
Bioassay
Using living organisms to measure the effect of a substance, factor, or condition by comparing before-and-after data. Term is often used to mean cancer bioassays but can and is applied to other fields.
Biochemical Oxygen Demand (BOD)
A measure of the oxygen required to break down organic materials in water using biological means. The amount of oxygen required to oxidize any organic matter present in a water during a specified period of time, usually 5 days. It is an indirect measure of the amount of organic matter present in a water. Used to monitor natural waters and processed effluents discharged into natural waters.
This procedure is considered unsuitable for the monitoring of raw sewage. The BOD5 test procedure measures the rate of oxygen use under controlled conditions of time and temperature. Standard test conditions include dark incubation at 20°C for a specified time (usually 5 days). In some countries the BOD test is carried out over differing periods such as 7 days (BOD7), and 10 days (BOD10)
Biochemical oxygen demand load
The biochemical oxygen demand content, typically expressed in kilograms or pounds per unit of time, of wastewater passing into a treatment system or water body.
Biocolloid
A buoyant particle which is composed mostly of water bound together by EPS and populated by some microorganisms. Sizes may range from 6 to 100 microns or more in diameter. These suspended particles are also found to be able to act as bioaccumulators.
Biodegradable
Substance capable of being decomposed by biological processes.
Biodegradation
The breakdown of organic materials by microorganisms in soils, bodies of water, and wastewater treatment systems.
Biodetector
An instrument, device or mechanism by which the presence of biological activity can be determined.
Biodiversity
The number and variety of different organisms in the ecological complexes in which they naturally occur. Organisms are organized at many levels, ranging from complete ecosystems to the biochemical structures that are the molecular basis of heredity. Thus, the term encompasses different ecosystems, species, and genes that must be present for a healthy environment. A large number of species must characterize the food chain, representing multiple predator-prey relationships.
Biofilm
Microbial colonies encased in an adhesive, usually polysaccharide material, and attached to a surface. A film of microorganisms attached to a surface, such as that on a trickling filter, rotating biological contactor, or rocks in natural streams. A slime layer which naturally develops when bacteria attach to an inert support that is made of a material such as stone, metal, or wood.
There are also non-filamentous bacteria that will produce an extracellular polysaccharide that acts as a natural glue to immobilize the cells. In nature, nonfilament-forming microorganisms will stick to the biofilm surface, locating within an area of the biofilm that provides an optimal growth environment (i.e., pH, dissolved oxygen, nutrients). Since nutrients tend to concentrate on solid surfaces, a microorganism saves energy through cell adhesion to a solid surface rather than by growing unattached and obtaining nutrients randomly from the medium. Pseudomonas and Nitrosomonas strains are especially well known for their ability to form a strong biofilm.
Bioflocculation
The clumping together of fine, dispersed organic particles by the action of certain bacteria and microrganisms.
Biofouling
Any deleterious event in which a definable biological activity causes a deterioration in and engineered or natural process or system. Deleterious effects range from clogging, corrosion, and plugging to gas production and bioaccumulation.
Biological denitrification
The transformation of nitrate nitrogen to inert nitrogen gas by microorganisms in an anoxic environment in the presence of an electron donor.
Biological floc
A very fine, fluffy mass formed by the aggregation of fine suspended particles, as in a precipitate formed by biological activity.
Biological nutrient removal (BNR)
An adaptation of the conventional activated-sludge process where anaerobic and anoxic zones are added to biological reactors to create the correct conditions under which bacteria and other microorganisms are able to remove nitrogen and phosphorous from wastewater.
Biological Oxidation
The process by which bacteria and other types of micro-organisms consume dissolved oxygen and organic substances in waste water, using the energy released to convert organic carbon into carbon dioxide and cellular material.
Biological process
(1) The metabolic activities of bacteria and other microorganisms, as in during the breakdown of complex organic materials into simple, more stable substances during sludge digestion and secondary wastewater treatment.
(2) Any chemical process involving living organisms and their life activities. Also called biochemical process.
Biological reactors
In wastewater treatment, the tanks where aerobic, anaerobic, or anoxic conditions are created to produce healthy mixed liquor and facilitate biological treatment processes.
Biomass
A mass or clump of living organisms feeding on the wastes in wastewater, dead organisms and other debris.
Bioreactor
A facility which uses microorganisms to degrade water-based contaminants.
Bioremediation
The process of using microorganisms to degrade or break down hazardous material.
Biosensor
A device or methodology which utilises the shift in a targeted signal (commonly electro-magnetic) to quantify a biological activity or presence.
Biosolids
The semi-solid end product of wastewater treatment. Organic solid product suitable for beneficial use resulting from processing the sludge produced by sewage treatment processes.
Biostimulation
A process that increases activity of microorganisms biodegrading contaminants. For example, addition of nutrients, oxygen, or other electron donors and acceptors.
Biosynthesis
The production of needed cellular constituents from other (usually simpler) molecules See Anabolism.
Biota
The sum total of the living organisms of any designated area.
Biotransformation
Alteration of the structure of a compound by a living organism or enzyme.
Bioventing
The process of supplying oxygen in situ to oxygen deprived soil microbes by forcing air through unsaturated contaminated soil at low flow rates. This stimulates biodegradation and minimizes stripping volatiles into the atmosphere. Frequently used to remediate soil under structures since it is relatively non-invasive.
Biotrophic
Nutritional relationship between two organisms in which one or both must associate with the other to obtain nutrients and grow.
Blinding
(1) Clogging of the filter cloth of a vacuum filter, belt press, belt thickener, or pressure filter.
(2) Obstruction of the fine media of a sand filter.
Bloom
A proliferation of algae and/or higher aquatic plants in a body of water; often related to pollution, especially when pollutants accelerate growth.
Blower
A compressor designed to provide air to a biological reactor or aerobic digester to provide adequate dissolved oxygen in the fluid to support biological processes.
BNR
Biological Nutrient Removal
BOD
BOD is the biochemical oxygen demand of the wastewater (mg/l). The BOD is obtained from closed batch tests which operate for a number of days.
Bound water
(1) Water held strongly on the surface or in the interior of colloidal particles.
(2) Water associated with the hydration of crystalline compounds.
Breakpoint chlorination
Addition of chlorine to water or wastewater until the chlorine demand has been satisfied, with further additions resulting in a residual that is directly proportional to the amount added beyond the breakpoint.
Brush aerator
A surface aerator that rotates about a horizontal shaft with metal blades attached to it; commonly used in oxidation ditches.
Buffer
A solution which undergoes only a slight change in pH when H+ or OH- ions are added to it.
Buffer zone
A controlled clean area around a contaminated area for staging workers and preventing the spread of contamination during work.
Bulking sludges
Sludge with a sludge volume index (SVI) greater than 150 ml/mg.
Buoyancy
The upward force that acts on a body which is totally immersed in a fluid and is equal to the weight of the fluid displaced by the body.
Calcium hypochlorite [(Ca(OCl)2]
A solid that, when mixed with water, liberates the hypochlorite ion OCl- and can be used for disinfection. Commercial grades contain 70 percent available chlorine.
Calcium oxide (CaO)
A calcined chemical material known as lime. Used in lime and soda ash water treatment, but must first be slaked to calcium hydroxide [Ca(OH)2]. Also called burnt lime, quicklime, and unslaked lime.
Capsid
The protein coat of a virus.
Capsomere
An individual protein subunit of the virus capsid.
Capsule
Dense, well-defined polysaccharide or protein layer closely surrounding a cell. See glycocalx.
Carbohydrate
Any chemical compound which consists of only carbon (C), oxygen (O), and hydrogen (H) elements, for examples, sugars, starches, and cellulose are carbohydrates. Also the ratio of hydrogen to oxygen atoms in carbohydrates is usually 2:1.
Carbon
(1) A chemical element essential for growth.
(2) A solid material used for adsorption of pollutants.
Carbon dioxide
A nonflammable, colorless, odorless gas. Its molecules are composed of two oxygen atoms and one carbon atom.
Carbonaceous biochemical oxygen demand (CBOD)
A quantitative measure of the amount of dissolved oxygen required for the biological oxidation of carbon-containing compounds in a sample. See biochemical oxygen demand.
Carbon fixation
Conversion of carbon dioxide or other single-carbon compounds to organic forms such as carbohydrates
Carbonate hardness
Hardness caused by the presence of carbonates and bicarbonates of calcium and magnesium in water. Such hardness may be removed to the limit of solubility by boiling the water. When the hardness is numerically greater than the sum of the carbonate alkalinity and bicarbonate alkalinity, the amount of hardness is equivalent to the total alkalinity and is called carbonate hardness. It is expressed in milligrams of equivalent calcium carbonate per liter (mg/L CaCO3). See hardness.
Carbon-nitrogen (C/N) ratio
Ratio of the mass of organic carbon to the mass of nitrogen in soil or organic material
Catabolism
The biochemical processes involved in the breakdown of organic or inorganic compounds, usually leading to the production of energy.
Cation
A positively charged ion.
Cation exchange capacity
The ability to exchange negatively charged particles of two or more compounds, measured in milliequivalents per 100 grams.
Cationic flocculant
A polyelectrolyte with a net positive electrical charge.
Caustic alkalinity
The alkalinity caused by hydroxyl ions. See alkalinity.
Caustic soda
(sodium hydroxide) A white crystalline solids that, when dissolved in water, exhibits strong alkalinity and corrosiveness
Cell
The fundamental unit of life.
Celsius
The international name for the centigrade scale of temperature, on which the freezing point and boiling point of water are 0 degrees Celsius and 100 degrees Celsius, respectively, at 101 kPa (1 atm) of pressure. By international agreement, the term Celsius has replaced the term Centigrade.
Centigrade
By international agreement, the term Celsius has replaced the term Centigrade.
Cesspools
Underground tanks for raw sewage collection used where there is no sewage system.
Characterization.
The collection and analysis of information needed to define the hazardous material in an area or storage tank, such as planning, sample collection, laboratory analysis, collection of field data, statistical analyses, and reporting.
Chemical analysis
Analysis by chemical methods to show the composition and concentration of substances.
Chemical coagulation
The destabilization and initial aggregation of colloidal and finely divided suspended matter by the addition of an inorganic coagulant. See flocculation.
Chemical conditioning
Mixing chemicals with a sludge prior to dewatering to improve the solids separation characteristics. Typical conditioners include polyelectrolytes, iron salts, and lime.
Chemical dose
A specific quantity of chemical applied to a specific quantity of fluid for a specific purpose.
Chemical Dosing Facility
Equipment for administering measured dose of chemical to liquid. Used in phosphorus removal with the addition of metal salts and disinfection (i.e. chlorine).
Chemical equilibrium
The condition that exists when there is no net transfer of mass or energy between the components of a system. This is the condition in a reversible chemical reaction when the rate of the forward reaction equals the rate of the reverse reaction.
Chemical equivalent
The weight (in grams) of a substance that combines with or displaces 1 g of hydrogen. It is found by dividing the formula weight by its valence.
Chemical metering
The use of a variable-speed pump to control the dose of a chemical being used for a particular application.
Chemical Oxygen Demand (COD)
The quantity of O2 consumed in the oxidation of all the organic compounds, both biodegradable and recalcitrant, to CO2. Preferred to BOD, COD is a chemical property used to quantify the amount of organic matter in wastewater. The higher the chemical oxygen demand, the higher the amount of organic matter.
Chemical precipitation
(1) Formation of particulates by addition of chemicals.
(2) The process of softening water by the addition of lime or lime and soda to form insoluble compounds; typically followed by sedimentation or filtration to remove the newly created suspended solids.
Chemical reaction
A transformation of one or more chemical species into other species, resulting in the evolution of heat or gas, color formation, or precipitation. It may be initiated by a physical process such as heating, by the addition of a chemical reagent, or it may occur spontaneously.
Chemical Treatment
The process in which hazardous wastes are chemically changed to remove toxic contaminants from the environment. Type of treatment included in this account are oxidation, hydrolysis, photolysis, dechlorination, and electrolysis reactions. Includes process equipment and chemicals required for treatment.
Chemoautotroph
Organism that obtains energy from the oxidation of chemical, generally inorganic, compounds and carbon from carbon dioxide.
Chemoheterotroph
Organism that obtains energy and carbon from the oxidation of organic compounds
Chemolithotroph
An organism obtaining its energy from the oxidation of inorganic compoullds.
Chemoorganotroph
An organism obtaining its energy from the oxidation of organic compounds.
Chemostat
A conthluous culture device controlled by the concelltratiol1 of limiting nutrient and dilution rate
Chloramine
A compound composed of chlorine and ammonia.
Chlorinator
Any metering device used to add chlorine to water or wastewater.
Chlorine (Cl2)
An element ordinarily existing as a greenish-yellow gas approximately 2.5 times heavier than air. Because of its reactivity, chlorine does not exist in the free elemental state in nature. Chlorine is easily liquefied under pressure. Chlorine is a good bleaching agent because of its oxidizing properties
Chlorine Demand
The total amount of chlorine required to react with the organic and inorganic substances and to kill the bacteria in a water supply.
Chlorine dose
The amount of chlorine applied to a wastewater, typically expressed in milligrams per liter (mg/L) or pounds per million gallons (lb/mil. gal).
Chlorine Residual-Combined
Chlorine existing in the water as a chemical combination with ammonia or organic nitrogen compounds.
Chlorine Residual-Free Available
That residual chlorine existing in water as hypochlorous acid and hypochlorite ion.
Chlorination
A disinfection technique used in water treatment, involving the addition of Cl2 gas, chlorine dioxide, sodium hypochlorite or calcium hypochlorite. A highly effective disinfectant procedure for drinking water using chlorine gas or other chlorine-containing compounds as disinfectant (usually chloramines).
Chlorinator
A device that adds gaseous chlorine to water or sewage to kill infectious bacteria.
Chlorine-Contact Chamber
That part of a water treatment plant where effluent is disinfected by chlorine.
Chlorophyll and bacteriochlorophyl
Pigments of phototrophic organisms consisting of light sensitive magnesium tetrapyrroles.
Chloroplast
Organelle of photosynthetic eukaryotes containing chlorophyll and other pigments involved with photosynthesis for ATP synthesis. Was once a free-living cyanobacterium.
Ciliated protozoa
Microorganisms with cilia; common in trickling filters and healthy activated sludge. Free-swimming ciliates are present in the bulk liquid; stalked ciliates are commonly attached to solids matter in the liquid.
Cilium (plural, cilia)
Short, ( 520 µm) filamentous (hair-like) structure that beats with many others to make a cell move. (plural Cilia)
Citric acid cycle
A cyclical series of reactions resulting in the conversion of acetate to CO2 and NADH. Also called the Tricarboxylic ncid fJcle or the Kreb's cycle.
Clone
A population of cells all descended from a single cell; a number of copies of a DNA fragment obtained by allowing an inserted DNA fragment to be replicated by a phage or plasmid.
Clarification
Any process or combination of processes whose primary purpose is to reduce the concentration of suspended matter in a liquid; formerly used as a synonym for settling or sedimentation. In recent years, the latter terms are preferred to describe settling processes.
Clarifier
The clarifier, or secondary settler, is a large vessel or tank where the activated sludge solids are separated from the mixed liquor by gravity settling. Any large circular or rectangular sedimentation tank used to remove settleable solids in water or wastewater. A special type of clarifier, called an upflow clarifier, uses flotation rather than sedimentation to remove solids.
Coagulant
(1) A simple electrolyte, typically an inorganic salt containing a multivalent cation of iron, aluminum, or calcium [for example, FeCl3, FeCl2, Al2(SO4)3, and CaO].
(2) An inorganic acid or base that induces coagulation of suspended solids. See flocculant.
Coagulant or flocculant aid
An insoluble particulate used to enhance solid-liquid separation by providing nucleating sites or acting as a weighting agent or sorbent. Also used colloquially to describe the action of flocculants in wastewater treatment.
Coagulation
The conversion of colloidal (<0.001 mm) or dispersed (0.001 to 0.1 mm) particles into small visible coagulated particles (0.1 to 1 mm) by the addition of a coagulant, compressing the electrical double layer surrounding each suspended particle, decreasing the magnitude of repulsive electrostatic interactions between particles, and thereby destabilizing the particle. The water/wastewater treatment process of destabilizing colloidal particles to facilitate particle growth during flocculation by either double-layer compression, charge neturalization, interparticle bridging or precipitate enmeshment. See flocculation.
Coagulation basin
A basin used for the coagulation of suspended or colloidal matter, with or without the addition of a coagulant, in which the liquid is mixed gently to induce agglomeration with a consequent increase in the settling velocity of particulates.
Coccoid
Sphere shaped.
Coccus
A spherical bacterium.
COD
see Chemical oxygen demand - the amount of oxygen in mg/l required to oxidize both organic and oxidizable inorganic compounds
Coliforms
Gram negative, nonsporing, facultative rods that ferment lactose with gas formation within 48 hr at 35°C. Non-pathogenic bacteria present in the intestines of warm-blooded animals, water and wastewater, whose numbers indicate contamination. Escherichia coli and Enterobacter are important members.
Colony
A macroscopically visible population of cells growing on solid medium, arising from a single cell.
Colloidal Material/Colloids
The finely divided solids which will not settle but which may be removed by coagulation. Particulate matter of very fine size, usually in the range of 10-5 to 10-7 centimeters in diameter, and not prone to settling by subsidence. May be removed by coagulation, biochemical action, or membrane filtration; they are intermediate between true solutions and suspensions.
Combined sewer
A sewer intended to receive both wastewater and stormwater.
Combustion
A high temperature process involving the decomposition of organics in an excess of air.
Comminution
Shredding. A mechanical treatment process which cuts large pieces of waste into smaller pieces so that they won't plug pipes or damage equipment.
Complete mix
In a complete mix basin, the inflow is instantaneously mixed uniformly throughout the whole volume. Activated-sludge process whereby wastewater is rapidly and evenly distributed throughout the biological reactor.
Complex media
Culture media whose precise chemical composition is unknown. Also called undefined media.
Composite sample
A combination of individual samples of water or wastewater taken at pre-selected intervals to minimize the effect of the variability of the individual sample. Individual samples may be of equal volume or may be proportional to the flow at time of sampling.
Composting
The biological stabilization of wastes of biological origin under controlled conditions.
Concentration
(1) The amount of a given substance dissolved in a discrete unit volume of solution or applied to a unit weight of solid.
(2) The process of increasing the dissolved solids per unit volume of solution, typically by evaporation of the liquid.
(3) The process of increasing the suspended solids per unit volume of sludge as by sedimentation or dewatering
Conductivity
A measure of the ability of a solution to conduct an electrical current and is proportional to the concentration of ions in the solution. When measured with a standard apparatus, it is called specific conductance and expressed as micromhos. A function of the total dissolved solids.
Constructed wetland
A biological wastewater treatment system which utilizes plants for the degradation of organic waste.
Contact stabilization
A wastewater treatment plant in which there are two tanks, one for the adsorption of organic matter onto the suspended solids and another for oxidation of the adsorbed materials.
Contact tank
A tank used in water or wastewater treatment to promote contact among treatment chemicals or other materials and the liquid treated.
Contact time
The period of time that the material being processed is exposed to another substance, such as activated sludge or activated carbon, for completion of the desired reaction. See detention time.
Contamination
The introduction into water of microorganisms, chemicals, wastes, or wastewater in a concentration that makes the water unfit for its intended use.
Continuous-flow tank
A tank through which liquid flows continuously at its normal rate of flow, as distinguished from a fill-and-draw or batch system.
Conventional aeration
Process design configuration whereby the aeration tank organic loading is higher at the influent end than at the effluent end. Flow passes through a serpentine tank system, typically side-by-side, before passing on to the secondary clarifier. Also called plug flow.
Conventional treatment
Well-known or well-established water or wastewater treatment processes, excluding advanced or tertiary treatment. It typically consists of primary and secondary treatment.
Conversion factor
A numerical constant by which a quantity with its value expressed in units of one kind is multiplied to express the value in units of another kind.
Corrosion
The process of erosive deterioration in the physical form and engineered characteristics of a structure. These processes frequently involve electrolytic and/or corrosive chemical (eg, acids) effects which are sometimes mediated by microbial activities. It has been observed that corrosive pitting can form directly under biofilms
Cubic foot per second (cfs)
The rate of flow equal to one cubic foot of material per second; used for measurement of water, wastewater, or gas. Equals 2.832 x 10-2 m3/s.
Cubic meter per second (cms)
The rate of flow equal to one cubic meter of material per second; used for measurement of water, wastewater, or gas.
Culture
(verb) the act of successfully growing a unique strain or a consortium of microorganisms; (noun) a viable collection of a single strain of microorganisms which has been selectively grown. A particular strain or kind of organism growing in a laboratory medium.
Culture medium
An aqueous solution of various nutrients suitable for the growth of microorganisms.
Cyanobacteria
Prokaryotic oxygenic phototrophs containing chlorophyll a and phycobilins.
Cytochrome
Iron containing porphyrin complexed with proteins, which functions as an electron carrier in the electron transport system.
Cytoplasm
Cellular contents inside the cytoplasmic membrane, excluding the nucleus.
Cytoplasmic membrane
The permeability barrier of the cell, separating the cytoplasm from the environment.
DAF
Dissolved air flotation
Deactivation.
The process of placing a formerly active processing facility in a safe and stable condition until it can be decommissioned or dismantled. Facilities may not require full decontamination if surveillance and control of contamination is maintained.
Decant
to remove the liquid portion of a settled mixture without disturbing the sediment.
Dechlorination process
A process by which excess chlorine is removed from water to a desired level. Usually accomplished by chemical reduction, by passage through carbon beds or by aeration at a suitable pH.
Declining growth phase
Period of time between the log growth phase and the endogenous phase, where food is in short supply, leading to ever-slowing bacterial growth rates.
Decommissioning.
Activity that takes place after deactivation and includes surveillance and maintenance, decontamination, and/or dismantlement. These actions are taken to retire a facility from service while protecting workers, the public, and the environment.
Decomposer
Heterotrophic organism that breaks down organic compounds
Decomposition
The breakdown of complex material into simpler substances by chemical or biological processes.
Decomposition of wastewater
(1) The breakdown of organic matter in wastewater by bacterial action, either aerobic or anaerobic.
(2) Chemical or biological transformation of organic or inorganic materials contained in wastewater.
Defined media
Culture media whose exact chemical composition is known. Compare with Complex media
Degradable
That which can be reduced, broken down or chemically separated.
Degradation
The process by which a chemical is reduced to a less complex form.
Denitrification
Biological reduction of nitrite and nitrate to free nitrogen. Conversion of nitrate into nitrogen gases under anoxic conditions. The chemical reduction of nitrate and nitrite to gaseous
forms: nitric oxide, nitrous oxide and dinitrogen:
Deoxygenation
The depletion of dissolved oxygen in a liquid either under natural conditions associated with the biochemical oxidation of the organic matter present or by addition of chemical reducing agents.
Deoxygenation constant
A constant that expresses the rate of the biochemical oxidation of organic matter under aerobic conditions.
Deoxyribonucleic acid (DNA)
A polymer of nucleotides connected via a phosphate-deoxyribose sugar backbone; the genetic material of cells and some viruses.
Depth of blanket
Level of sludge in the bottom of a secondary clarifier.
Desiccation
Drying.
Design loadings
Flow rates and constituent concentrations that determine the design of a process unit or facility necessary for proper operation.
Detention time
The period of time that a water or wastewater flow is retained in a basin, tank, or reservoir for storage or completion of physical, chemical, or biological reaction. See contact time and retention time.
Detergent
(1) Any of a group of synthetic, organic, liquid, or water-soluble cleaning agents that are inactivated by hard water and have wetting and emulsifying properties but, unlike soap, are not prepared from fats and oils.
(2) A substance that reduces the surface tension of water.
Detoxification
Physical or chemical treatment to reduce or eliminate the toxicity of a material.
Dewater
(1) To extract a portion of the water present in a sludge or slurry.
(2) To drain or remove water from an enclosure. A structure may be dewatered so that it can be inspected or repaired.
Dideoxynucleotide
A nucleotide lacking the 3'-hydroxyl group on the deoxyribose sugar. Used in the Sanger method of DNA sequencing.
Differentiation
The modification of a cell in terms of structure and/or function occurring during the course of development.
Diffused aeration
Injection of air under pressure through submerged porous plates, perforated pipes, or other devices to form small air bubbles from which oxygen is transferred to the liquid as the bubbles rise to the water surface.
Diffusion aerator
An aerator that blows air under low pressure through submerged porous plates, perforated pipes, or other devices so that small air bubbles rise continuously through the water or wastewater.
Diffused air
Small air bubbles formed below the surface of a liquid to transfer oxygen to the liquid.
Diffuser
A porous plate, tube, or other device through which air is forced and divided into minute bubbles for diffusion in liquids. In the activated-sludge process, it is a device for dissolving air into mixed liquor. It is also used to mix chemicals such as chlorine to process streams.
Diffusion
The process by which gases and liquids spread themselves throughout any space into which they are put.
Digester
A tank or other vessel for the storage and anaerobic or aerobic decomposition of organic matter in sludge.
Digestion
(1) The biological decomposition of the organic matter in sludge, resulting in partial liquefaction, mineralization, and volume reduction.
(2) The process carried out in a digester.
Dikaryotic cell
Each fungal cell contains 2 genetically different haploid nuclei.
Demineralization
Removal from water of mineral contaminants. Methods include ion exchange, flash distillation, electrodialysis, or reverse osmosis.
Detention time
The time allowed for solids to collect in a settling tank. Theoretically detention time is equal to the volume of the tank divided by the flow rate.
Discrete settling
Particles settle as independent units, without interaction of flocs.
Disinfectant
An agent that kills microorganisms but may also be harmful to human tissue.
Disinfection
The process of eliminating nearly all pathogens, but not all microorganisms, from inanimate objects or surfaces.
Dissolved oxygen (DO)
A measure of the amount of oxygen dissolved in water,expressed as either:
(i) mg/L which is the absolute amount of oxygen dissolved in the water mass
(ii) as percentage saturation of the water with O2 (% sat)
Dissolved solids
The total colloidal and suspended solids in a liquid. Any particle passing a 1.2 µm filter is defined as dissolved.
Diurnal
(1) Recurring every day. (2) Occurring during the daytime, but not at night.
DNA fingerprinting
Molecular genetic techniques to assess possible differences among DNA in a samples.
DNA library
Collection of cloned DNA fragments which in total contain genes from the entire genome of an organism; also called a gene library.
Domain
The highest level of biological classification. The three domains of biological organisms are the Bacteria, the Archaea, and the Eukarya. Also used to describe a region of a protein having a distinct function.
Domestic wastewater
Wastewater derived principally from nonindustrial sources (e.g., dwellings, business buildings, institutions, etc.).
Doubling time
The time needed for a population to double. See also Generation time.
Dry weather flow
The combination of wastewater and dry weather infiltration flowing in a sanitary sewer during times of low precipitation.
E. coli
See Escherichia coli.
Ecology
Study of the interrelationships between organisms and their environments.
Ecosystem
A community of organisms and their natural environment.
Effervescence
The vigorous escape of small gas bubbles from a liquid, especially as a result of chemical action.
Effluent
Wastewater or other liquid, partially or completely treated or in its natural state, flowing out of a reservoir, basin, treatment plant, or industrial treatment plant, or part thereof.
Effluent quality
The physical, biological, and chemical characteristics of a wastewater or other liquid flowing out of a basin, reservoir, pipe, or treatment plant.
Effluent Polishing or Tertiary Treatment
A further stage of treating sewage or effluents, by removing suspended solids and or pollutants. Consequential removal of suspended solids may also remove residual BOD or other pollutants.
Electrical double layer
A name given to the combination of the Stern layer and the diffused layer of both negatively and positively charged ions which surround it.
Electron acceptor
A substance that accepts electrons during an oxidation-reduction reaction. An electron acceptor is an oxidant.
Electron donor
A compound that donates electrons in an oxidation-reduction reaction. An electron donor is a reductant.
Electrophilic compounds
Chemicals that attack or are drawn to regions in other chemicals in which electrons are readily available; oxidizing agents act as electrophilic compounds.
Electron transport phosphorylation
Synthesis of ATP involving a membrane-associated electron transport chain and the creation of a proton motive force. Also called Oxidative phosphorylation.
Endocytosis
A process in which a particle such as a virus is taken intact into an animal cell. Phagocytosis and pinocytosis are two kinds of endocytosis.
Endogenous respiration
Autooxidation by organisms in biological processes. A reduced level of respiration (breathing) in which organisms break down compounds within their own cells to produce the oxygen they need.
Endoplasmic reticulum
An extensive array of internal membranes in eukaryotes.
Enrichment culture
Use of selective culture media and incubation conditions to isolate microorganisms from natural samples.
Enteric bacteria
General term for a group of bacteria that inhabit the intestinal tract of humans and other animals. Among this group are pathogenic bacteria such as Salmonella and Shigella.
Enterococci
A group of cocci that normally inhabit the intestines of man and animals. No to be confused with fecal Streptococci.
Entrainment
The trapping of bubbles in a liquid produced either mechanically through turbulence or chemically through a reaction
Entropy
A measure of the degree of disorder in a system; entropy always increases in a closed system.
Environmental Impact Statement.
A report that documents the information required to evaluate the environmental impact of a project. It informs decision makers and the public of the reasonable alternatives that would avoid or minimize adverse impacts or enhance the quality of the environment.
Environmental indicator
A measure to identify the presence or condition of a phenomenon that is affecting the environment. A combination of indicators and trend analysis provides a general picture of the overall quality of the environment.
Enzyme A
catalyst, usually composed of protein, that promotes specific reactions or groups of reactions.
Environmental impact assessment (EIA)
A review to which all commencing
projects must be subjected with regard to their impact on the environment.
Epilimnion
The zone in a stratified lake just below the near-surface water in which temperature.
EPS
Extracellular polymeric substances (extracellular polsaccharide, exocellular polysaccharide), many microorganisms do produce an "overcoat" of polymers outside of the cell. These polymers bind water and various chemicals to form protective and storage functions.
Equilibrium
A condition of balance in which the rate of formation and the rate of consumption or degradation of various constituents are equal. See chemical equilibrium.
Equilibrium concentration
The concentration of the dissociated ions when the rates of both backward and forward reactions are equal.
Equilibrium constant
A value that describes the quantitative relationship between chemical species in a system at equilibrium.
Equilization basin
A holding tank within which variations in sewage inflow rate and liquid nutrient concentrations are averaged.
Equivalence
The number of protons donated in an acid-base reaction or the total change in valence in an oxidation-reduction reaction.
Equivalent calcium carbonate
A common form of expressing the hardness, acidity, total alkalinity, carbon dioxide, carbonate, bicarbonate, noncarbonate, or hydroxide content of water expressed in milligrams per liter (mg/L). It is calculated by multiplying the number of chemical equivalents of any of these constituents present in 1 L by 50, the equivalent weight of calcium carbonate. See chemical equivalent.
Equivalent Population
A flow-based unit of measurement used to indicate sewage load and a flow of 240 litres per day is usually defined as one EP.
Escherichia coli
- A species of bacteria found in large numbers in the intestinal tract of warm blooded animals.
Essential nutrients
Inorganic substances such as nitrogen, phosphorus, and iron that are required in small quantities for biological processes to occur.
Euglena
A motile unicelluler freshwater autotrophic organism traditionally classified as a plantlike member of the kingdom Protista (algae).
Eukarya
The phylogenetic domain containing all eukaryotic organisms.
Eukaryote
A cell or organism having a unit membrane-enclosed (true) nucleus and usually other organelles.
Eutrophic
Having high concentrations of nutrients optimal, or nearly so, for plant or animal growth. Can be applied to nutrient or soil solutions and bodies of water. Describes a water body that has built up excess nutrients, so that excess plant growth can occur.
Eutrophication
The enrichment of water in watercourses and lakes by chemical substances, especially compounds of nitrogen and phosphorous. An increase in the concentration of nutrients in an aquatic ecosystem, causing:
(i) the increased productivity of autotrophic green plants,
leading to the blocking out of sunlight
(ii) elevated temperatures within the water body
(iii) depletion of the world's oxygen resources
(iv) increased agal growth
(v) reduction in the level of and variety of fish and animal
Evaporation
The changing of liquid water from rivers, lakes, bare soil and vegetative surfaces into water vapor.
Exothermic reaction
A chemical reaction during which heat is liberated.
Exponential growth
Growth of a microorganism where the cell number doubles within a fixed time period.
Exponential growth phase
A phase of microbial population growth rate where the number of cells doubles during a certain period of time. Environmental conditions are ideal (ample food, suitable temperature, etc) for exponential growth to occur.
Exponential phase
A period during the growth cycle of a population in which growth increases at an exponential rate.
Extended aeration
The extended aeration process is a type of secondary (biological) treatment.
It is a modification of the conventional activated sludge process and
operates in the endogenous phase of growth, in which there is not enough
food remaining in the system to support all of the microorganisms present.
The microorganisms are aerated and suspended within the sewage, where
aerobic degradation of the pollutants takes place. Residence time is of the
order of 24 hours compared to around 6 hours in conventional activated
sludge tanks.
ex situ
A Latin term meaning off-location.
Extended aeration
Involves an aeration period of more than 24 hours and a high rate of return sludge to allow cell decay during the endogenous respiration phase of the growth curve.
Extracellular
Outside the cell.
Extreme halophile
An organism whose growth is dependent on large amounts (generally >10%) of NaCl.
Extremophile
An organism that grows optimally under one or more chemical or physical extremes, such as high or low temperature or pH.
F/M Ratio
The food to microorganism ratio uaed to provide a broad indication of the amount of biodegradable material (or load) entering the treatment plant, as a function of time. Since BOD is used as one of the parameters and the term M is based upon the MLVSS or mixed liquor volatile suspended solids, F/M is usually an historical measure rather than a control parameter. Similarly F/M determination would usually be subject to significant error and variability particularly over changes of sludge age.
Facultative
A qualifying adjective indicating that an organism is able to grow in either the presence or absence of an environmental factor (for example, "facultative aerobe"). Facultative aerobes/anaerobes Having the ability to live either with or without oxygen
Facultative bacteria
Bacteria that can grow and metabolize in the presence and absence of dissolved oxygen.
Fahrenheit
A temperature scale in which water freezes at 0 degrees Celsius (32 degrees Fahrenheit (°F)) and boils at 100° Celsius (212° Fahrenheit (°F)) at atmospheric pressure.
Faecal coliforms
Thermotolerant coliform organisms mainly indicating faecal pollution. Escherihia coli is generally the dominant species.
Fecal coliform bacteria
Aerobic and facultative, Gram-negative, non-spore-forming, rod-shaped bacteria capable of growth at 44.5 degrees Celsius (112 degrees Fahrenheit (°F)) and associated with fecal matter of warm-blooded animals. Their presence in water or sludge is an indicator of pollution and possible contamination by pathogens.
Fecal indicators
Fecal coliform, fecal streptococci, and other bacterial groups originating in human or other warm-blooded animals, indicating contamination by fecal matter.
Fecal streptococci
The subgroup of enterococci that is of particular concern in water and wastewater
Fermentation
Catabolic reactions producing ATP in which organic compounds serve as both primary electron donor and ultimate electron acceptor and ATP is produced by substrate-level phosphorylation.
Ferric chloride (FeCl3)
A soluble iron salt often used as a sludge conditioner to enhance precipitation or bind up sulfur compounds in wastewater treatment. See coagulant.
Ferric sulfate (Fe2(SO4)3)
A water-soluble iron salt formed by reaction of ferric hydroxide and sulfuric acid or by reaction of iron and hot concentrated sulfuric acid. Also obtainable in solution by reaction of chlorine and ferrous sulfate. Used in conjunction with lime as a sludge conditioner to enhance precipitation.
Ferrous chloride (FeCl2)
A soluble iron salt used as a sludge conditioner to enhance precipitation or bind up sulfur. See coagulant.
Ferrous sulfate (FeSO4.7H2O)
A water-soluble iron salt, sometimes called copperas; used in conjunction with lime as a sludge conditioner to enhance precipitation.
Filamentous
In the form of very long rods, many times longer than wide.
Filamentous bactera
a Filamentous bacteria are long and narrow in appearance. In high concentrations, they produce strong, but poorly compacting flocs which have a high SVI. They are the cause of bulking.
Filter
A device or structure for removing solid or colloidal material, typically of a type that cannot be removed by sedimentation, from water, wastewater, or other liquid. The liquid is passed through a filtering medium, typically a granular material but sometimes finely woven cloth, unglazed porcelain, or specially prepared paper.
Filter cloth
A fabric stretched around the drum of a vacuum filter.
Filtered wastewater
Wastewater that has passed through a mechanical filtering process.
Filtrate
The liquid that has passed through a filter.
Filtration
A process whereby suspended and (some) colloidal matter is removed from water and wastewater by passage through a granular medium. A treatment process for removing solid (particulate) matter from water by passing the water through porous media such as sand or a man-made filter.
Fimbria (plural fimbriae)
Short, filamentous structure on a bacterial cell; although flagella-like in structure, generally present in many copies and not involved in motility. Plays a role in adherence to surfaces and in the formation of pellicles. See also Pilus.
Final effluent
The effluent from the final treatment unit of a wastewater treatment plant.
Final sedimentation
The separation of solids from wastewater in the last settling tank of a treatment plant.
FISH
Fluorescent in-situ hybridization; a process in which a cell is made fluorescent by labeling it with a specific nucleic acid probe that contains an attached fluorescent dye.
Five-day biochemical oxygen demand (BOD5)
A measure of the amount of oxygen used by bacteria to degrade organic matter in a sample of wastewater over a 5 day period at 20 ÷C, expressed in mgL-1.
Fixed solids
The residue of total suspended or dissolved solids after ignition or heating for a specified time at a specified temperature.
Flagellates
A varied group of one-celled organisms in the kingdom Protista that possess flagella, which are used for locomotion.
Flagellum (plural flagella)
A thin, filamentous organ of motility in prokaryotes that functions by rotating. Long whip-like or feathery structure borne singly or in small numbers by motile cells of many bacterial and unicellular eukaryotes like the protozoa. Structures of prokaryotic and eukaryotic flagella and their modes of action differ.
Flexibacter
Seldom or incidentally observed filament (reported in approx 1% of plants surveyed). Organism is motile by a flexing or twitching action.
Flight
A scraper in a rectangular sedimentation tank with blades that move sludge along the bottom of the tank to a collection point. As the flights return, scum is collected on the surface of the tank and pushed to an outlet point.
Flocs
Bacteria exist in the system as aggregates called flocs. These flocs are a flocculated mass of bacteria, organic and inorganic material collectively called activated sludge. Flocs typically vary in size from 10 to 300 microns or larger.
Flocculant
Water-soluble organic polyelectrolytes that are used alone or in conjunction with inorganic coagulants to agglomerate the solids present in water. This process forms large, dense floc particles that settle rapidly.
Flocculating tank
A tank used for the formation of floc by the gentle agitation of liquid suspensions, with or without the aid of chemicals.
Flocculation.
Aggregation of small particles into larger particles. Flocculation The water treatment process in which particle collisions are
induced in order to encourage the growth of larger particles.
Flocculation agent
A coagulating substance that, when added to water, forms a flocculent precipitate that will entrain suspended matter and expedite sedimentation. Examples are alum, ferrous sulfate, and lime.
Flocculator
A mechanical device to enhance the formation of floc in a liquid.
Flotation
A process by which suspended matter is lifted to the surface of a liquid to facilitate its removal. Frequently done by the bubbling of air through the liquid.
Flow
(1) The movement of a stream of water or other fluid from place to place. The movement of silt, water, sand, or other material.
(2) The fluid that is in motion.
(3) The quantity or rate of movement of a fluid discharge; the total quantity carried by a stream.
(4) To issue forth or discharge.
(5) The liquid or amount of liquid per unit time passing a given point.
Flow equalization
Transient storage of wastewater for release to a sewer system or wastewater treatment plant at a controlled rate to provide a reasonably uniform flow for treatment.
Fluorescent
Having the ability to emit light of a certain wavelength when activated by light of another wave-length.
Foam
(1) A collection of minute bubbles formed on the surface of a liquid by agitation, fermentation, and so on.
(2) The frothy substance composed of an aggregation of bubbles on the surface of liquids and created by violent agitation or by the admission of air bubbles to liquid containing surface-active materials, solid particles, or both.
Food/micro-organism ratio (F/M)
A measure of the organic loading rate of a wastewater treatment system, i.e. the ratio between the daily BOD load and the quantity of activated sludge in the system (microbes). In the activated-sludge process, the loading rate expressed as pounds of BOD per kilograms of mixed liquor or mixed liquor volatile suspended solids per second (mg/kg·s) or pounds of BOD per pound of mixed liquor or mixed liquor volatile suspended solids per day [lb BOD/d/lb MLSS or MLVSS].
Forced aeration
The bringing about of intimate contact between air and liquid where the air, under pressure, is applied below the surface of the liquid through diffusers or other devices that promote the formation of small bubbles.
Formazine turbidity unit (FTU)
A standard unit of turbidity based on a known chemical reaction that produces insoluble particulates of uniform size. The FTU has largely replaced the JTU. Also known as nephelometric turbidity unit.
Fouling
A gelatinous, slimy accumulation resulting from the activity of organisms in the water. Fouling may be found on concrete, masonry, or metal surfaces.
Free oxygen
Elemental oxygen (O2).
Free-swimming ciliate
Mobile, one-celled organisms using cilia (hairlike projections) for movement.
Free wate
r Suspended water constituting films covering the surface of solid particles or the walls of fractures, but in excess of pellicular water; mobile water is free to move in any direction under the pull of the force of gravity and unbalanced film pressure.
Freeboard
The vertical distance between the normal maximum level of the surface of the liquid in a conduit, reservoir, tank, or canal and the top of the sides of an open conduit or the top of a dam or levee that is provided so that waves and other movements of the liquid will not overflow the confining structure.
Frequency
(1) The time rate of vibration or the number of complex cycles per unit time.
(2) The number of occurrences of a certain phenomenon in a given time.
Fresh sludge
Sludge in which decomposition is little advanced.
Fresh wastewater
Wastewater of recent origin containing dissolved oxygen.
Fruiting body
A macroscopic reproductive structure produced by some fungi (for example, mushrooms) and some Bacteria (for example, myxobacteria), each distinct in size, shape, and coloration.
Fungi
Nonphototrophic eukaryotic microorganisms that contain rigid cell walls. Small non-chlorophyll-bearing plants that lack roots, stems, or leaves, occur (among other places) in water, wastewater, or wastewater effluents, and grow best in the absence of light. Their decomposition may cause disagreeable tastes and odors in water. In some wastewater treatment processes they are desirable and in others they are detrimental.
G + C base ratio
In DNA (or RNA) from any organism, the percentage of the total nucleic acid that consists of guanine plus cytosine bases (expressed as mol % GC).
Gallons per day (gpd)
A unit of measurement for the flow rate of water, wastewater, or other liquid.
Gallons per minute (gpm)
A unit of measurement for the flow rate of water, wastewater, or other liquid.
Gas production
The creation of a gas by chemical or biological means.
G-bacteria
Bacteria with a tetrad arrangment seen in activated sludges.
Gene
A unit of heredity; a segment of DNA specifying a particular protein or polypeptide chain, a tRNA or an rRNA.
Gene probe
A strand of nucleic acid which can be labeled and hybridized to a complementary molecule from a mixture of other nucleic acids.
Generation time
Time needed for a population to double. See also Doubling time.
Genome
The complete set of genes present in an organism,
Genotype
The precise genetic constitution of an organism.
Genus (plural, genera)
A taxonomic group of related species.
Germicide
A substance that inhibits or kills microorganisms.
Glycocalyx
A term that describes polysaccharide components outside of the bacterial cell wall; usually a loose network of polymer fibers extending outward from the cell. See capsule.
Glycolysis
Reactions of the Embden-Meyerhof pathway in which glucose is oxidized to pyruvate.
Grab sample
A sample taken at a given place and time. It may not be representative of the entire volume of material. See composite sample.
Gradient
The rate of change of any characteristic per unit of length or slope. The term is typically applied to such things as elevation, concentration or pressure.
Gram negative cell
A prokaryotic cell whose cell wall contains relatively little peptidoglycan but has an outer membrane composed of lipopolysaccharide, lipoprotein, and otller complex macromolecules. Bacteria stain red (negative) with Gram stain.
Gram positive cell
A prokaryotic cell whose cell wall consists chiefly of peptidoglycan and lacks the outer membrane of gram negative cells. Bacteria stain blue-black to purple (positive) with Gram stain.
Gram stain
A commonly used bacterial stain using Crystal violet and iodine with a Safranin counter stain to differentiate bacteria on the basis of cell wall structure. See Gram positive cell and Gram negative cell.
Grazing
See Predation.
Growth
In microbiology, an increase in cell number.
Growth factor analog
A chemical agent that is related to and blocks the uptake or utilization of a growth factor.
Growth rate
The rate at which growth occurs, usually expressed as the generation time.
Growth rate constant
Slope of log 10 of the number of cells per unit volume plotted against time.
Growth yield coefficient
Quantity of biomass carbon formed per unit of substrate carbon consumed.
Habitat
The location in nature where an organism resides.
Haliscomenobacter hydrossis
Found reasonably often in incidental/low quantities, this organism is reported to be associated with low F/M and low DO.
Halogen
The reactive members of Group 7 of the Periodic Table, including chlorine, bromine, fluorine and iodine.
Halophile
An organism requiring salt (NaCl) for growth.
Halotolerant
Capable of growing in the presence of NaCl, but not requiring it.
Halotrophs
Microorganisms able to survive and grow in brine solutions. Some of these organisms cannot even survive when the salt concentration is less than 12%.
Hardness in water
The sum of the calcium and magnesium ion concentrations. A hard water will leave a scale on the inside of kettles and will form a scum rather than a lather with soap.
Head
(1) The height of the free surface of fluid above any point in a hydraulic system; a measure of the pressure or force exerted by the fluid.
(2) The energy, either kinetic or potential, possessed by each unit weight of a liquid, expressed as the vertical height through which a unit weight would have to fall to release the average energy possessed. It is used in various compound terms such as pressure head, velocity head, and loss of head.
(3) The upper end of anything, such as a headworks.
(4) The source of anything, such as a headwater.
Head loss
Energy losses resulting from the resistance of flow of fluids. May be classified into conduit surface and conduit form losses.
Header
(1) A large pipe installed to intercept the ends of a series of pipes; a manifold. (2) The closing plate on the end of a sewer lateral that will not be used immediately.
Headworks
The initial structures and devices of a water or wastewater treatment plant.
Heterocyst
A differentiated cyanobactenal cell that carries out nitrogen fixation.
Heterotroph
Chemoorganotroph. A microorganism which requires organic compounds for its source of carbon. Organism capable of deriving carbon and energy for growth and cell synthesis from organic compounds; generally also obtain energy and reducing power equivalents from organic compounds.
Heterotrophic
A term applied to organisms which need ready-made food materials from which to produce their own constituents and to obtain all their energy.
Heterotrophic bacteria
Microorganisms that cannot synthesize their own food and, therefore, depend on other organisms for it. The majority of heterotrophic bacteria are saprotrophs (also called decomposers), organisms that obtain their food from dead organic matter. Other heterotrophic bacteria are parasites, organisms that depend on other living organisms for food.
Heterotrophic nitrification
Biochemical oxidation of ammonium to nitrite and nitrate by heterotrophic microorganisms.
High-purity oxygen
A modification of the activated-sludge process using relatively pure oxygen and covered biological reactors in a conventional flow arrangement.
High-purity oxygen activated-sludge process
A modification of the activated-sludge process where high-purity oxygen is used instead of air to provide dissolved oxygen in the mixed liquor.
High-rate activated-sludge process
A modification of the activated-sludge process whereby the mixed liquor suspended solids loadings are kept high, allowing high food-to-microorganisms ratios and shorter detention times.
Homogenous
Consisting of only one phase.
Hydrated lime
Limestone that has been "burned" and treated with water under controlled conditions until the calcium oxide portion has been converted to calcium hydroxide.
Hydraulic loading
The amount of water applied to a given treatment process, typically expressed as volume per unit time, or volume per unit time per unit surface area.
Hydraulic residence time (HRT)
Used as an expression of the average time the influent spends in the aerobic reactor in the activated sludge system. It has units of days.
Hydraulic surge
A sudden increase in the flow rate through a component or an entire process.
Hydrocarbon
Any chemical compound containing only carbon and hydrogen elements. Some simple examples of hydrobarbons are: methane (CH4), ethylene (C2H4), ethane (C2H6), etc
Hydrogen bond
Chemical bond between a hydrogen atom of one molecule and two unshared electrons of another molecule.
Hydrogen Sulfide (H2S)
A toxic and malodorous gas emitted during organic decomposition in the absence of air.
Hydrogen-ion concentration
The concentration of hydrogen ions in moles per liter of solution (moles/L). Commonly expressed as the pH value, which is the logarithm of the reciprocal of the hydrogen-ion concentration.
Hydrolysis
A process whereby particulate or high molecular weight soluble substrates are broken down to smaller molecules by the incorporation of water molecules. In anaerobic conditions hydrolysis is catalysed by hydrolytic enzymes excreted by bacteria. Breakdown of a polymer into smaller units, usually monomers, by addition of water; digestion.
Hydrophilic
Water attracting or attracted to water, as polar groups on compounds such as proteins. Displaying an affinity for water.
Hydrophobic
Water repelling or repelled by water, as non-polar groups on lipids or proteins which tend to aggregate, excluding water. Displaying an aversion for water.
Hydrophobic interactions
Attractive forces between mol ecules due to the close positioning of nonhydropllilic portions of the two molecules.
Hyperthermophile
A prokaryote having a growth temperature optimum of 80°C or higher.
Hypochlorite
Calcium, sodium, or lithium hypochlorite
Imhoff cone
A cone-shaped graduated vessel used to measure the volume of settleable solids in various liquids of wastewater origin during various settling times.
Impeller
A rotating set of vanes designed to impel rotation of a mass of fluid.
Incubation
The act of growing an organism under conditions that will encourage rapid growth (compared to natural conditions).
Indicator/Indicator Organism
In biology, an organism, species, or community whose characteristics show the presence of specific environmental conditions.
Induction period
The period of adaptation that an organism has to pass through before it is able to flourish in a favorable habitat.
Industrial wastewater
Wastewater derived from industrial sources or processes.
Infiltration/Inflow
Stormwater or groundwater which enters the sewerage system through cracked pipes or defective joints.
Inorganic
Material or molecules not containing carbon.
In situ
At site.
Intermittently Decanted Extended Aerated (IDEA)
An activated sludge, sewage treatment process in which biological treatment and settlement of solids (clarification) are combined in the one reactor. Sewage inflow occurs continuously but effluent outflow occurs intermittently (at a higher flow rate) after a period of quiescent conditions.
Intracellular
Inside the cell.
In vitro
In glass, away from the living organism.
In vivo
In the body, in a living organism.
Inhibition
Prevention of growth or function.
Inoculum
Material used to initiate a microbial culture.
Ion
A charged atom, molecule, or radical that affects the transport of electricity through an electrolyte or, to a certain extent, through a gas. An atom or molecule that has lost or gained one or more electrons.
Ion exchange
(1) A chemical process involving reversible interchange of ions between a liquid and a solid, but no radical change in structure of the solid.
(2) A chemical process in which ions from two different molecules are exchanged.
(3) The reversible transfer or sorption of ions from a liquid to a solid phase by replacement with other ions from the solid to the liquid.
Iron oxidising bacteria
Those bacteria able to oxidise iron by any means from a reduced form of iron (ferrous form) to an oxidised (ferris) state.
Iron reducing bacteria
Those bacteria which are able to reduce iron by any means from an oxidised form (ferric) to a reduced (ferrous) state.
Iron related bacteria (IRB)
Those bacteria which are able to accumulate iron in another form beyond that for basic metabolic functioning. These accumulated iron compounds generally collect within the slime (EPS) around the cells and gradually harden (crystallise) over time.
Jackson turbidity unit (JTU)
A standard unit of turbidity based on the visual extinction of a candle flame when viewed through a column of turbid water containing suspended solids. It varies with the solids composition (barium sulfate, diatomaceous earth, and so on). The JTU has largely been replaced by the more reproducible nephelometric turbidity unit (NTU).
Jar test
A laboratory procedure for evaluating coagulation, flocculation, and sedimentation processes in a series of parallel comparisons.
Jet
The stream of water under pressure issuing from an orifice, nozzle, or tube.
Jet aeration
A method of adding dissolved oxygen to mixed liquor by injecting an air-water mixture through nozzles into the reactor.
Johannesburg Process
Based on the 3 stage Phoredox Process with the addition of a reactor in the sludge recycle line. This reactor served the purpose to extend retention time of the return sludge prior to the anaerobic zone to allow endogenous denitrification to occur. The rate of endogenous denitrification (mg nitrate-N/d) is higher in this reactor due to the higher solids concentration and can result in a reduced sludge nitrate concentration to acceptable levels prior to entry to the anaerobic zone which protects the P removal capacity of the plant. This reactor often takes the form of an anoxic zone at the head of the plant giving a process train which is anoxic, anaerobic, anoxic, aerobic. The sludge denitrification zone is usually quite small to maintain the anaerobic:anoxic:aerobic mass fraction ratios within acceptable limits.
Joule (J)
A unit of energy equal to 107 ergs; 1000 Joules equal 1 kilojoule (kJ).
Kinetics
The study of the rates at which changes occur in chemical, physical, and biological treatment processes.
Kjeldahl nitrogen
The combined amount of organic and ammonia nitrogen. Also called total Kjeldahl nitrogen (TKN).
Kraus process
A modification of the activated-sludge process in which aerobically conditioned supernatant liquor from anaerobic digesters is added to activated sludge biological reactors to improve the settling characteristics of the sludge and to add an oxygen resource in the form of nitrates.
Lagoon
In wastewater treatment, a large earthen basin used for extended aeration processes or to hold excess influent during high-flow episodes.
Lag phase
The period after inoculation of a population before growth begins.
Lateral gene transfer
The exchange of genes between and among cells in a microbial community not involving vertical transfer from one cell to its offspring. Also called horizonta1 gene transfer.
Lethal concentration
The concentration of a test material that causes death of a specified percentage of a population, typically expressed as the median or 50 percent level (LD50).
Lime
Any of a family of chemicals consisting essentially of calcium hydroxide made from limestone (calcite) composed almost wholly of calcium carbonate or a mixture of calcium and magnesium carbonate; used to increase pH to promote precipitation reactions or for lime stabilization to kill pathogenic organisms.
Limiting nutrient
A major nutrient which is in short supply and restricts the growth of a biomass. Limitations could also be created by the limiting nutrient distorting the ratios of nutritional elements outside of range that would support growth.
Lipid
Water insoluble organic molecules important in structure of the cytoplasmic membrane and (in some organisms) the cell wall. See also Phospholipid.
Lithotrophic
A term describing organisms which use inorganic compounds as
electron donors in their energetic processes.
Lysis
Rupture of a cell, resulting in a loss of cell contents.
Macromolecule
A large molecule (polymer) formed by the connection of a number of small molecules (monomers).
Macronutrient
A nutrient like potassium or magnesium which is required by cells in high amounts compared to trace elements.
Mass balance
Based on the premise that mass can be neither created nor destroyed, this procedure helps to map out the location of mass within a system.
Mean cell residence time (MCRT)
The average time a single microbe willremain in an activated sludge system and is calculated by: Total mass ofcells/Rate of cell wastage.
Mechanical Aeration
(1) Mixing, by mechanical means, of wastewater and activated sludge in the biological reactor of the activated-sludge process to bring fresh surfaces of liquid into contact with the atmosphere.
(2) The introduction of atmospheric oxygen into a liquid by the mechanical action of paddle, paddle wheel, spray, or turbine mechanisms.
Mechanical disruption
The use of physical methods (such as freezing, ultrasonics, pressure pulses, radical thermal gradients) to disrupt a biofouling event.
Membrane
Any thin sheet or layer. See especially Cytoplasmiic membrane.
Membrane filtration (MF)1
Techniques such as microfiltration, nanofiltration and reverse osmosis used in tertiary treatment processes to produce high-grade effluents for specific purposes.
Membrane filtration (MF)2
The use of a non-absorbent porous membrane to trap particles (including bacteria) which allow the water to filter through. It is a technique used to enumerate low numbers of bacteria in water by concentration the cells on the filters surface where they may be grown to form visible countable colonies. Pore sizes commonly employed are of 0.22 and 0.45 microns diameter
Mesophilic temperatures
Those temperatures in the range 10 45 °C.
Metabolism
All biochemical reactions in a cell, both anabolic and catabolic (both synthesis and breakdown of organic materials).
Metazoa
A group of animals having bodies composed of cells differentiated into tissues and organs and typically have a digestive cavity lined with specialized cells.
Methane (CH4)
A colorless, odorless, flammable, gaseous hydrocarbon present in natural gas and formed by the anaerobic decomposition of organic matter, or produced artificially by heating carbon monoxide and hydrogen over a nickel catalyst.
Methane bacteria
A specialized group of obligate anaerobic bacteria that decompose organic matter to form methane.
Methanogen
A methane producing prokaryote; member of the Archaea.
Methanogenesis
In this terminal step of anaerobic digestion, methane is produced from the decarboxylation of acetate (acetoclastic methanogens) and from the reduction of carbon dioxide and hydrogen (hydrogen utilising methanogens).
Methanotroph
An organism capable of oxidizing methane.
Methylotroph
An organism capable of oxidizing organic compounds that do not contain carbon-carbon bonds; if able to oxidize CH4, also a methanotroph.
Microaerophilic
Requiring O2 but at a level lower than atmospheric.
Microbial activity
Activities of microorganisms resulting in chemical or physical changes.
Microbial film
A gelatinous film of microbial growth attached to or spanning the interstices of a support medium. Also called biological slime.
Microbiology
The study of bacteria, including their classification and the prevention of disease caused by bacterial infection.
Microenvironment
The immediate physical and chemical surroundings of a microorganism.
Microfauna
Protozoa, nematodes and arthropods generally <200 micrometers long
Microfiltration
The process of passing wastewater through porous membranes in the form of sheets or tubes to remove suspended and particulate material. Pore sizes can be very small and particles down to 0.2 microns can be filtered.
Microflora
Bacteria (including actinomycetes), fungi, algae, and viruses
Micrometer
One millionth of a meter, or 10-6 m (abbreviated µm), the unit used for measuring wavelengths of light and microscopically small objects including microorganisms.
Micronutrient
Chemical element necessary for growth found in small amounts, usually < 100 mg kg -1 in a plant. These elements consist of B, Cl, Cu, Fe, Mn, Mo, and Zn
Microorganism (microbe)
A microscopic organism consisting of a single cell or cell cluster, also including the viruses. Living organism too small to be seen with the naked eye (< 0.1 mm).
Microthrix parvicella
Most commonfilament seen in most bulking and foaming plants and almost always recorded in plants surveyed. Occurs in plants with a wide range of operating conditions and configurations. Characterized by its Gram positive response and its usual tangled mass of twisted and unbranched filaments.
Milligrams Per Liter (mg/l)
Numerically the same as parts per million when applied to water.
Million gallons per day (mgd)
A measure of flow equal to 1.547 ft3/sec, 681 gallons per minute, or 3.785 m3/d.
Mineralization
The process by which organic N is reconverted to mineral form by a wide variety of heterotrophic organisms bacteria, fungi and actinomycetes.
Mixed liquor
A mixture of raw or settled wastewater and activated sludge contained in an aeration tank in the activated-sludge process. See mixed liquor suspended solids.
Mixed Liquor Suspended Solids (MLSS)
The total amount (comcentration) of inorganic and organic material in suspension in the mixed liquor in the aerobic reactor. It is quantified in the same way as SS and has the same units (mg/l).
Mixed liquor volatile suspended solids (MLVSS)
That fraction of the suspended solids in activated sludge mixed liquor that can be driven off by combustion at 550 degrees Celsius. It indicates the concentration of microorganisms available for biological oxidation
Mixing basin
A basin or tank in which agitation is applied to water, wastewater, or sludge to increase the dispersion rate of applied chemicals; also, tanks used for general mixing purposes.
Mixing chamber
A chamber used to facilitate the mixing of chemicals with liquid or the mixing of two or more liquids of different characteristics. It may be equipped with a mechanical device that accomplishes the mixing.
Mixing channel
A channel provided in a water or wastewater treatment plant; the hydraulic characteristics of the waterway or its construction features are such that chemicals or liquids are thoroughly mixed.
Mixotroph
An organism able to assimilate organic compounds as carbon sources while using inorganic compounds as electron donors for energy metabolism. Compare with autotroph and heterotroph.
MLSS
See Mixed Liquor Suspended Solids
Modified Bardenpho Process
see Phoredox Process. A 5 stage process developed from the original 4 stage or Bardenpho process. The Bardenpho process removed only carbon and nitrogen through anoxic and aerobic zones and the modification which incorporates phosphorus removal by including an anaerobic reactor at the head of the process train. The 5 reaction zones consist of an anaerobic zone, Anoxic zone 1, Aerobic zone, Anoxic zone 2 and a flash aeration zone followed by secondary clarification. Recycles from the clarifier to the head of the plant (return sludge or 's'-recycle) and a mixed liquor denitrification or 'a'-recycle.
Modified Ludzack-Ettinger (MLE) Process
A process train consisting of an anoxic (denitrifying) reactor, an aerobic reactor and secondary clarifier with two recycles, 's'-recycle (sludge or return activated sludge recycle from the clarifier to the anoxic reactor) and an 'a'-recycle (mixed liquor recycle from the aerobic reactor to the anoxic reactor). The plant is intended to remove carbon and nitrogen and is often described as a nutrient removal, D/N or pre-denitrification plant.
Modified University of Cape Town (MUCT) Process
An activated sludge process designed to remove nitrogen and phosphorus biologically, the process optimizes P removal efficiency at the expense of N removal efficiency by introducing a small return sludge denitrification zone as part of the process train. A development based upon the three stage Phoredox process it consists of 4 reaction zones (anaerobic, anoxic 1 (sludge denitrification), anoxic 2 (mixed liquor denitrification) and aerobic followed by a secondary clarifier. Sludge is recycled from the clarifier to anoxic 1 (return sludge or 's' recycle), a recycle from anoxic 1 to the anaerobic zone ('r'-recycle) and a mixed liquor denitrification recycle from the aerobic zone to anoxic 2 ('a'-recycle). The process is named after the research group who developed it.
Molds
Filamentous fungi.
Mole
A mole of any substance is that amount of it which contains the Avogadro Constant number of particles. A mole of any substance is equal to its molecular mass or atomic mass expressed in grams.
Molecule
Two or more atoms chemically bonded to one another.
Monod equation
A mathematical expression first used by Monod in describing the relationship between the microbial growth rate and concentration of growth-limiting substrate.
Most probable number (MPN)
That number of organisms per unit volume that, in accordance with statistical theory, would be more likely than any other number to yield the observed test result or would yield the observed test result with the greatest frequency. Expressed as density of organisms/100 mL. Commonly used for coliform bacteria.
Motility
The property of movement of a cell under its own power.
Mutagen
An agent that induces mutation, such as radiation or certain chemicals.
Mutant
A strain differing from its parent because of mutation.
Mutation
An inheritable change in the base sequence of the genome of an organism.
Negative staining
Some bacteria are easy to stain due to the fuzzy EPS around the cell. One alternative is to stain the background so that the cell (and its EPS slimes) can be more easily viewed microscopically.
Neisser stain
A stain made up of several parts which can detect the presence of intracellular bacterial polyphosphate granules or volutins e.g. Microthrix parvicella. Some bacterial filament trichomes stain uniformly e.g Type 0092.
Nematode
Member of the phylum Nematoda, which is an elongated cylindrical worm parasitic in animals and plants or free living in soil or water.
Nephelometer
An instrument for comparing turbidities of solutions by passing a beam of light through a transparent tube and measuring the ratio of the intensity of the shattered light to that of the incident light.
Neutralization
Decreasing the acidity or alkalinity of a substance by adding to it alkaline or acidic materials, respectively.
Niche
Functional role of a given organism within its habitat
Nitrate
A compound containing nitrogen which can exist in the atmosphere or as a dissolved gas in water and which can have harmful effects on humans and animals.
Nitrate reduction (biological)
Process whereby nitrate is reduced by plants and microorganisms to ammonium for cell synthesis (nitrate assimilation, assimilatory nitrate reduction) or to various lower oxidation states (N2, N2O, NO,) by bacteria using nitrate as the terminal electron acceptor in anaerobic respiration.
Nitrification
The microbiological conversion of ammonia to nitrate.
Nitrification
The conversion of the ammonium ion, NH4+, into the nitrate ion, NO3-. It occurs in two steps:
(i) 2NH4+ + 3O2 → 2NO2- + 2H2O + 4H+ by the bacteria genus
Nitrosomonas
(ii) 2NO2- + O2 → 2NO3- by the bacteria genus Nitrobacter.
Nitrifying bacteria
Autotrophic bacteria capable of oxidizing nitrogenous material.
Nitrite (NO2-)
An intermediate oxygenated form of nitrogen.
Nitrobacter
A genus of bacteria that oxidizes nitrite to nitrate, an autotroph.
Nitrogen (N)
An essential nutrient that is often present in wastewater as ammonia, nitrate, nitrite, and organic nitrogen. The concentrations of each form and the sum (total nitrogen) are expressed as milligrams per liter (mg/L) elemental nitrogen. Also present in some groundwater as nitrate and in some polluted groundwater in other forms. See nutrient.
Nitrogen cycle
A graphical presentation of the conservation of matter in nature showing the chemical transformation of nitrogen through various stages of decomposition and assimilation. The various chemical forms of nitrogen as it moves among living and nonliving matter are used to illustrate general biological principles that are applicable to wastewater and sludge treatment.
Nitrogen, Ammonia (NH3-N)
A measure of the amount of nitrogen which is in the form of ammonia. Expressed in mg/L as N.
Nitrogen, Nitrate (N03--N)
A measure of the amount of nitrogen which is in the form of nitrate. Expressed in mg/L as N.
Nitrogen Removal
Unit operations and unit processes required to remove different forms of nitrogen from a water. This may be accomplished partially in a biological process used in secondary treatment; however, normally it entails subsequent aerobic and anaerobic processes, ammonia stripping, chlorination or other similar steps.
Nitrogenous oxygen demand
A quantitative measure of the amount of oxygen required for the biological oxidation of nitrogenous material, such as ammonia nitrogen and organic nitrogen, in wastewater; typically measured after the carbonaceous oxygen demand has been satisfied. See biochemical oxygen demand, nitrification, second-stage BOD.
Nitrogen fixation
Reduction of nitrogen gas to ammonia by the enzyme nitrogenase.
Nitrogenous Wastes
Animal or vegetable residues that contain significant amounts of nitrogen.
Nitrosomonas
A genus of bacteria that oxidize ammonia to nitrate, an autotroph.
Nocardia
Irregularly bent, short filamentous organisms that are characterized in an activated sludge system when a stiff dark brown foam is present.
Nocardia pinensis-PTLO
Also known as Skermania pinensis and PTLO (Pine-tree-like-organism). Commonly found in foams and is probably included with Nocardia spp. but its distinctive morphology makes it one of the few organisms which can be positively identified from its morphology. Characteristic tree-like branching, Gram positive.
Non-Point Source
Pollution sources which are diffused and do not have a single point of origin or are not introduced into a receiving stream from a specific outlet.
Nonpolar
Possessing hydrophobic (water repelling) characteristics and not easily dissolved in water.
Nonsettleable solids
Suspended matter that will stay in suspension for an extended period of time (such a period may be arbitrarily taken for testing purposes as 1 hour). See suspended solids.
Nostocoida limicola I, II and III
These organisms have been studied extensively and while they have been assumed to be closely related, this has been found not to be so. Nostocoida limicola II is the most common and occasionally dominates. Often found in underloaded plants and controlled by anoxic selectors.
NOx
A general formula referring to any of the nitrogen oxides (for example, nitrous oxide - N2O)
Nozzle aerator
An aerator consisting of a pressure nozzle through which water is propelled into the air in a fine spray. Also called spray aerator.
Nucleus
A membrane-enclosed structure in eukaryotes containillg the genetic material (DNA) organized in chromosomes.
Nutrient
A substance taken by a cell from its environment and used in catabolic or anabolic reactions.
Nutrient deficiency
In wastewater treatment, a condition in which the influent is lacking in an essential nutrient, typically nitrogen, phosphorus, or iron, which limits the growth of the biomass. Chemicals must be added to correct the deficiency before proper treatment can occur.
Nutrient removal
Tertiary treatment introduced to remove some of the trace compounds and elements contained in most domestic wastewaters, e.g. inorganic ammonia, nitrates, phosphates and sulfates, which are little affected by conventional treatment processes.
Obligate
A qualifying adjective referring to an environmental factor always required for growth (for example, "obligate anaerobe").
Oil and grease
In wastewater, a group of substances, including fats, waxes, free fatty acids, calcium and magnesium soaps, mineral oils, and certain other nonfatty materials that are insoluble and can be removed by natural flotation skimming.
Oligonucleotide
Short nucleic acid chain, either obtained from an organism or synthesized chemically.
Oligotroph
An organism preferring habitats which are growth limiting in their nutrient supply (of having a very low concentration of nutrient for growth).
Organelle
A membrane-enclosed structure found in eukaryotic cells.
Organic
Volatile, combustible, and sometimes biodegradable chemical compounds containing carbon atoms with other elements. See inorganic.
Organic compounds
Compounds containing carbon, and derived from or showing the properties of a living organism.
Organic loading
The amount of organic material, typically measured as BOD, applied to a given treatment process. Expressed as weight per unit time per unit surface area or per unit weight.
Organic matter
Carbonaceous waste contained in plant or animal matter and originating from domestic or industrial sources.
Organic nitrogen
Nitrogen chemically bound in organic molecules such as proteins, amines, and amino acids.
Organotroph
Organism that obtains reducing equivalents (stored electrons) from organic substrates.
Osmosis
Diffusion of water through a membrane from a region of low solute concentration to one of higher concentration.
Outfall
(1) The point, location, or structure where wastewater or drainage discharges from a sewer, drain, or other conduit.
(2) The conduit leading to the ultimate disposal area.
Overflow rate
The rate at which water is drawn off from the surface of primary and secondary clarification tanks. It is an important tank design parameter and is derived from the analysis of settling particles. One of the criteria in the design of settling tanks for treatment plants; expressed as the settling velocity of particles that are removed in an ideal basin if they enter at the surface. It is expressed as a volume of flow per unit water surface area.
Oxic
Containing oxygen; aerobic. Usually used in reference to a microbial habitat.
Oxidation
(1) A process by which a compound gives up electrons (or H atoms) and becomes oxidized.
(2) A chemical reaction in which the oxidation number (valence) of an element increases because of the loss of one or more electrons by that element. Oxidation of an element is accompanied by simultaneous reduction of the other reactant. See reduction.
(3) The conversion or organic materials to simpler, more stable forms with the release of energy. This may be accomplished by chemical or biological means.
(4) The addition of oxygen to a compound.
Oxidation ditch
A ring-shaped channel, 11.5 m deep, around which wastewater circulates at 0.3-0.6 ms-1, is aerated by mechanical rotors and undergoes biological treatment by the resident microbes.
Oxidation-reduction (redox) reaction
A pair of rcactions in WiliCh onc colllpound bccomes oxidizcd whilc anotller becomcs reduced and taLcs up the clectrons rcleased in thc oxidation reaction.
Oxidation-reduction potential (ORP)
The potential required to transfer electrons from the oxidant to the reductant and used as a qualitative measure of the state of oxidation in wastewater treatment systems.
Oxidative (electron transport) phosphorylation
The non-phototrophic production of ATP at the expense of a proton motive force formed by electron transport.
Oxidation number
The charge which an atom of an element has, or appears to have, in a compound, e.g. chlorine has an oxidation number of 1.
Oxidation Ponds or Lagoons
Holding ponds designed to allow the decomposition or organic wastes by aerobic or anaerobic means.
Oxidation process
Any method of wastewater treatment for the oxidation of the putrescible organic matter.
Oxygenic photosynthesis
Use of light encrgy to syntllesize ATP and NADPH by nollcyclic photophospllorylation with the production of O2 from water.
Oxygen (O2)
An essential chemical element typically found as O2 and used in biological oxidation. It constitutes approximately 20 percent of the atmosphere.
Oxygen consumed
A measure of the oxygen consuming capability of inorganic and organic matter present in water or wastewater. See chemical oxygen demand.
Oxygen deficiency
The additional quantity of oxygen required to satisfy the oxygen requirement in a given liquid. Typically expressed in milligrams per liter (mg/L).
Oxygen transfer
(1) Exchange of oxygen between a gaseous and a liquid phase.
(2) The amount of oxygen absorbed by a liquid compared to the amount fed into the liquid through an aeration or oxygenation device.
Oxygen sag curve
The longitudinal profile of oxygen concentration in a river.
Oxygen uptake rate
The oxygen used during biochemical oxidation, typically expressed as milligrams O2 per liter per hour in the activated-sludge process.
Oxygen utilization
(1) The portion of oxygen effectively used to support aerobic treatment processes.
(2) The oxygen used to support combustion in the degradation of sludge by incineration or wet air oxidation.
Oxygenation capacity
In treatment processes, a measure of the ability of an aerator to supply oxygen to a liquid.
Ozone
A triatomic gas, particularly prevalent in the stratosphere, formed by the reaction:
O + O2 + energy ⇒ O3 + energy.
Ozone-depleting gases
Gases (e.g. oxides of nitrogen, chlorine, halocarbons and water vapor) which cause destruction of the ozone layer, thereby allowing increased amounts of sunlight to reach the earth.
Packaged treatment plant
Prefabricated units built to an acceptable engineering standard for treating domestic sewage using the extended aeration process.
Partial pressure
The pressure a single gas within a contained mixture of gases would exert if it were the only gas in the container.
Particulates
Suspended material in water or other fluid, may be inorganic and/or organic in nature. May contain living microorganisms and be colloidal in structure (biocolloid).
Parts per million (ppm)
The number of weight or volume units of a minor constituent present with each 1 million units of a solution or mixture. The more specific term milligrams per liter (mg/L), is preferred.
Pasteurization
The process of applying heat to a sufficient extent to retard or destroy a recognized nuisance microbial population. Usually involves the application of heat to a minimum of 40 °C above the ambient temperature for the system.
Pathogen
An agent such as a virus, bacterium or fungus that can cause disease in humans. Pathogens can be present in sewage or effluent discharges, industrial discharges, and non-point discharges such as stormwater runoff.
Peak
(1) The maximum quantity that occurs over a relatively short period. Also called peak demand, peak load.
(2) The highest load carried by an electric generating system during any specific period.
Peak load
(1) The maximum demand for water placed on a pumping station, treatment plant, or distribution system; expressed as a rate.
(2) The maximum rate of flow of wastewater to a pumping station or treatment plant. Also called peak demand.
Peak Wet Weather Flow (PWWF)
The peak volume of sewage produced in wet weather. The design criteria is expressed typically as PWWF = "N"xADWF where N is a whole number multiplier such as 4.
Peptidoglycan
The rigid layer of the cell walls of Bacteria, a thill sheet composed of N-acetylglucosamine, N-acetyl-muramic acid, and a few amino acids. Also called murein.
Percentiles
The first value in a sample set which exceeds exactly x% of the population expressed as x%ile (eg. 95 percentile or 95%ile). The 50 percentile is called the median.
Periplasmic space
The area between the cytoplasmic membrane and the outer membrane in gram negative Bacteria.
Peritrichous flagellation
Condition of having flagella attached to many places on the cell surface.
pH
The degree of acidity or alkalinity of a solution, a measure of the acidity or basicity of a solution i.e. the negative of the logarithm of the hydrogen ion concentration pH = -log10[H+], where [H+] is the concentration of hydrogen ions (M). On the pH scale (0 to 14), a value of 7 at 25 degrees Celsius represents a neutral condition. Decreasing values indicate increasing hydrogen ion concentration (acidity); increasing values indicate decreasing hydrogen ion concentration (alkalinity).
Phenotype
Observable properties of an organism.
Phospholipid
Lipids containing a substituted phosphate group and two fatty acid chains on a glycerol backbone.
Phosphate
A salt or ester of phosphoric acid. See orthophosphate, phosphorus.
Phosphorus
An essential chemical element and nutrient for all life forms. Occurs in orthophosphate, pyrophosphate, tripolyphosphate, and organic phosphate forms. Each of these forms and their sum (total phosphorus) is expressed as milligrams per liter (mg/L) elemental phosphorus. See nutrient.
Phosphorus Removal
The process of removing phosphorus from the wastewater by precipitation, adsorption or biological means.
Photoautotroph
An organism able to use light as its sole source of energy and CO2 as its sole carbon source.
Photoheterotroph
An organism using light as a source of energy and organic materials as carbon source.
Photophosphorylation
Synthesis of high energy phosphate bonds as ATP, using light energy.
Photosynthesis
The use of light energy to drive the incorporation of CO2 into cell material.
Photosynthetic bacteria
Bacteria that obtain their energy for growth from light by photosynthesis.
Phototroph
An organism that obtains energy from light.
Phylogeny
The ordering of species into higher taxa and the construction of evolutionary trees based on evolutionary (natural) relationships.
Physical analysis
The examination of water and wastewater to determine physical characteristics such as temperature, turbidity, color, odors, and taste.
Physical treatment
Any treatment process involving only physical means of solid-liquid separation (for example, screens, racks, clarification, comminutors) whereby chemical and biological reactions do not play an important role in treatment.
Physical-Chemical Treatment
Processes generally used in large-scale wastewater treatment facilities such as air-stripping or filtration (physical), chlorination, or ozone addition (chemical).
Pilus
A fimbria-like structure that is present on fertile cells, both Hfr and F+, and is involved in DNA transfer during conjugation. Sometimes called a sex pilus. See also Fimbria.
Plant hydraulic capacity
The level of flow into a plant above which the system is hydraulically overloaded.
Plug flow
Flow in which fluid particles are discharged from a tank or pipe in the same order in which they entered the tank. The particles retain their discrete identifies and remain in the tank for a time equal to the theoretical detention time.
Plug-flow reactors
Reactors that are not mixed and, therefore, exhibit a concentration gradient along their length.
Polar
Possessing hydrophilic characteristics and generally water soluble.
Pollution
Any direct or indirect alteration of the physical, chemical, thermal, biological or radioactive properties of any part of the environment by discharging, emitting or depositing wastes or substances that adversely affect beneficial use, or that cause a condition that is hazardous or potentially hazardous to public health, safety or welfare or the condition of flora and fauna.
Polyelectrolyte flocculants
Polymeric organic compounds used to induce or enhance the flocculation of suspended and colloidal solids and thereby facilitate sedimentation or the dewatering of sludges. See polymers.
Polyelectrolytes
Complex polymeric compounds, typically composed of synthetic macromolecules that form charged species (ions) in solution. Insoluble polyelectrolytes are used as ion exchange resins. See polymers.
Polymer
A large molecule formed by polymerization of monomeric units. Synthetic organic compounds with high molecular weights and composed of repeating chemical units (monomers). Polymers may be polyelectrolytes (such as water-soluble flocculants or water-insoluble ion-exchange resins) or insoluble uncharged materials, such as those used for plastic or plastic-lined pipe and plastic trickling filter media. Liquid polymers are used as flocculation aids.
Polymerase chain reaction (PCR)
Method for amplifying DNA in vitro , involving the use of oligonucleotide primers complementary to nucleotide sequences in target genes and the copying of the target sequences by the action of DNA polymerase
Polysaccharide
A polymer made up simple sugars. Many polysaccharides are large molecules (macromolecules) made up of many millions of single sugar units.
Pond
An engineered impoundment containing raw or partially treated wastewater in which aerobic and/or anaerobic stabilization occurs. Sometimes referred to as a lagoon.
Precipitation
The depth of rainfall plus the water equivalent of snow, sleet and hail falling during a given measurement period.
Precipitation reaction
A physical or chemical reaction which results in the precipitation of one of the products formed.
Predation
Relationship between two organisms whereby one organism (predator) engulfs or captures and digests the second organism (prey).
Pretreatment
Wastewater treatment which involves removal of gross solids and some readily settleable solids. Processes used to reduce, eliminate, or alter the nature of wastewater pollutants from non-domestic sources before they are discharged into publicly owned treatment works.
Primary treatment
Wastewater treatment which involves sedimentation followed by sludge removal and sludge disposal. The treatment of sewage to a stage where the settleable pollutants are removed by physical means (usually gravity sedimentation).
Primary sedimentation tank
A primary treatment process. It is a gravity sedimentation tank in which the majority of settlable solids are removed from the crude sewage flowing through it. It is placed before the secondary (biological) treatment processes.
Primary Waste Treatment
First steps in wastewater treatment; screens and sedimentation tanks are used to remove most materials that float or will settle. Primary treatment results in the removal of about 30 percent of carbonaceous biochemical oxygen demand from domestic sewage.
Primer
A molecule (usually a polynucleotide) to which DNA polymerase can attach the first deoxyribonucleotide during DNA replication.
Prokaryote
A cell or organism lacking a nucleus and other membrane-enclosed organelles, usually having its DNA in a single circular molecule.
Prostheca
A cytoplasmic extrusion from a cell such as a bud, hypha, or stalk. Protein A polymeric molecule consisting of one or more polypeptides.
Protista
Old taxonomic term referring to algae, fungi, and protozoa (collectively, the eukaryotic protists), and the prokaryotes. The microbial kingdom to which unicellular or cell groups of eucaryotic organisms which lack true tissues, e.g. protozoa, belong.
Proton motive force (PMF)
The force derived from an electrochemical gradient of protons and a membrane potential, thought to drive ATP synthesis and other energy-requiring cell processes. An energized state of a membrane created by expulsion of protons usually occurring through action of an electron transport chain.
Protoplasm
The complete cellular contents, cytoplasmic membrane, cytoplasm, and nuclerus/nucleoid. Term once used to describe the living material of cells. The term has largely been replaced by the term cytoplasm; the latter, however, does not include the cell nucleus. Protoplasm is also used to describe the contents of the hyphae (tubelike structures) of which fungi are composed.
Protozoa
Unicellular eukaryotic microorganisms that lack cell walls. Protozoa Aquatic, free-living and parasitic organisms, these are the most basic of all animals, with only one single cell and measuring no more than 5 1000 μm in size.
Psychropllile
An organism able to grow at low temperatures and showing a growth temperature optimum of less than 15°C
Psychrophilic temperatures
Those in the range 0 10°C.
Psychrotolerant
Able to grow at low temperature but having a growth temperature optimum of less than 15°C.
Pure culture
A culture containing a single kind of micmorganism.
Putrefaction
Biological decomposition, typically of organic matter, with the production of foul-smelling products associated with anaerobic conditions.
Putrescibility
(1) The relative tendency of organic matter to undergo decomposition in the absence of oxygen.
(2) The susceptibility of wastewaters, effluent, or sludge to putrefaction.
(3) The stability of a polluted, raw, or partially treated wastewater.
Quality
The degree to which the project and its components meet the owner's expectations, objectives, standards, and intended purpose; determined by measuring conformity of the project to the plans, specifications, and applicable standards.
Quality Assurance/Quality Control
A system of procedures, checks, audits, and corrective actions to ensure that all EPA research design and performance, environmental monitoring and sampling, and other technical and reporting activities are of the highest achievable quality.
Quality management
The process of planning, organization, implementation, monitoring and documenting of a system of policies and
procedures that coordinate and direct relevant project resources and activities in a manner that will achieve
quality. See Quality.
Quantitative analysis
Chemical determination of the amounts or proportions of constituents in a substance
Raw sludge
Settled sludge promptly removed from sedimentation tanks before significant decomposition has occurred.
Raw wastewater
Wastewater before it receives any treatment.
Reaction rate
The rate at which a chemical reaction progresses. See kinetics.
Reactor
The container, vessel, or tank in which a chemical or biological reaction occurs.
Recalcitrant
A chemical (molecule) which does not degrade, is stable and does persist within a treatment system or the environment. Resistant to microbial attack.
Receiving Waters
A river, lake, ocean, stream, or other watercourse into which wastewater or treated effluent is discharged.
Redox
See Oxidation-reduction reaction
Redox potential
An electrochemical measure (in volts) which for any substance existing in an oxidised or reduced form, gives its affinity for electrons relative to hydrogen under standardised conditions. Negative redox potential indicates a strong reducing agent, and positive redox potential a strong oxidising agent. In wastewater treatment processes a redox potentoal whic is 100 mV would be aerobic while an anaerobic system would have a strongly negative value.
Reduction
A process by which a compound accepts electrons to become reduced.
Reduction potential (Eo')
The inherent tendency, measured in volts, of a compound to act as an electron donor or an electron acceptor.
Respiration
Catabolic reactions producing ATP in whicl1 either organic or inorganic compounds are primary electron donors and organic or inorganic compounds are ultimate electron acceptors.
Retention time
The length of time a wastewater remains in a clarification tank, an important design parameter in the optimization of settling of suspended solids.
Reticulation
The network of pipes that collects wastewater in residential areas and transports it to a treatment plant.
Return activated sludge
Settled activated sludge from the clarifier which is returned to the aeration tank to ensure an active population of microbes will be mixed with the incoming wastewater.
Reuse
Use of reclaimed water for a beneficial purpose. Examples of reuse applications are as follows:
- Agricultural Reuse
- Environmental Reuse
- Industrial Reuse
- Potable Reuse
- Recreational Reuse
- Residential Reuse
- Urban Reuse
Ribonucleic acid (RNA)
A polymer of nucleotides connected via a phosphate-ribose backbone; involved in protein synthesis or as genetic material of some viruses.
Ribosomal RNA (rRNA)
Type of RNA found in the ribosome; some rRNAs participate actively in the process of protein synthesis.
Ribosome
A cytoplasmic particle composed of ribosomal RNA and protein, which is part of the protein-synthesizing machinery of the cell.
Rotating biological contactor (RBC)
A type of secondary treatment process. It is a unit consisting of a series of closely spaced, parallel discs, mounted on a rotating shaft which is supported just above the surface of the waste water to be treated. Microorganisms grow on the disc surface where aerobic degradation of the
pollutants takes place.
Rotifer
Minute, multicellular aquatic animals with rotating cilia on the head and forked tails. Rotifers help stimulate microfloral activity and decomposition, enhance oxygen penetration, and recycle mineral nutrients.
Sampler
A device used with or without flow measurement to obtain a portion of liquid for analytical purposes.
Sarcadina
A species of amoeba that is found in wastewater. It does not play a significant role in the activated-sludge process other than as a indication of start up or the passing of a toxic influence.
Screw pump
A type of rotary pump in which liquid carried between screw threads and displaced axially. These pumps can be open or the flights may be encased in a cylinder.
Secchi disk
A tool used to measure the clarity of water.
Secondary clarifier
A settling tank following secondary treatment designed to remove part of the suspended matter by gravity. Also called a secondary sedimentation tank.
Secondary effluent
(1) The liquid portion of wastewater leaving secondary treatment.
(2) An effluent that, with some exceptions, contains not more than 30 mg/L each (on a 30-day average basis) BOD and suspended solids.
Secondary sedimentation tank
Part of the secondary treatment process (e.g. biological filters or an activated sludge plant) in which settleable solids or humus resulting from the degradation of pollutants are separated from the effluent.
Secondary treatment
In sewage treatment, either the aerobic or anaerobic decomposition of sewage following the removal of nondegradable objects by primary treatment. Generally, a level of treatment that removes 85 per cent of BOD and suspended solids. Also called biological treatment, referring to the treatment of sewage to a stage where the pollutants (settleable, colloidal and dissolved) are removed biologically by the action of microorganisms.
Sedimentation
The process of subsidence and decomposition of suspended matter or other liquids by gravity. It is typically accomplished by reducing the velocity of the liquid below the point at which it can transport the suspended material. It can be variously classified as discrete, flocculant, hindered, and zone sedimentation. It may be enhanced by coagulation and flocculation. Also called settling.
Sedimentation tanks
Holding areas for wastewater where floating wastes are skimmed off and settled solids are pumped out for disposal.
Selection
Placing organisms under conditions where the growth of those with a particular genotype will be favored.
Septic tank
A primitive type of primary treatment process. It takes the form of a settlement tank in which the sludge is retained for sufficient time for the organic matter to undergo anaerobic decomposition.
Septage
The sludge produced by individual on-site wastewater disposal systems, principally septic tanks.
Sequencing Batch Reactor (SBR)
An activated sludge, sewage treatment process in which biological treatment and settlement of solids are combined in the one reactor. Sewage inflow and effluent outflow occurs intermittently but no coincidentally. Compare Intermittently Decanted Extended Aeration.
Serial dilution
Series of stepwise dilutions (usually in sterile water) performed to reduce the populations of microorganisms in a sample to manageable numbers.
Sessile
Attached or stationary habit, a characteristic of many activated sludge protozoa attached to flocs. Organisms that are attached to a surface either directly or indirectly.
Settleability
The tendency of suspended solids to settle.
Settleability test
A determination of the settleability of solids in a suspension by measuring the volume of solids settled out of a measured volume of sample in a specified interval of time, typically reported in milliliters per liter (mL/L). Also called the Imhoff cone test.
Settleable solids
(1) That matter in wastewater that will not stay in suspension during a preselected settling period but settles to the bottom.
(2) In the Imhoff cone test, the volume of matter that settles to the bottom of the cone in 1 hour.
(3) Suspended solids that can be removed by conventional sedimentation.
Settleometer
A large beaker or cylindrical vessel used to conduct a settleability test.
Settling
The process of subsidence and deposition of suspended matter carried by a liquid. It is typically accomplished by reducing the velocity of the liquid below the point at which it can transport the suspended material. Also called sedimentation.
Settling tank
A rectangular or circular tank in which particle velocities within the liquid are sufficiently reduced to allow the suspended material to be removed from the liquid by gravity settling.
Settling velocity
This is the velocity at which a particle will fall to the bottom of a settling tank and is equal to the surface overflow rate for a rectangular tank.
Sewage
The wastewater from homes, offices, shops and factories. Most sewage comes from domestic sources (for example from washing clothes, dishes and using the toilet and shower). Small amounts of trade wastes may also be present.
Sewage Treatment Plant (STP)
A facility using biological secondary treatment technology which removes fine and dissolved organic matter, and with disinfection to destroy bacteria and viruses.
Sewerage
The pipes and other infrastructure used to convey sewage.
Sheath
Tubular structure formed around a chain of cells or around a bundle of filaments.
Short circuiting
A hydraulic condition occurring in parts of a tank where the time of travel is less than the flow-through time.
Side water depth
The depth of water measured along a vertical exterior wall.
Slimes
(1) Substances of a viscous organic nature, typically formed from microbiological growth, that attach themselves to other objects, forming a coating.
(2) The coating of biomass that accumulates in trickling filters or sand filters and periodically sloughs away to be collected in clarifiers.
Sloughing
The act of a slime, for whatever reasons, breaking up and releasing particles (from the slime) to the water passing over the slime.
Sludge
The accumulation of solids resulting from chemical coagulation, flocculation and sedimentation after water or wastewater treatment. The solids which are removed from wastewater by primary and secondary treatment. Screenings and grit are usually removed separately. See activated sludge and biosolids.
Sludge Age
The parameter used to express the mean cell residence time of any microbial cell in the WHOLE SYSTEM (equals the mean 1/d). In many plants it is difficult to determine the value for sludge age because of practical problems in calculating some of the variables in the equation.
Sludge blanket
Accumulation of sludge hydrodynamically suspended within an enclosed body of water or wastewater.
Sludge blanket depth
Also referred to as depth of blanket and is a measurement of the depth of solids in a vessel. The measurement may be performed using a sonic meter, density meter, or Secchi disk.
Sludge bulking
A phenomenon caused when a large number of filamentous micro-organisms present in the mixed liquor interferes with the compaction of the floc and produces a sludge with a poor settling rate.
Sludge conditioning
Addition of chemicals, polyelectrolytes or heat treatment to improve the rate of dewatering. Treatment of liquid sludge, usually by heat treatment or addition of chemicals, before dewatering to facilitate water removal and enhance drainability.
Sludge density index
A measure of the degree of compaction of a sludge after settling in a graduated container, expressed in milliliters per gram (mL/g). The sludge density index is the reciprocal of the sludge volume index (SVI).
Sludge dewatering
The mechanical unit operation used to reduce the moisture content of sludge to 70 75% and thus ensure that the remaining sludge residue effectively behaves as a solid for handling purposes. The process of removing a part of the water from the sludge to convert to a semisolid form. Methods used include draining, pressing, vaccum filtration, pressure filtration, centrifugation and others. .
Sludge stabilization
The process of destroying or inactivating pathogens. Any treatment including such operations as anaerobic or aerobic digestion which converts sludge to a form which can be disposed of without a detrimental effect on the environment.
Sludge Thickening
Settling, air flotation, centrifugation or similar operations to decrease the water content of the sludge yet maintain it in a fluid form.
Sludge Volume Index (SVI)
A measure of the ability of sludge to settle, coalesce and compact on settlement. The ratio of the volume (in milliliters) of sludge settled from a 1000-mL sample in 30 minutes to the concentration of mixed liquor (in milligrams per liter [mg/L]) multiplied by 1000. The SVI is the reciprocal of the sludge density index.
Sludge Yield (Y)
The quantity of solids left over at the end of the secondary treatment processes, consisting of dead cells, surplus microorganisms, non-biodegradable materials.
Soda Ash
A common name for commercial sodium carbonate (Na2CO3).
Sodium bisulfite (NaHSO3)
A salt used for reducing chlorine residuals. A strong reducing agent; typically found in white powder or granular form in strengths up to 44 percent. At a strength of 38 percent, 1.46 parts sodium bisulfite will consume 1 part of chlorine residual.
Sodium carbonate (Na2CO3)
A salt used in water treatment to increase the alkalinity or pH of water or to neutralize acidity. Also called soda ash.
Sodium hydroxide (NaOH)
A strong caustic chemical used in treatment processes to neutralize acidity, increase alkalinity, or raise the pH value. Also known as caustic soda, sodium hydrate, lye, and white caustic.
Sodium hypochlorite
(NaOCl) A water solution of sodium hydroxide and chlorine in which sodium hypochlorite is the essential ingredient.
Sodium metabisulfite
(Na2S2O5) A cream-colored powder used to consume chlorine residual. 1.34 parts of sodium metabisulfite will consume 1 part of chlorine residual.
Solids inventory
Mass of sludge in the treatment system. Inventory of plant solids should be tracked through the use of mass balance set of calculations.
Solids loading
Amount of solids applied to a treatment process per unit time per unit volume.
Solids retention time (SRT)
The average time of retention of suspended solids in a biological wastewater treatment system. Equals the total weight of suspended solids leaving the system per unit time
Solubility product
The equilibrium constant for a reaction involving aprecipitate and its constituent ions, e.g. for barium sulfate BaSO4 → Ba2+ + SO42-, the solubility product = [Ba2+][SO42-]
Spacial Alternation
See Step Feed.
Sparger
An air diffuser designed to give large bubbles. Used singly or in combination with mechanical aeration devices.
Species
Of prokaryotes, a collection of closely related (>97% 16S rRNA sequence homology and >70% genomic hybridization) strains sufficiently different from all other strains to be recognized as a distinct unit. A subdivision of a genus having members differing from other members of the same genus in minor details.
Specific gravity
The ratio of the mass of a body to the mass of an equal volume of water at a specific temperature.
Specific oxygen uptake rate (SOUR)
A measure of the microbial activity in a biological system expressed in milligrams of oxygen per hour per gram of volatile suspended solids. Also called respiration rate.
Sphaerotilus natans
A sheathed filamentous bacteria which exhibits a characteristic "false" branching. Once, incorrectly thought to be responsible for the majority of filamentous bulking episodes S. natans has now been recognized as only infrequently encountered. Associated with nutrient limitation, the organism is believed to not occur in plants with anoxic zones.
Splitter box
(1) A division box that splits the incoming flow into two or more streams.
(2) A device for splitting and directing discharge from the head box to two separate points of application.
Spray aerator
An aerator consisting of a pressure nozzle through which water is propelled into the air in a fine spray.
Stabilization pond
A quiescent, diked pond in which wastewater undergoes biological treatment under microbial action.
Staged treatment
(1) Any treatment in which similar processes are used in series or stages.
(2) In the activated-sludge process, two or more stages consisting of a clarifying stage and a biological stage, or two biological stages.
(3) In anaerobic digestion, an operation in which sludge is completely mixed in the first tank and pumped to a second tank for separation of the supernatant liquor from the solids.
Stalked ciliates
Small, one-celled organisms possessing cilia that are not motile. They develop at lower prey densities, long solid retention times, and low F:Ms.
Standard Methods
A collection of analytical techniques and descriptions commonly accepted in water and wastewater treatment (i.e., Standard Methods for the Examination of Water and Wastewater) published jointly by the American Public Health Association, the American Water Works Association and the Water Environment Federation.
Stationary phase
The period during the growth cycle of a population in which growth ceases.
Step aeration
A procedure for adding increments of settled wastewater along the line of flow in the aeration tanks of an activated sludge plant.
Step feed
(1) A procedure for adding increments of settled wastewater along the line of flow in biological reactors of an activated-sludge process.
(2) This process type has seen a resurgence over the past decade and is sometimes called spacial alternation. The process is used to improve nitrogen removal efficiency and biomass settling characteristics. The process may include nitrified liquor recycles, described as interpass or intrapass recycles to improve denitrification efficiencies. An interpass recycle involves pumping nitrified liquor from an oxic zone to an anoxic zone of an earlier pass, while an intrapass recycle involves recycling nitrified liquor from the oxic zone of a particular pass to the anoxic zone of the same pass.
Sterilization
Treatment resulting in death of all living organisms and viruses in a material.
Stoichiometric
Pertaining to or involving substances that are in the exact proportions required for a given reaction.
Straggler floc
Large (6 mm or larger) floc particles that have poor settling characteristics.
Substrate
(1) Substances used by organisms in liquid suspension.
(2) The liquor in which activated sludge or other matter is kept in suspension.
(3) The molecule undergoing reaction with an enzyme.
Substrate-level phosphorylation
Synthesis of high-energy phosphate bonds through reaction of inorganic phosphate with an activated (usually) organic substrate.
Suctoreans
Ciliates that are stalked in the adult stage and have rigid tentacles to catch prey.
Sulfur Dioxide (SO2)
A heavy, pungent, colorless, gas used as a reducing agent .
Sulfate-reducing bacteria
Bacteria capable of assimilating oxygen from sulfate compounds and reducing them to sulfides. See sulfur bacteria.
Sulfur bacteria
Bacteria capable of using dissolved sulfur compounds in their growth.
Sulfur cycle
A graphical presentation of the conservation of matter in nature showing the chemical transformation of sulfur through various stages of decomposition and assimilation. Various chemical forms of sulfur as it moves among living and nonliving matter are used to illustrate general biological principles that are applicable to wastewater and sludge treatment. Sequence of transformations undergone by sulfur where it is taken up by living organisms, transformed upon death and decomposition of the organism, and converted ultimately to its original state of oxidation.
Supernatant
The partially purified water, high in suspended solids and ammoniacal nitrogen, which is released during the digestion process and whose quality and amount is dependent on the type and settling quality of the waste and on the digester system efficiency.
Surface overflow rate
A design criterion used for sizing clarifiers. Typically expressed as the flow volume per unit amount of clarifier space.
Surfactant
A surface-active agent that concentrates at interfaces, forms micelles, increases solution, lowers surface tension, increases adsorption, and may decrease flocculation.
Suspended growth
The free-moving, aerobic, microbial culture used in the biological treatment of wastewater by the activated sludge process.
Suspended matter
(1) Solids in suspension in water, wastewater, or effluent.
(2) Solids in suspension that can be readily removed by standard filtering procedures in a laboratory.
Suspended solids
(1) Insoluble solids that either float on the surface of, or are in suspension in, water, wastewater, or other liquid.
(2) Solid organic or inorganic particles (colloidal, dispersed, coagulated, or flocculated) physically held in suspension by agitation or flow.
(3) The quantity of material removed from wastewater in a laboratory test and referred to as nonfilterable residue.
Suspended solids (SS)
The total insoluble material present in the influent and effluent to and from the activated sludge system. It can be quantified by passing a known aliquot through an appropriate filter paper and measuring the dry weight of the filtered material.
Symbiosis
Living together in intimate association of two dissimilar organisms. The interactions between the organisms can be commensal or mutualistic.
Synergism
Association between organisms that is mutually beneficial. Both populations are capable of surviving in their natural environment on their own although, when formed, the association offers mutual advantages.
Syntrophy
Interaction of two or more populations that supply each other's nutritional needs.
Tapered aeration
An aeration system which equalizes the quantity of air supplied to the demand for air exerted by the micro-organisms as the liquor flows through the aeration tank. The method of supplying varying quantities of air into the different parts of a biological reactor in the activated-sludge process, more at the inlet, less near the outlet, in approximate proportion to the oxygen demand of the mixed liquor under aeration.
Taxonomy
The study of scientific classification and nomenclature.
Temperature
(1) The thermal state of a substance with respect to its ability to transmit heat to its environment.
(2) The measure of the thermal state on some arbitrarily chosen numerical scale. See Celsius and Fahrenheit.
Terminal electron acceptor
External oxidant (often oxygen) that accepts the electrons as they exit from the electron transport chain
Tertiary treatment
Processes used to further improve secondary effluent quality prior to discharge or reuse. Such processes include sand filtration, oxidation pond retention, disinfection and the use of wetland filters. A further stage of treating sewage following secondary (biological) treatment processes, usually by filtering the secondary effluent to remove suspended solids. Consequential removal of residual BOD may also occur.
Thermophile
An organism with a growth temperature optimum between 45 and 80°C.
Thiothrix I
Favoured by septicity, low F/M and nutrient deficiency, Thiothrix I can usually be seen to contain highly reactive sulphur granules and the filament may be in the form of rosettes. Often found occurring with Type 021N. Common in USA and Italy, but less important elsewhere. Reported in industrial treatment systems.
Thiothrix II
Similar to Thiothrix I and often not distinguished from it. Thiothrix II is a smaller organism which may form rosettes more commonly that Thiothrix I.
Titration
The determination of a constituent in a known volume of solution by the measured addition of a solution of known strength to completion of the reaction as signaled by observation of an end point
Total coliforms
Coliform organisms are used as indicators of faecal contamination of water. They are Gramnegative non-sporing rod-shaped bacteria capable of aerobic and facultatively anaerobic growth in the presence of bile salts and ferment lactose producing acid and gas within 48 hours at 35 37?C.
Total Dissolved Solids (TDS)
The sum of the inorganic and organic materials dissolved in water. Total Suspended Solids (TSS): The sum of all insoluble particles suspended in a water.
Total Kjeldahl Nitrogen (TKN)
A measure of the total organic nitrogen and ammonia present in a sample. It does not include nitrogen as nitrate or nitrite. It is determined by chemical methods, where the nitrogen is converted to ammonium sulphate. The ammonia is then distilled and collected under alkaline conditions, and quantified either titrimetrically or colorimetrically.
Total organic carbon
The amount of carbon bound in organic compounds in a sample. Because all organic compounds include carbon as the common element, total organic carbon measurements provide a fundamental means of assessing the degree of organic pollution.
Total oxygen demand
A quantitative measure of all oxidizable material in a sample water or wastewater as determined instrumentally by measuring the depletion of oxygen after high-temperature combustion. See chemical oxygen demand, total organic carbon.
Total Phosphorus
The total amount of phosphorus detected in the sample. May be four forms: soluble inorganic phosphorus, SIP; soluble organic phosphorus, SOP; particulate inorganic phosphorus, PIP; and particulate organic phosphorus, POP.
Trichome
Row of cells which have remained attached to one another following successive cell divisions. Trichomes are formed by many cyanobacteria and by species of Beggiatoa.
Trickling filter
A biological treatment device; wastewater is trickled over a bed of stones covered with bacterial growth. The bacteria break down the organic wastes in the sewage and produce cleaner water.
Turbidity
The clarity of water, i.e. a measure of the accumulation of collidal particles, determined by light transmission through the water. An expression of the optical property that causes light to be scattered or absorbed rather than transmitted in straight lines through water. Turbidity is caused by suspended matter such as clay, silt, finely divided organic and inorganic matter, plankton and microscopic organisms and gives the water a "cloudy" appearance.
Turbulent mixing
When a flow of liquid or air becomes large, the streamlines become irregular and parcels of the flowing substance begin to move in a highly irregular path while maintaining a net downstream velocity.
Types - Filamentous Bacteria
One of the main problems associated with filamentous bacteria is that the procedure used for "identification" is based upon morphology, or the physical appearance of the organisms. When these organisms were observed and described many were given type numbers related to the samples in which they were originally found. The names have remained with us as many of these organisms have not been further classified or identified and are only known in biological treatment systems. The list below contains the most important of these types with brief notes on each.
Type 0041
Widely found in activated plants in all countries surveyed, and associated with low F/M and nutrient deficiency (industrial plants such as paper mills). Recognized by its positive Gram stain and attached growth.
Type 0092
An important organism in bulking and foaming plants in many countries, particularly in biological nutrient removal plants. Associated with low F/M plants, Type 0092 is recognized by responding to Neisser stain by a whole trichome staining violet.
Type 021N
Very common in some countries (USA, Japan, Germany) while seldom seen in others (RSA, Australia). Associated with low F/M, septicity and nutrient deficiency. Recognized through its large and often irregular discoid cells, trichomes often form knots and loops.
Type 0411
Infrequently seen, little is known of this relatively featureless organism.
Type 0581
Relatively featureless Gram and Neisser negative filament. Uncommon and rarely dominant, it has been reported as being favoured by low F/M. Superficially similar to Microthrix parvicella except for Gram stain.
Type 0675
Occurs in similar situations to Type 0041 and often with it. Literature suggests that it has smaller cell dimensions than Type 0041, but many groups no longer distinguish between them.
Type 0803
A significant filament in activated sludge plants. Described as Gram and Neisser negative parallel bundles of filaments with few distinguishing features. Often mistaken for Type 0914.
Type 0914
Common, but not usually dominant filament in bulking and foaming BNR plants in the RSA and Australia. Associated with long MCRT, 0914 appears in irregular bundles.
Type 0961
Commonly seen in low F/M plants world-wide. Filaments appear empty or drinking straw-like with sharply angled bends, Gram and Neisser negative.
Type 1701
Most commonly observed in the northern hemisphere, where it is a major filament. Associated with low DO, it has been reported in bulking sludges and foams. This Gram and Neisser negative filament is sheathed and usually has attached growths.
Type 1702
Rarely seen, little is known about the characteristics or occurrence of this Gram and Neisser negative organism.
Type 1851
Incidental filament in BNR plants in the RSA and Australia. Associated with long MCRT.
Type 1852
Not commonly found or reported, has few features making identification difficult. Consequently little is known about this organism
Type 1863
Not commonly found in plants, but occasionally dominates in bulking plants. Associated with high F/M and short MCRT. Recognized by its resemblence to a string of beads.
Ultimate biochemical oxygen demand
(1) Commonly, the total quantity of oxygen required to completely satisfy the first-stage BOD.
(2) More strictly, the quantity of oxygen required to completely satisfy both the first- and second-stage BODs.
Ultrasonic sensor
A device that transmits and then receives ultrasonic waves that bounce off a liquid surface to measure the liquid level. The elapsed time for the signal to leave and return to the sensor is a function of the distance to the liquid surface.
Ultrafiltration
Filtration technique used in water treatment to separate out bacteria larger than 1 - 100 µm.
Underdrain
A drain that carries away groundwater or the drainage from prepared beds to which water or wastewater has been applied.
University of Cape Town (UCT) Process
An activated sludge process designed to remove nitrogen and phosphorus biologically, the process optimizes P removal efficiency at the expense of N removal efficiency by recycling return sludge to the anoxic or denitrification zone. A development based upon the three stage Phoredox process it consists of 3 reaction zones (anaerobic, anoxic (sludge and mixed liquor denitrification) and aerobic followed by a secondary clarifier. Sludge is recycled from the clarifier to the anoxic (return sludge or 's' recycle), a recycle from the anoxic to the anaerobic zone ('r'-recycle) and a mixed liquor denitrification recycle from the aerobic zone to the anoxic ('a'-recycle). The process is named after the research group who developed it. This process has been partly superceded by the Modified University of Cape Town (MUCT) Process which has been reported to be more easily controlled and optimized.
Upflow
Term used to describe treatment units in which flow enters at the bottom and exits at the top.
Upflow clarifier
A treatment unit in which liquid containing suspended solids is passed upward through a blanket of settling sludge. Mixing, flocculation, and solids removal are all accomplished in the same unit.
Upflow coagulation
Coagulation achieved by passing liquid, to which coagulating chemicals may have been added, upward through a blanket of settling sludge.
Upflow tank
(1) A sedimentation tank in which water or wastewater enters near the bottom and rises vertically, typically through a blanket of previously settled solids. The clarified liquid flows out at the top and settled sludge flows out the bottom.
(2) A vertical-flow tank.
Upflow column
Where the water/wastewater flows upward under pressure througha column or tank, instead of downward by gravity. When used in waterfiltration, it is akin to the backwashing process in rapid gravity filters. Also used in aerobic digestion of industrial wastewaters where the column ispacked with aggregate or synthetic material.
Vacuole
A small space in a cell that contains fluid and is surrounded by a membrane. In contrast to a vesicle, a vacuole is not rigid.
Viable
Alive; able to reproduce.
Viable count
Measurement of the concentration of live cells in a microbial population.
VIP (Virginia Initiative Process)
Essentially a variant of the University of Cape Town (UCT) process and often described as UCT/VIP. The only essential difference between the VIP and the UCT is the generally lower sludge ages used in operating the process. Consequently the processes have little to differentiate them.
Virion
A virus particle; the virus nucleic acid surrounded by a protein coat and in some cases other material.
Virus
A genetic element containing either DNA or RNA that replicates in cells but is characterized by having an extracellular state.
Volatile acid
A fatty acid with, at most, six carbon atoms which are water soluble.
Volatile solids
Solids, frequently organic, which volatilize at a temperature of 550÷C. Solids, dissolved or suspended, which are primarily organic and exert the significant portion of the BOD during stabilization. Expressed in mg/L.
Waste Activated Sludge (WAS)
Excess activated sludge removed from the treatment process to maintain the micro-organism population in balance with the sewage inflow.
Wastewater
Water which has been used, at least once, and has thereby been rendered unsuitable for reuse for that purpose without treatment and which is collected and transported through sewers. Wastewater normally includes water from both domestic and industrial sources.
Wastewater Characterization
A complex fractionation of an influent wastewater which usually divides COD and TKN into subsets. Usually used in activated sludge process modelling.
Wastewater Inventory
A detailed listing of all wastewater sources including data on flow, temperature, BOD, suspended solids and other parameters necessary to define quality.
Wuhrmann Process
Developed in the 1960's, this process was a post denitrification process using an unaerated zone after the aeration basin of a conventional activated sludge plant. Denitrification was inefficient due to the low (endogenous) denitrification rate. This plant has become the basis for some plants using external carbon (methanol) addition to manage denitrification.
Xenobiotic
A chemical compound which does not occur naturally, but is completely synthetic.
Yeasts
Unicellular fungi
Zone settling
Particles are so close together that interparticle forces
hinder the settling of neighbouring particles, causing all the particles to
remain in a fixed position relative to each other and to settle at a
constant velocity.
Zoogleal bulking
Also called slime bulking, non-filamentous bulking, this phenomenon is caused by the accumulation of excessive amounts of bacterial exopolysaccharide (EPS) in the sludge. Zone settling and compression of the afflicted sludges are degraded.
Zoogleal matrix
The floc formed primarily by slime-producing bacteria in the activated sludge process or in filter beds.
Zoogleal slime
A jelly-like matrix developed by certain bacteria. A major part of activated sludge floc and of trickling filter slimes.
Zoogloea
Zoogloea ramigera or Z. ramigera Is an organism which is assumed to have an important floc forming role in activated sludge. Has been observed in a both a fingered form and an amorphous or globular form.
Zooplankton
Plankton that consists of animals, such as protozoans.
Zygote
In eukaryotes, the single diploid cell resulting from
the union of two haploid gametes.
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