Formulas & Glossary


Basic and advanced math formulas for the use in water and waste water operations. 


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ACTIVATED SLUDGE PROCESS - A biological wastewater treatment process which speeds up the decomposition of wastes in the wastewater being treated. Activated sludge is added to wastewater and the mixture (mixed liquor) is aerated and agitated. After some time in the aeration tank, the activated sludge is allowed to settle out by sedimentation and is disposed of (wasted) or reused (returned to the aeration tank) as needed. The remaining wastewater then undergoes more treatment.   

ACUTE HEALTH EFFECT- An adverse effect on a human or animal body, with symptoms developing rapidly

ADSORPTION- The gathering of gas, liquid, or dissolved substance on the surface or interface zone of another material.

ADVANCED WASTE TREATMENT- Ant process of water renovation that upgrades treated wastewater to meet specific reuse requirements. May include general cleanup of water or removal of specific parts of wastes insufficiently removed by conventional treatment processes. Typical processes include chemical treatment and pressure filtration. Also called TERTIARY TREATMENT.

AERATION LIQUOR - The process of adding air to water. In wastewater treatment, air is added to freshen wastewater and to keep solids in suspension. With mixtures of wastewater and activated sludge, adding air provides mixing and oxygen for the microorganisms treating the wastewater.

AERATION TANK- The tank where raw or settled wastewater is mixed with return sludge and aerated. The same as aeration bay, aerator, or reactor.

AEROBES- Bacteria that must have molecular (dissolved) oxygen (DO) to survive. Aerobes are aerobic bacteria.

AEROBIC- A condition in which atmospheric or dissolved molecular oxygen is present in the aquatic (water) environment.

AEROBIC BACTERIA- Bacteria which will live and reproduce only in an environment containing oxygen which is available for their respiration (breathing) namely atmospheric oxygen or oxygen dissolved in water. Oxygen combined chemically, such as in water molecules (H2O), cannot be used for respiration by aerobic bacteria.

AEROBIC DECOMPSITION – The decay or breaking down of organic material in the presence of “free” or dissolved oxygen.

AEROBIC DIGESTION - The breakdown of wastes by microorganisms in the presence of dissolved oxygen. The digestion process may be used to treat only waste activated sludge, or trickling filter sludge and primary (raw) sludge, or waste sludge from activated sludge treatment plants designed without primary settling. The sludge to be treated is placed in a large aerated tank where aerobic microorganisms decompose the organic matter in the sludge. This is an extension of the activated sludge process.

AEROBIC PROCESS- A waste treatment process conducted under aerobic (in the presence of “free” or dissolved oxygen) conditions.

AESTHETIC-Attractive or appealing.

AGGLOMERATION- The growing or coming together of small scattered particles into larger flocs or particles which settle rapidly. Also see FLOC

AIR BINDING- The clogging of a filter, pipe or pump due to the presence of air released from water. Air entering the filter media is harmful to both the filtration and backwash processes. Air can prevent the passage of water during the filtration process and can cause the loss of filter media during the backwash process.

AIR GAP- An open vertical drop, or vertical empty space, between a drinking (potable) water supply and the point of use in a wastewater treatment plant. This gap prevents the contamination of drinking water by backsiphonage because there is no way wastewater can reach the drinking water supply.

Air lift pump- A special type of pump. This devise consists of a vertical riser pipe submerged in the wastewater or sludge to be pumped, Compressed air is injected into a tail piece at the bottom of the pipe. Fine air bubbles mix with the wastewater or sludge to form a mixtures lighter than the surrounding water which causes the mixture to rise in the discharge pipe to the outlet. An air lift pump works like the center stand in a percolator coffee pot.

Air Padding- Pumping dry air into a container to assist with the withdrawal of a liquid or to force a liquefied gas such as chlorine or sulfur dioxide out of a container.

Algae- Microscopic plants which contain chlorophyll and live floating or suspended in water. They also may be attached to structures, rocks, or other submerged surfaces. Algae produce oxygen during the sunlight hours and use oxygen during the night hours. Their biological activities appreciably affect the pH, alkalinity and dissolved oxygen of the water.

Algal- Sudden, massive growths of microscopic and macroscopic plant life, such as green or blue-green algae, which can, under the proper conditions, develop in lakes, reservoirs, and also in ponds.

Aliquot- Representative portion of a sample, Often an equally divided portion of a sample.

Alkali-  Any of certain soluble salts, principally of sodium, potassium, magnesium , and calcium, that have the property of combining with acids to form neutral salts and may be used in chemical processes such as water or wastewater treatment.

Alkalinity- The capacity of water or wastewater to neutralize acids. This capacity is caused by the water’s content of carbonate, bicarbonate, hydroxide, and occasionally borate, silicate, and phosphate. Alkalinity is expressed in milligrams per liter or equivalent calcium carbonate. Alkalinity is not the same as pH because water does not have to be strongly basic to have a high alkalinity. Alkalinity is a measure of how much acid must be added to a liquid to lower the pH to 4.5.

Ambient Temperatures- Temperature of the surroundings

Aerometric- A method of measurement that records electric current flowing or generated, rather than recording voltage. Amperometric titration is a means of measuring concentrations of certain substances in water.

Anaerobes- Bacteria that do not need molecular oxygen to survive

Anaerobic- A condition in which atmospheric or dissolved molecular oxygen is not present in the aquatic environment.

Anaerobic bacteria- Bacteria that live and reproduce in an environment containing no “free” or dissolved oxygen. Anaerobic bacteria obtain their oxygen supply by breaking down chemical compounds which contain oxygen, such as sulfate.

Anaerobic decomposition- The decay or breaking down of organic material in an environment containing no “free” or dissolved oxygen.

Anaerobic digestion- Wastewater solids and water are placed in a large tank where bacteria decompose the solids in the absence of dissolved oxygen. At least two general groups of bacteria act in balance. 1)Saprophytic bacteria break down complex solids to volatile acids, the most common of which are acetic and propionic acids; and 2)Methane Fermenters break down the acids to methane, carbon dioxide and water.

Analog Readout- The readout of an instrument by a pointer against a dial or scale.

Anhydrous- Very dry. No water or dampness is present

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

Anoxic- A condition in which atmospheric or dissolved molecular oxygen is not present in the aquatic environment and nitrate is present. Oxygen deficient or lacking sufficient oxygen. The term is similar to Anaerobic.

Aseptic- Free from the living germs of disease, fermentation, or putrefaction. Sterile.

Aspirate- Use of a hydraulic device to create a negative pressure by forcing a liquid through a restriction, such as a Ventura. An aspirator may be used in the lab in place of a vacuum pump sometimes used instead of a sump pump.

Authority- The power and resources to do a specific job or to get that job done.

Axial to impeller- The direction in which material being pumped flows around the impeller or flows parallel to the impeller shaft.

Axis of impeller- An imaginary line running alone the center of a shaft.

Biochemical Oxygen Demand- The rate at which organisms use the oxygen in water or wastewater while stabilizing decomposable organic matter under aerobic conditions. In decomposition, organic matter serves as food for the bacteria and energy results from its oxidation. BOD measurements are used as a measure of the organic strength of wastes in water.

British Thermal Unit- The amount of the heat required to raise the temperature of one pound of water one degree Fahrenheit.

Bacteria- Bacteria are living organisms, microscopic in size, which usually consist of a single cell. Most bacteria use organic matter for their food and produce waste products as the result of their processes.

Bacterial culture- In the case of activated sludge, the bacterial culture refers to the group of bacteria classified as aerobes and facultative organisms, which covers a wide range of organisms. Most treatment processes in the United States grow facultative organisms which use the carbonaceous BOD. Facultative organisms can live when oxygen resources are low. What “nitrification” is required, the nitrifying organism are OBLIGATE AEROBES and must have at least 0.5 mg/l of dissolved oxygen throughout the whole system to function properly.

Back flow- A reverse flow condition, created by a difference in water pressure, which causes water to flow back into the distribution pipes of a potable water supply from any source or sources other than an intended source.

Backsiphonage- A form of backflow caused by a negative or below atmospheric pressure within a water system

Baffle- A flat board or plate, deflector, guide or similar device constructed or placed in flowing water, wastewater, or slurry system to cause more uniform flow velocities, to absorb energy, and to divert, guide, or agitate liquids

Base- 1. A substance which takes up or accepts protons. 2. A substance which dissociates in aqueous solution to yield hydroxyl ions. 3. A substance containing hydroxyl ions which reacts with an acid to form a salt or which may react with metals to form precipitates.

Batch Process- A treatment process in which a tank or reactor is filled, the wastewater is treated or a chemical solution is prepared, and the tank is emptied, The tank may then be filled and the process repeated, Batch processes are also used to cleanse, stabilize or condition chemical solutions for use in industrial manufacturing and treatment processes.

Bioassay- 1.A way of showing or measuring the effect of biological treatment on a particular substance or waste, or 2.A method of determining the relative toxicity of a test sample of industrial wastes or other wastes by using live test organisms such as fish.

Biochemical Oxygen demand test- A procedure that 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.

Biodegradable- Organic matter that can be broken down by bacteria to more stable forms which will not create a nuisance or give off foul odors is considered biodegradable.

Biodegradation- The breakdown of organic matter by bacteria to more stable forms which will not create a nuisance or give off foul odors.

Bioflocculation- The clumping together of fine, dispersed organic particles by the action of certain bacteria and algae. This results in faster and more complete settling of the organic solids in wastewater.

Biomass- A mass or clump of organic material consisting of living organisms feeding on the wastes in wastewater, dead organism and other debris.

Biomontoring- A term used to describe methods of evaluating or measuring the effects of toxic substances in effluents on aquatic organisms in receiving waters, There are two types of biomonitoring, the biosurvey and the bioassay.

Biosolids- A primarily organic solids product, produced by wastewater treatment processes, that can be beneficially recycled,

Biosurvey- A survey of the types and numbers or organisms naturally present in the receiving waters upstream and downstream from plant effluents. Comparisons are made between the aquatic organism upstream and those organisms downstream of the discharge.

Blank- A bottle containing only dilution water or distills water; the sample being tested is not added, Tests are frequently run on a SAMPLE and a BLANK and the differences are compared, the procedure helps to eliminate or reduce test result errors that could be caused when the dilution water or distilled water used is contaminated

Blinding- The clogging of the filtering medium of a microscreen or a vacuum filter when the holes or spaces in the media become clogged or sealed off due to a buildup of grease or the material being filtered

Bound Water- Water contained within the cell mass of sludge’s or strongly held on the surface of colloidal particles. One of the causes of bulking sludge in the activated sludge process,

Breakout of chlorine- A point at which chlorine leaves solution as a gas because the chlorine feed rate is too high. The solution is saturated and cannot dissolve any more chlorine, the maximum strength a chlorine solution can attain is approximately 3500 mg/l. beyond this concentration molecular chlorine is present which will break out of solution and cause “off-gassing” at the point of application.

Breakpoint Chlorination- Addition of chlorine to water or wastewater until the chlorine demand has been satisfied, At this point, further additions of chlorine result in a residual that is directly proportional to the amount of chlorine added beyond the breakpoint.

Brinelling - Tiny indentations high on the shoulder of the bearing race or bearing. A type of bearing failure.  

Buffer- A solution or liquid whose chemical makeup neutralizes acids or bases without a great change in pH.

Buffer action- The action of certain ions in solution in opposing a change in hydrogen ion concentration.

Buffer Capacity- A measure of the capacity of a solution or liquid to neutralize acids or base. This is a measure of the capacity of water or wastewater for offering a resistance to change in pH.

Buffer solution- A solution containing two or more substances which, in combination, resist any marked change in pH following addition of moderate amounts or either strong acid or base.

Bulking- Clouds of billowing sludge that occur throughout secondary clarifiers and sludge thickeners when the sludge does not settle properly.  In the activated sludge process, bulking is usually caused by filamentous bacteria or bound water.

CFR- Code of Federal Regulations. A publication of the United States Government which contains all of the proposed and finalized federal regulations, including safety and environmental regulations.

Call Date- First date a bond can be paid off

Calorie- The amount of heat required to raise the temperature of one gram of water on degree Celsius.

Carcinogen- Any substance which tends to produce cancer in an organism.

Carbonaceous- A stage of decomposition that occurs in biological treatment processes when aerobic bacteria, using dissolving oxygen, change carbon compounds to carbon dioxide, Sometimes referred to as “first stage BOD” because the microorganisms attack organic or carbon compounds first and nitrogen compounds later.

Cathodic- An electrical system for prevention of rust, corrosion, and pitting of steel and iron surfaces in contact with water, wastewater or soil. A low voltage current is made to flow through a liquid or a soil in contact with the metal in such a manner that the external electromotive force renders the metal structure cathodic, this concentrates corrosion on auxiliary anodic parts which are deliberately allowed to corrode instead of letting the structure corrode.

Cation- A positively charges ion in an electrolyte solution, attracted to the cathode under the influence of a difference in electrical potential. Sodium ion is a cation.

Cation Exchange capacity- The ability of a solid or other solid to exchange cations with a liquid.

Caution- This word warns against potential hazards or cautions against unsafe practices.

Cavitation- The formation and collapse of a gas pocket or bubble on the blade of an impeller or the gate of a valve. The collapse of this gas pocket or bubble drives water into the impeller or gate with a terrific force that can cause pitting on the impeller or gate surface. Cavitation is accompanied by loud noises that sound like someone is pounding on the impeller or gate with a hammer.

Centrate- The water leaving a centrifuge after most of the solids have been removed.

Centrifuge- A mechanical device that uses centrifugal or rotational forces to separate solids from liquids.

Certification Examination- An examination administered by a state agency that operators take to indicate a level of professional competence.

Certified operator- A person who has the education and experience required to operate a specific class of treatment facility as indicated by possessing a certificate of professional competence given by a state agency or professional association.

Chain of custody- A record of each person involved in the handling and possession of a sample from the person who collected the sample to the person who analyzed the sample weight by its valence.

Chemical Equivalent- The weight in grams of a substance that combines with or displaces one gram of hydrogen, Chemical equivalents usually are found by dividing the formula weight by its valence.

Chemical Oxygen Demand- A demand of the oxygen consuming capacity of organic matter present in wastewater. COD is expressed as the amount of oxygen consumed from a chemical oxidant in mg/l during a specific test. Results are not necessarily related to the biochemical oxygen demand because of the chemical oxidant may react with substance that bacteria do not stabilize.

Chloramines- Compounds formed by the reaction of hypochlorous acid with ammonia.

Chlorination- The application of chlorine to water or wastewater, generally for the purpose of disinfection, but frequently for accomplishing other biological or chemical results.

Chlorine contact chamber- A baffled basin that provides sufficient detention time of chlorine contact with wastewater for disinfection to occur. The minimum contact time is usually 30 minutes

Chlorine demand- Chlorine demand is the difference between the amount of chlorine added to wastewater and the amount of residual chlorine remaining after a given contact time. Chlorine demand may change with dosage, time, temperature, pH, and nature and amount of the impurities of the water.

Chlorine requirements- The amount of chlorine which is needed for a particular purpose. Some reasons for adding chlorine are reducing the number of coliform bacteria, obtaining a particular chlorine residual, or oxidizing some substance in the water, in each case a definite dosage of chlorine will be necessary.

Chlorine residual- The concentration of chlorine present in water after the chlorine demand has been satisfied. The concentration is expressed in terms of the total chlorine residual, which includes both the free and combined or chemical bound chlorine residuals.

Chlororganic- Organic compounds combined with chlorine. These compounds generally originate from, or are associated with, living or dead organic materials.

Chronic health Effect- An adverse effect on a human or animal body with symptoms that develop slowly over a long period of time or that recur frequently

Ciliates- A class of protozoan distinguished by short hairs on all or part of their bodies

Clarification- Any process or combination of processes that main purpose of which is to reduce the concentration of suspended matter in a liquid.

Clarifier- Settling tank, sedimentation Basin. A tank or basin in which wastewater is held for a period of time during which the heavier solids settle to the bottom and the lighter materials float to the water surface.

Coagulant Aid- Any chemical or substance used to assist or modify coagulation

Coagulants- Chemical that cause very fine particles to clump together into larger particles. This makes it easier to separate the solids from the water by settling, skimming, draining or filtering.

Coagulation- The clumping together of very fine particulars into larger particles cause by the use of chemicals. The chemicals neutralize the electrical charges of the fine particles, allowing them to cone closer and form larger clumps. This clumping together makes it easier to separate the solids from water by settling, skimming, draining and filtering.

Code of federal regulations- A publication of the United States Government which contains all of the proposed and finalized federal regulations, including environmental regulations.

Coliform- One type of bacteria. The presence of coliform-group bacteria is an indication of possible pathogen bacterial contamination. The human intestinal tract is one of the main habitats of coliform bacteria. They may also be found in the intestinal tracts of warm blooded animals, and in plants, soil, air, and the aquatic environment. Fecal coliforms are those coliform found in the feces of various warm blooded animals

Colloids- Very small, finely divided solids that remain dispersed in a liquid for a long time due to their small size and electrical charge. When most of the particles in the water have a negative electrical charge, they tend to repel each other, this repulsion prevents the particles from clumping together, becoming heavier and settling out.

Colorimetric measurement- A measuring unknown chemical concentrations in water by measuring a samples color intensity. The specific color of the samples, developed by addition of chemical reagents, is measured with a photoelectric colorimeter or is compared with “color standards” using, or corresponding with, known concentrations of the chemical

 Combined Available Chlorine- The total chlorine, present as chloramines or other derivatives, that is present in water and is still available for disinfection and for oxidation or organic matter. The combined chlorine compounds are more stable than free chlorine forms, but they are somewhat slower in disinfection action

Combined available chlorine residual- The concentration of residual chlorine that is combined with ammonia, organic nitrogen, or both in water as a chloramines and yet is still available to oxidize organic matter and help kill bacteria

Combined Chlorine- The sum of the chlorine species composed of free chlorine and ammonia, including monichloramine, dichloramine and trichloramine. Dichloramine is the strongest disinfectant of these chlorine species, but it has less oxidative capacity than free chlorine.

Combined Residual Chlorination- The application of chlorine to water or wastewater to produce a combined available chlorine residual. The residual may consist of chlorine compounds formed by the reaction of chlorine with natural or added ammonia or with certain organic nitrogen compounds

Combined Sewer- A sewer designed to carry both sanitary wastewaters and storm or surface water runoff.

Comminution- Shredding. A mechanical treatment process which cuts large pieces of wastes into smaller pieces so they won’t plug pipes or damage equipment.

Comminutor- A device used to reduce the size of the solid chunks in wastewater by shredding. The shredding action is like many scissors cutting or clopping to shreds all the large influent solids material in the wastewater.

Competent Person- A competent person is defined by OSHA as a person capable of identifying existing and predictable hazards in the surrounding, or working conditions which are unsanitary, hazardous or dangerous to employees, and who has authorization to take prompt correctives measures to eliminate the hazards.

Composite Sample- A composite sample is a collection of individual samples obtained at regular intervals, usually every one or two hours during a 24 hour time span, each individual sample is combined with the others in proportions to the rate of flow when the sample was collected. The resulting mixture forms a representative sample and is analyzed to determine the average conditions during the sampling period.

Compound- A pure substance composed of two or more elements whose composition is constant.

Coning- Development of a cone shaped flow of liquid, like a whirlpool, through sludge. This can occur in a sludge hopper during sludge with drawl when the sludge becomes too thick. Part of the sludge remains in place while the liquid rather than sludge flows out of the hopper.

Contact Stabilization- Contact stabilization is a modification of the conventional activated sludge process. In contact stabilization, two aeration tanks are used. One tank is for separate reaeration of the return sludge for at least four hours before it is permitted to flow into the other aeration tank to be mixed with the primary effluent requiring treatment.

Continuous Process- A treatment process in which water is treated continuously in a tank or reactor. The water being treated continuously flows into the tank at one end, is treated as it flows through the tank, and flows out the opposite and as treated water.

Conventional Treatment- The preliminary treatment, sedimentation, flotation, trickling filter, rotating biological contactor, activated sludge and chlorination wastewater treatment processes.

Coverage Ratio- The coverage ratio is a measure of the ability of the utility to pay the principal and interest on loans and bonds in addition to any unexpected expenses.

Cross Connection- A connection between a drinking water system and an unapproved water supply.

Cryogenic- Very low temperature, Associated with liquefied gases

Dissolved Oxygen (DO) - The molecular oxygen dissolved in water or wastewater

DPD Method- A method of measuring the chlorine residual in water. The residual may be determined by either titrating or comparing a developed color with color standards.

Danger- The word danger is used where an immediate hazard presents a threat of death or serious injury to employees.

Dangerous Air Contamination- An atmosphere presenting a threat of causing death, injury, acute illness, or disablement due to the presence of flammable and/or explosive, toxic or otherwise injurious or incapacitating substance.

Dateometer- A small calendar disc attached to motors and equipment to indicate the year in which the last maintenance service was preformed

Debt Service- The amount of money required annually to pay the 1. Interest on outstanding debts; 2. Funds due on a maturing bonded debt or the redemption of bonds

Dechlorination- The removal of chlorine from the effluent of a treatment plant. Chlorine needs to be removed because chlorine is toxic to fish and other aquatic life.

Decibel- A unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for the average level at which sound causes pain to humans.

Decomposition, Decay- Process that convert unstable materials into more stable forms by chemical or biological action. Waste treatment encourages decay in a controlled situation so that material may be disposed of in a stable form. When organic matter decays under anaerobic conditions, undesirable odors are produced. The aerobic processes in common use for wastewater treatment produce much less objectionable odors.

Degradation- The conversion or breakdown of a substance to simpler compounds, For example, the degradation of organic matter to carbon dioxide and water.

Delegation- The act in which power is given to another person in the organization to accomplish a specific job.

Denitrification- 1. The anoxic biological reduction of nitrate nitrogen to nitrogen gas, 2. The removal of some nitrogen from a system, 3. An anoxic process that occurs when nitrite or nitrate ions are reduced to nitrogen gas and nitrogen bubbles are formed as a result of this process. The bubble attach to the biological floc in the activated sludge process and float the floc to the surface of the secondary clarifiers. This condition is often the cause of rising sludge observed in secondary clarifiers or gravity thickeners.

Density- A measure of how heavy a substance is for its size, Density is expressed in terms of weight per unit volume, that is, grams per cubic centimeter or pounds per cubic foot. The density of water is 1.0 gram per cubic centimeter or about 62.4 pound per cubic foot.

Desiccator- A closed container into which heated weighing or drying dishes are placed to cool in a dry environment in preparation for weighing. The dishes may be empty or they may contain a sample. Desiccators contain a substance, such as anhydrous calcium chloride, which absorbs moisture and keeps the relative humidity near zero so that the dish or sample will not gain weight from absorbed moisture.

Detention Time- The time required to fill a tank at a given flow or the theoretical time required for a given flow of wastewater to pass through a tank.

Detritus- The heavy, coarse mixture of grit and organic material carried by wastewater

Dew Point- The temperature to which air with a given quantity of water vapor must be cooled to cause condensation of the vapor in the air.

Dewater- 1. To remove or separate a portion of the water present on a sludge or slurry. To dry sludge so it can be handled and disposed of, 2. To remove or drain the water from a tank or trench.

Dewaterable- This is a property of sludge related to the ability to spate the liquid portion from the solid, with or without chemical conditioning. A material is considered dewaterable if water will readily drain from it.

Diaphragm Pump- A pump in which a flexible diaphragm, generally of rubber or equally flexible material, is the operating part. It is fastened at the edges in a vertical cylinder. When the diaphragm is raised suction is exerted, and when it is depressed, the liquid is forced through a discharge valve.

Diffused Air Aeration- A diffused are activated sludge plant takes air, compresses it, and then discharges the air below the water surface of the aerator through some type of air diffusion device.

Diffuser- A device used to break the air stream from the blower system into fine bubble in an aeration tank or reactor.

Digester- A tank in which sludge is placed to allow decomposition by microorganisms. Digestion may occur under anaerobic or aerobic conditions.

Digital Readout- The use of number to indicate the value or measurement of a variable. The readout of an instrument by a direct, numerical reading of the measured value. The signal sent to such readouts usually an analog signal.

Discharge Head- The pressure measured at the centerline of a pump discharge and very close to the discharge flange, converted into feet, the pressure is measured from the centerline of the pump to the hydraulic grade line of the water in the discharge pipe.

                Discharge Head, ft = (Discharge Pressure, psi)(2.31 ft/psi)

Disinfection- The process designed to kill or inactivate most microorganisms in wastewater, including essentially all pathogenic bacteria. There are several ways to disinfect, with chlorination being the most frequently used in wastewater or water treatment plants.

GIS- Geographic Information System. A computer program that combines mapping with detailed information about the physical locations of structures such as pipes, valves, and manholes within geographic areas. The system is used to help operators and maintenance personnel locate utility system features or structures and to assist with the scheduling and performance of maintenance activities.

Gasification- The conversion of soluble and suspended organic materials into gas during aerobic or anaerobic decomposition. In clarifiers the resulting gas bubbles can become attached to the settled sludge and cause large clumps of sludge to rise and float on the water surface. In anaerobic sludge digesters, this gas is collected for fuel or disposed of using a waste gas burner.

Grab Sample- A single sample of water collected at a particular time and place which represents the composition of the water only at that time and place.

Gravimetric- A means of measuring unknown concentrations of water quality indicators in a sample by weighing a precipitate or residual of the sample.

Grit- The heavy material present in wastewater, such as sand, coffee grounds, eggshells, gravel and cinders.

Grit removal- Grit removal is accomplished by accomplished by providing enlarge channel or chamber which causes the flow velocity to be reduced and allows the heavier grit to settle to the bottom of the channel where it can be removed.

Growth Rate Y- An extremely determined constant to estimate the unit growth rate of bacteria while degrading organic waste.

Head- The vertical distance, height or energy of water above a point. A head of water may be measured in either height or pressure.

Head Loss- An indirect measure of loss of energy or pressure. Flowing water will lose some of its energy when it passes through a pipe, bar screen, comminutor, filter or other obstruction. The amount of energy or pressure lost is called “head loss”. Head loss is measured as the difference in elevation between the upstream water surface and the downstream water surface and may be expressed in feet or meters.

Header- A large to which the ends of a series of smaller pipes are connected.

Headworks- The facilities where wastewater enters a wastewater treatment plant. The headworks may consist of screens, comminutors, a wet well and pumps.

Hepatitis- Hepatitis is an inflammation of the liver caused by an acute viral infection. Yellow jaundice is one symptom of hepatitis.

Hydraulic Grade Line- The surface or profile of water flowing in an open channel or a pipe flowing partially full. If a pipe is under pressure, the hydraulic grade line is at the level water would rise to in a small tube connected to the pipe. To reduce the release of odors from wastewater, the water surface or hydraulic grade line should be kept as smooth as possible

Hydraulic Jump- The sudden and usually turbulent abrupt rise in water surface in an open channel when water flowing at high velocity is suddenly retarded to a slow velocity.

Hydraulic loading- Hydraulic loading refers to the flows to a treatment plant or treatment process, Detention times, surface loading and weir overflow rates are directly influenced by flows.

Hydrogen ion concentration- The weight of hydrogen ion in moles per liter of solution. Commonly expressed as the pH value, which is the logarithm of the reciprocal of the hydrogen ion concentration.

Hydrogen Sulfide- Hydrogen sulfide is a gas with a rotten egg odor. This gas is produced under anaerobic conditions. Hydrogen sulfide gas is particularly dangerous because it dulls the sense of smell so that you don’t notice it after you have been around it for a while. In high concentrations, hydrogen sulfide gas is only noticeable for a very short time before it dulls the sense of smell. The gas is very poisonous to the respiratory system, explosive, flammable, colorless and heavier then air.

Hydrologic Cycle- The process of evaporation of water into the air and its return to earth by precipitation. This process also includes transpiration from plants, groundwater movement, and runoff into river, streams and the ocean,

Hydrolysis- 1. A chemical reaction in which a compound is converted into another compound taking up water, 2. Usually a chemical degradation of organic matter.

Hydrostatic System- In a hydrostatic sludge removal system, the surface of the water in the clarifier is higher than the surface of the water in the sludge well or hopper, this difference in pressure head forces sludge from the bottom of the clarifier to flow through pipes to the sludge well or hopper.

Hygroscopic- Absorbing or attracting moisture from the air.

Hypo chlorination- The application of hypochlorite compounds to water or wastewater for the purpose of disinfection.

Hypochlorinators- Chlorine pumps, chemical feed pumps or devices used to dispense chlorine solutions made from hypochlorites such as bleach or calcium hypochlorites into the water being treated.

Hypochlorite- Chemical compounds containing available chlorine; used for disinfection. They are available as liquids or solids in barrels, drums, and cans. Salts of hypochlorous acid.

Immediately Dangerous to Life or Health- The atmospheric concentration of any toxic, corrosive, or asphyxiate substance that poses an immediate threat to life or would cause irreversible or delayed health effects or would interfere with an individual’s ability to escape from a dangerous atmosphere.

Imoff Cone- A clear, cone shaped container marked with graduations. The cone is used to measure the volume of settleable solids in a specific volume of wastewater.

Impeller- A rotating set of vanes in a pump or compressor designed to pump or move water or air.

Impeller pump- Any pump in which the water is moved by the continuous application of power to a rotating set of vanes from some rotating mechanical source.

Incineration- The conversion of dewatered wastewater solids by combustion to ash, carbon dioxide, and water vapor.

Indicator—A substance that gives a visible change, usually of color, at a desired point in a chemical reaction, generally at a specified end point.

Indole- An organic compound containing nitrogen which has an ammonia odor.

Infiltration- The seepage of groundwater into a sewer system, including service connections. Seepage frequently occurs through defective or cracked pipes, pipe joints, connections or manhole walls.

Inflow- Water discharged into a sewer system and service connections from sources other than regular connections. This includes flow from yard drains, foundation drains and around manhole covers. Inflow differs from infiltration in that it is a direct discharge into the sewer rather than a leak in the sewer itself.

Influent- Wastewater or other liquid- raw or partially treated—flowing into a reservoir, basin, treatment process, or treatment plant.

Inhibitory Substances- Materials that kill or restrict the ability or organisms to treat waste.

Inoculate- To introduce a seed culture into a system.

Inorganic waste- Waste material such as sand, salt, iron, calcium, and other mineral materials which are only slightly affected by the action of organisms. Inorganic wastes are chemical substances usually of animal or plant origin,

Integrator- A device or meter that continuously measures and calculates a process rate variable in cumulative fashion: for example, total flows displayed in gallons, million gallons, cubic feet, or some other unit or volume measurement.

Interface- The common boundary layer between two substances such as water and a solid (metal); or between two fluids such as water and a gas; or between a liquid and another liquid.

Ionic concentration- The concentration of any ion in solution, usually expressed in moles per liter.

Ionization- The process of adding electrons to, or removing electrons from, atoms or molecules, thereby creating ions, High temperature, electrical discharges, and nuclear radiation can cause ionization.

Jar Test- A laboratory procedure that simulates coagulation/flocculation with differing chemical doses. The purpose of the procedure is to estimate the minimum coagulant dose required to achieve certain water quality goals. Samples of water to be treated are placed in six jars. Various amounts of chemicals are added to each jar, stirred and the settling of solids is observed, the lowest dose of chemicals that provides satisfactory settling is the dose used to treat the water.

Jogging- The frequent starting and stopping of an electric motor.

Joule- A measure of energy, work or quality of heat. One joule is the work done when the point of application of a force of one newton is displaced a distance of one meter in the direction of the force.

Kjeldahl- Nitrogen in the form of organic proteins or their decomposition product ammonia, as measured by the Kjeldahl Method.

Launders- Sedimentation tank effluent troughs, consisting of overflow weir plates.

Limit Switch- A device that regulates or controls the travel distance of a chain or cable.

Lineal- The length in one direction of a line. For example, a board 12 feet long has 12 lineal feet in its length.

Liquefaction- The conversion of large solid particles of sludge into very fine particles which either dissolve or remain suspended in wastewater.

Loading- Quantity of material applied to a device at one time.

Lower Explosive Limit- The lowest concentration of gas or vapor that explodes if an ignition source is present at ambient temperature. At temperature above 250 degree F the LEL decrease explosibility increases with higher temperature.

Lower Flammable Limit- The lowest concentration of a gas or vapor that burns if an ignition source is present.

Lysimeter- A device containing a mass of soil and designed to permit the measurement of water draining through the soil.

M or Molar- A molar solution consist of one gram molecular weight of a compound dissolved in enough water to make one liter of solution. A gram molecular weight is the molecular weight of a compound in grams. For example, the molecular weight of sulfuric acid is 98. A one M solution of sulfuric acid would consist of 98 grams of Hydrogen sulfide dissolved in enough distilled water to make one liter of solution.

Methylene Blue Active Substance- Another name for surfactants, or surface active agents, is methylene blue active substances, the determination of surfactants is accomplished by measuring the color change in a standard solution of methylene blue dye.

Mean Cell Residence Time- Day, an expression of the average time that a microorganism will spend in the activated sludge process.

Most probable Number- Is the most probable number of coliform-group organism per unit volume of sample water. Expressed as a density or population of organism per 100 mL of sample water.

Material Safety Data Sheet- A document which provides pertinent information and a profile of a particular hazardous substance or mixture. An MSDS is normally developed by the manufacturer or formulator of the hazardous substance or mixture. The MSDS is required to be made available to employees and operators whenever there is a likelihood of the hazardous substance or mixture being introduced into the workplace. Some manufacturers are preparing MSDSs for products that are not considered to be hazardous to show that the product or substances is NOT hazardous.

Manifold- A large pipe to which the ends of a series of smaller pipes are connected.

Manometer- An instrument for measuring pressure. Usually, a manometer is a glass tube with a liquid that is used to measure the difference in pressure across a flow measuring devise such as an orifice or a Venturi meter. The instrument used to measure blood pressure is a type of manometer.

Masking Agents- Substance used to cover up or disguise unpleasant odors. Liquid masking agents are dripped into the wastewater, sprayed into the air, or evaporated with the unpleasant fumes or odors and the discharges into the air by blowers to make an undesirable odors less noticeable.

Mechanical Aeration- The use of machinery to mix air and water so that oxygen can be absorbed into the water. Some examples are; paddle wheels, mixers, or rotating brushes to agitate the surface of an aeration tank; pumps to create fountains; and pumps to discharge water down a series of steps forming falls or cascades.

Media- The material in a trickling filter on which slime accumulates and organism grow. As settled wastewater trickles over the media, organisms in the slime remove certain types of wastes thereby partially treating the wastewater. Also the material in a rotating biological contactor or in a gravity or pressure filter.

 Median- The middle measurement or value. When several measurements are ranked by magnitude, half of the measurements will be larger and half will be smaller.

MEG- A procedure used for checking the insulation resistance on motors, feeders, bus bar systems, grounds, and branch circuit wiring.

Megger- An instrument used for checking the insulation resistance on motors, feeders, feeders, bus bar systems, ground, and branch circuit wiring.

Megohm- Meg means one million, so 5 megohms means 5 million ohms. A megger reads in millions of ohms

Meniscus- The curved surface of a column of liquid in a small tube, When the liquid wets’ the sides of the container, the curve forms a valley. When the confining sides are not wetted, the curves form a hill or upward bulge. When a meniscus forms in a measuring device, the top of the liquid level of the sample is determined by the bottom of the meniscus.

Mercaptans- Compounds containing sulfur which have an extremely offensive skunk like odor; also sometimes described as smelling like garlic or onions.

Mesophilic- Medium temperature bacteria. A group of bacteria that grow and thrive in a moderate temperature range between 68 degree and 113 degree F. The optimum temperature range for these bacteria in anaerobic digestions 85 degree F.

Metabolism- All of the processes or chemical changes in an organism or a single cell by which food is built up into living protoplasm and by which protoplasm is broken down into simpler compounds with the exchange of energy.

Micron- Micrometer of micron. A unit of length. One millionth of a meter or one thousandth of a millimeter. One micron equals 0.00004 of an inch.

Microorganisms- Very small organisms that can be seen only through a microscope. Some microorganisms use the wastes in wastewater for food and thus remove or alter much of the undesirable matter.

Microscreen- A device with a fabric staining media with opening usually between 20 and 60 microns. The fabric is wrapped around the outside of a rotating drum. Wastewater enters the open end of the drum and throws it through the rotating screen cloth. At the highest point of the drum, the collected solids are backwashed by high-pressure water jets into a trough located within the drum.

Milligrams per liter- A measure of the concentration by weight of a substance per unit volume. For practical purposes, one mg/L of a substance in ware is equal to one part per million parts. Thus a liter of water with a specific gravity of 1.0 weighs one million milligrams. If it contains 10 milligrams of dissolved oxygen, the concentration is 10 million milligrams, or 10 milligrams per liter, or 10 parts of oxygen per million parts of water, or 10 parts per million.

Millimicron- A unit of length equal to 10-3 u (one thousandth of a micron).

Mixed Liquor- When the activated sludge in an aeration tank is mixed with primary effluent or the raw wastewater and return sludge, this mixture is then referred to as mixed liquor as long as it is in the aeration tank. Mixed liquor also may refer to the contents of mixed aerobic or anaerobic digesters.

Mixed Liquor suspended solids- Suspended solids in the mixed liquor of an aeration tank.

Mixed Liquor Volatile Suspended Solids- The organic or volatile suspended solids in the mixed liquor of an aeration tank. This volatile portion is used as a measure or indication of the microorganisms present.

Molecular Oxygen- The oxygen molecular, O2, which is not combined with another element to forma compound.

Molecular weight- The molecular weight of a compound in grams is the sum of the atomic weights of the elements in the compounds, the molecular weight of sulfuric acid in grams is 98.

Molecule- The smallest division of a compound that still retains or exhibits all the properties if the substances.

Motile- Capable of self-propelled movement. A term that is sometimes used to distinguish between certain types of organisms found in water.

Moving average- To calculate the moving average for the last 7 days, add up the values for the last 7 days and divide by 7. Each day add the most recent day’s value to the sum of values and subtract the oldest value. By using the 7 day moving average, each day of the week is always represented in the calculations.

Muffle Furnace- A small oven capable of reaching temperatures up to 600 degree Celsius. Muffle furnaces are used in laboratories for burning or incinerating samples to determine the amounts of

Multi Stage Pump- A pump that has more than one impeller, a single stage pump has one impeller.

Normal- A normal solution contains one gram equivalent weight of reactant per liter of solution. The equivalent weight if an acid is that weight which contains one gram atom of ionizable hydrogen or its chemical equivalent.

National Institute of Occupational Safety and Health- Is an organization that tests and approves safety equipment for particular applications. NIOSH is the primary federal agency engaged in research in the national effort to eliminate on the job hazards to the health and safety of the working people. The NIOSH Publications Catalog, Seventh edition, NIOSH Pub. No 87-115, lists the NIOSH publications concerning industrial hygiene and occupational health. To obtain a copy of the catalog, write to National Technical information Service, 5285 Port Royal Road, Springfield, VA 22161.

National Pollutant Discharge Elimination system permit is the regulatory agency document issued by either a federal or state agency which is designed to control all discharges or potential pollutants from point sources and storm water runoff into US waterways. NPDES permits regulate discharges into navigable water from all point sources of pollution, including industries, municipal wastewater treatment plants, sanitary landfills. Large agricultural feedlots and return irrigation flows.

Nameplate- A durable metal plate found on equipment which lists critical operating conditions for the equipment.

Neutralization- Addition of an acid or alkali to a liquid to cause pH of the liquid to move toward a neutral pH of 7.0

Nitrification- An aerobic process in which bacteria change the ammonia and organic nitrogen in wastewater into oxidized nitrogen. The second stage BOD is sometimes referred to as the “nitrogenous BOD”

Nitrification Stage- A stage of decomposition that occurs in biological treatment processes when aerobic bacteria, using dissolved oxygen, change nitrogen compounds into oxidized nitrogen. The second stage BOD is sometimes referred to as the “nitrification stage”.

Nitrifying Bacteria- Bacteria that change the ammonia and organic nitrogen in wastewater into oxidized nitrogen.

Nitrogenous- A term to describe chemical compounds containing nitrogen in combined forms. Proteins and nitrate are nitrogenous compounds.

Nomogram- A chart or diagram containing three or more scales used to solve problems with three or more variable instead of using mathematical formulas.

Noncorrodible- A material that resist corrosion and will not be eaten away by wastewater or chemicals in wastewater.

Nonsparking Tools- These tools will not produce a spark during use. They are made of a nonferrous material, usually a copper-beryllium alloy.

Nonvolatile Matter- Material such as sand, salt, iron, calcium, and other materials which are only slightly affected by the actions of organisms and are not lost on ignition of the dry solids at 550 degree Celsius. Volatile materials are chemical substances usually of aniamal or plant origin.

Notice- This word calls attention to information that is especially significant in understanding and operating equipment or processes safely.

Nutrient cycle- The transformation or change of a nutrient from one form to another until the nutrient has return to the original form, thus completing the cycle, The cycle may take place under either aerobic or anaerobic conditions.

Nutrients- Substances which are required to support living plants and organisms, Major nutrients are carbon, hydrogen oxygen, sulfur, nitrogen, and phosphorus. Nitrogen and phosphorus are difficult to remove from wastewater by conventional treatment processes because they are water soluble and tend to recycle.

Operation and Maintenance Manual- A manual that describes detailed procedures for operators to follow to operate and maintain a specific wastewater treatment or pretreatment plant and the equipment of that plant.

OSHA- the Williams-Steiger Occupational Safety and Health Act of 1970 is a federal law designed to protect the health and safety of industrial workers and treatment plant operators. It regulates the design, construction, operation and maintenance of industrial plants and wastewater treatment plants. The Act does not apply directly to municipalities, EXCEPT in those states that have approved plans and have asserted jurisdiction under section 18 of the OSHA Act.

Obligate Aerobes- Bacteria that must have atmospheric or dissolved molecular oxygen to live and reproduce.

Odor Panel- A group of people used to measure odors.

Offset- The difference between the actual value and the desired values; characteristic of proportional controllers that do not incorporate reset action.

Olfactometer- A device to measure odors in the field by diluting odors with odor free air.

Olfactory- A condition in which a person’s nose, after exposure to certain odors, is no longer able to detect odor.

Operating Ratio- The operating ratio is a measure of the total revenues divided by the total operating expensive.

Organic waste- Waste material which comes mainly from animal or plant sources, Organic wastes generally can be consumed by bacteria and other small organisms. Inorganic wastes are chemical substances of mineral origin.

Organism- Any form of animal or plant life.

Organizing-Deciding who does what work and delegating authority to the appropriate persons.

Orifice- An opening in a plate, wall, or partition. In a trickling filter distributor, the wastewater passes through an orifice to the surface of the filter media. An orifice flange or plate placed in a pipe consists of a slot or a calibrated circular hole smaller the pipe diameter. The difference in pressure in the pipe above and at the orifice may be used to determine the flow in the pipe.

Orthotodine- Orthotolidine is a colorimeteris indicator of chlorine residual. If chlorine is present, a yellow colored compound is produced. This reagent is no longer approved for tests of effluent chlorine residual.

Ouch Principle- This principle says that as a manager when you delegate job tasks you must be objective, Uniform in your treatment of employees, Consistent with utility policies and have job relatedness.

Outfall- 1. The point, location or structure where structure where wastewater or drainage discharge from a sewer, drain, or other conduit, 2. The conduit leading to the final disposal point or area.

Overflow Rate- One of the guidelines for the design of settling tanks and clarifiers in treatment plants. Used by operators to determine if tanks and clarifiers are hydraulically over-or overloaded.

Overturn- The almost spontaneous mixing of all layers of water in a reservoir or lakes when the water temperature become similar from top to bottom. This may occur in the fall/winter when the surface waters cool to the same temperature as the bottom waters and also in the spring when the surface waters warm after the ice melts. This is also called “turnover”.

Oxidation- Oxidation is the addition of oxygen, removal of hydrogen, or the removal of electrons from an element or compound. In wastewater treatment, organic matter is oxidized to more stable substances.

Oxidation State/Oxidation Number- In a chemical formula, a number accomplished by a polarity indication that together indicates the change of an ion as well as the extent to which the ion has been oxidized or reduced in a Redox Reaction.

Oxidation Reduction Potential- The electrical potential required to transfer electrons from one compound or element to another compound or element; used as a qualitative measure of the state of oxidation in wastewater treatment systems. ORP is measured in millivolts, with negative values indicating a tendency to reduce compounds or elements and positive values indicating a tendency to oxidize compounds or elements.

Oxidation Reduction Reaction- A two part reaction between two substances involving a transfer or electrons from one substance to the other. Oxidation is the loss of electrons by one substance, and reduction is the acceptance of electrons by the other substance. Reduction refers to the lowering of the Oxidation State or Oxidation Number of the substance accepting the electrons. In redox reaction, the substance that gives up the electrons is called the reductant because it causes a reduction on the oxidation state or number of the substance that accepts the transferred electrons. The substance that receives the electrons is called the oxidant because it causes oxidation of the other substance. Oxidation and reduction always occur simultaneously.

Oxidized Organics- Organic material that have been broken down in a biological process, Examples of these materials are carbohydrates and proteins that are broken down to simple sugars.

Oxidizing Agent- Any substance, such as oxygen or chlorine that will readily add electrons. When oxygen or chlorine is added to wastewater, organic substances are oxidized. These oxidized organic substances are more stable and less likely to give off odors that contain disease-causing bacteria. Oxygen

Deficiency- An atmosphere containing oxygen at a concentration of less than 19.5 percent by volume.

Oxygen Enrichment- An atmosphere containing oxygen at a concentration of more that 23.5 percent by volume.

Ozonztion- The application of ozone to water, wastewater, or air, generally for the purpose of disinfection or odor control.

Publically Owned Treatment Works- A treatment works which is owned by a state, municipality, city, town, special sewer district of other publicly owned and financed entity as opposed to a privately owned treatment facility. This definition included any devices and systems used in the storage, treatment, recycling and reclamation of municipal sewage or industrial waste of a liquid nature. It also included sewers, pipes and other conveyances only if they carry wastewater to a POTW treatment plant. The term also means the municipality which has jurisdiction over the indirect discharge to and the discharges from such a treatment works.

Package treatment Plant- A small wastewater treatment plant often fabricated at the manufacturer’s factory, hauled to the site, and installed as one facility. The package may be either a small primary or a secondary wastewater treatment plant.

Parallel Operation- Wastewater being treated is split and a portion flows to one treatment unit while the remainder flows to another similar treatment.

Parasitic Bacteria- Parasitic bacteria are those bacteria which normally live off another living organism, known as the “host”

Pathogenic- Bacteria, viruses, cysts, or protozoa which can cause disease in a host. There are many types or organism which do NOT cause disease and which are not called pathogenic. Many beneficial bacteria are found in wastewater treatment process actively cleaning up organic wastes.

Percent Saturation- The amount of a substance that is dissolved in a solution compared with the amount dissolved in the solution at saturation, expressed as a percent.

Percolation- The movement or flow of water through soil or rocks.

Peristaltic Pump- A type of positive displacement pump.

Ph- pH is an expression of the intensity of the basic or acidic condition of a liquid. Mathematically, pH is the logarithm of the reciprocal of the hydrogen ion activity.

Phenol- An organic compound that is a derivative of benzene.

Phenolphthalein Alkalinity- A measure of the hyrdroxide ions plus one half of the normal carbonate ions in aqueous suspension. Measured by the amount of sulfuric acid required to lower the water to a pH value of 8.3, as indicated by a change in color of phenolphthalein. It is expressed as milligrams per liter of equivalent calcium carbonate.

Photosynthesis- A process in which organisms, with the aid of chlorophyll, convert carbon dioxide and inorganic substances into oxygen and additional plant material, using sunlight of energy. All green plants grow by this process.

Physical Waste Treatment Process- Physical waste treatment processes include racks, screens, comminutors, clarifiers and filtration. Chemical or biological reactions are important treatment processes, but NOT part of a physical treatment process.

Pillows- Plastic tubes shaped like pillows that contain exact amount of chemicals or reagents. Cut open the pillow, pour the reagents into the sample being testes, mixed thoroughly and follow test procedures

Planning- Management of utilities to build the resources and financial capability to provide for future needs.

Plug Flow- A type of flow that occurs in tanks, basins or reactors when a slug of wastewater moves through a tank without ever dispersing or mixing with the rest of the wastewater flowing through the tank. 

Pole Shader- A copper bar circling the laminated iron core inside the coil of a magnetic starter.

Pollution- The impairment of water quality by agricultural, domestic or industrial wastes to a degree that the natural water quality is changed to hinder and beneficial use of the water or render it offensive to the senses of sight, taste, or smell or when sufficient amounts of wastes create or pose a potential threat to human health or the environment.

Polyelectrolyte- A high molecular weight substance that is formed by either a natural or synthetic process. Natural polyelectrolytes may be of biological origin or derived from starch products, cellulose derivatives, and alignates. Synthetic polyelectrolytes of simple substance that have been made into complex, high molecular weight substances

Polymer- A long chain molecular formed by the union of many monomers. Polymers are used with other chemical coagulants to aid in binding small suspended particles to larger chemical flocs for their removal from water.

Polysaccharide- A carbohydrate, such as starch, insulin or cellulose, composed of chains of simple sugars.

Ponding- A condition occurring on trickling filters when the hollow spaces become plugged to the extent that water passage through the filter is inadequate. Ponding may be the result of excessive slime growths, trash, or media breakdown.

Population Equivalent- A means of expressing the strength of organic material in wastewater. In a domestic wastewater system, microorganisms use up about 0.2 pound of oxygen per day for each person using the system. May also be expressed as flow or suspended solids.

Positive pressure- A positive pressure is a pressure greater than atmospheric. It is measured as pounds per square inch or as inches of water column. A negative pressure is less than atmospheric and is sometimes measured in inches or mercury. In the metric system pressure are measured in kg/sq cm or pascal.

Postchlorination- The addition of chlorine to the plant discharge or effluent, FOLLOWING plant treatment, for disinfection purposes.

Potable Water- Water that does not contain objectionable pollution, contamination, minerals or infective agents and is considered satisfactory for drinking.

Pre-Aeration- The addition of air at the initial stages of treatment to freshen the wastewater, remove gases, add oxygen, promote flotation of grease, and aid coagulation.

Prechlorination- The addition of chlorine in the collection system serving the plant or at the headworks of the plant PRIOR TO other treatment processes mainly for odor and corrosion control. Also applied to aid disinfection, to reduce plant BOD load, to aid in settling, to control foaming in Imhoff units and to help remove oil.

Prechlorination-1. An insoluble, finely divided substance which is a product of a chemical reaction with a liquid, 2. The separation from solution of an insoluble substance.

Precoat- Application of a free-draining, noncohesive material such as diatomaceous earth to a filtering media. Precoating reduces the frequency of media washing and facilitates cake discharge.

Preliminary Treatment- The removal of metal, rocks, rags, sand, eggshells, and similar material which may hinder the operation of a treatment plant. Preliminary treatment is accomplished by using equipment such racks, bar screens, comminutors, and grit removal systems.

Present Worth- The value of a long-term project expressed in today dollars. Present worth is calculated by converting all future benefits and costs over the life of the project to a single economic values at the start of a project. Calculating the present worth of alternative project makes it possible to compare them and select the one with the largest positive present worth or minimum present cost.

Pretreatment Facility- Industrial wastewater treatment plant consisting of one or more treatment devices designed to remove sufficient pollutants from wastewaters to allow an industry to comply with effluent limits established by the US EPA General and Categorical Pretreatment Regulations or locally derived prohibited discharge requirement and local effluents limits. Compliance with effluent limits allows for a legal discharge to a POTW.

Primary Treatment- A wastewater treatment process that takes place in a rectangular or circular tank and allows those substances in wastewater that readily settles or float to be separated from the water being treated.

Process Variable- A physical or chemical quantity which is usually measured and controlled in the operation of a wastewater treatment plant or an industrial plant.

Programmable Logic Controller- A small computer that controls process equipment and can control the sequence of valve operation.

Proteinaceous- Materials containing proteins which are organic compounds containing nitrogen.

Protozoa- A group of motile microscopic organisms that sometimes cluster into colonies and generally consume bacteria as an energy source.

Prussian Blue- A blue paste or liquid used to show a contact area. Used to determine of gate valve seats fits properly.

Psychrophilic- Cold temperature bacteria. A group of bacteria that grow and thrive in temperatures below 68 degrees f.

Purge- To remove a gas or vapor from a vessel, reactor or confined space, usually by displacement or dilution.

Putrefaction- Biological decomposition of organic matter with the production of foul-smelling products associated with anaerobic conditions.

Putrescible- Material that will decompose under anaerobic conditions and produce nuisance odors.

Pyrometer- An apparatus used to measure high temperatures.

Rack- Evenly spaced parallel metal bars or rods located in the influent channel to remove rags, rocks, and can from the wastewater.

Radial to Impeller- Perpendicular to the impeller shaft. Material being pumped flows at a right angle to the impeller.

Raw Wastewater- Plant influent or wastewater BEFORE any treatment.

Reagent- A pure chemical substance that is used to make new products or is used in chemical tests to measure, detect, or examine other substances.

Recalcination- A lime recovery process in which the calcium carbonate in sludge is converted to lime by heating at 1,800 degree F.

Recarbonation- A process in which carbon is bubbled into the water being treated to lower pH.

Receiving Water- A stream, river, lake, ocean, or other surface or groundwaters into which treated or untreated wastewater is discharged.

Recharge Rate- Rate at which water is added beneath the ground surface to replenish or recharge groundwater.

Recirculation- The return of part of the effluent from a treatment process to the incoming flow.

Redox- Oxidation reduction reactions in which the oxidation state if at least one reactant is raised while that of another is lowered.

Reducing Agent- Any substance, such as base metal or the sulfide ion, that will readily donate electrons. The opposite is an Oxidizing Agent.

Reductin- Reduction is the addition of hydrogen, removal of oxygen, or the addition of electrons to an element or compound. Under anaerobic conditions, sulfur compounds are reduced to odor-producing hydrogen sulfide and other compounds. The opposite is Oxidation.

Reflux- Flow back. A sample is heated, evaporates, cold, condenses, and flows back to the flask.

Refractory Materials- Materials difficult to remove entirely from wastewater such as nutrients, color, taste- and odor- producing substances and some toxic material.

Reliqefaction- The return of a gas to the liquid state; for example. A condensation of chlorine gas to return it to its liquid form by cooling

Representative Sample- A sample portion of material or wastestream that is as nearly identical in content and consistency as possible to that in the larger body of material or wastestream being sample.

Residual Chlorine- The concentration of chlorine present in water after the chlorine demand has been satisfied. The concentration is expresses in terms of the total chlorine residual, which includes both the free and combined or chemically bound chlorine residuals.

Respiration- The process in which an organism uses oxygen for its life processes and gives off carbon dioxide.

Responsibility- Answering to those above in the chain of command to explain how and why you have used you authority.

Retention Time- The time water, sludge or solids are retained or held in a clarifier or sedimentation tank.

Riprap- Broken stones, boulders, or other materials placed compactly or irregularly on levees or dikes for the protections of earth surfaces against the erosive action of waves.

Rising Sludge- Rising sludge occurs in the secondary clarifiers if activated sludge plants when the sludge settles to the bottom of the clarifier, is compacted, and then stated to rise to the surface, usually as a result of denitrification, or anaerobic biological activity that produces carbon dioxide and/or methane.

Rotometer- A device used to measure the flow rate of gases and liquids, the gas or liquid being measured flows vertically up a tapered, calibrated tube. Inside the tube is a small ball or bullet shaped float that raises or falls depending on the flow rates. The flow rate may be read on a scale behind or on the tube by looking at the middle of the ball or at the widest part or top of the float.

Rotary Pump- A type of displacement pump consisting essentially of elements rotating in a pump case which they closely fit. The rotation of these elements alternately draws in and discharges the water being pumped. Such pumps act with neither suction nor discharge valves, operate at almost any speed and do not depend on centrifugal forces to lift the water.

Rotating Biological Contactors- A secondary biological treatment process for domestic and biodegradable industrial wastes. Biological contactors have rotating “shaft” surrounded by plastic discs called the “media”. The shaft and media are called the “drum”. A biological slime grows on the media when conditions are suitable and the microorganisms that make up the slime stabilize the waste products by using the organic material for growth and reproduction.

Rotifers- Microscopic animals characterized by short hairs on their front end.

Sodium Absorption Ratio- This ratio expresses the relative activity of sodium ions in the exchange reactions with soil.

Supervisory Control And Data Acquisition system- A computer-monitored alarm, response, control and data acquisition system used by operators to monitor and adjust their wastewater treatment processes and facilities.

SCFM- Cubic Feet of air per minute at standard conditions of temperature, pressure, and humidity.

Sludge Volume Index- This is a calculation which indicates the tendenancy of activated sludge solids to thicken or to become concentrated during the sedimentation/thickening process. SVI is calculated in the following manner: allow a mixed liquor sample from the aeration basin to settle for 30 minutes; (2) determine the suspended solids concentration for a sample of the same mixed liquor; (3) calculate SVI by dividing the measured wet volume of the settles sludge by the dry weight concentration of MLSS in grams/L

Sacrificial Anode- An easily corroded material deliberately installed in a pipe or tank. The intent of such an installation is to give up this anode to corrosion while the water supply facilities remain relatively corrosion free.

Sanitary Sewer- A pipe or conduit intended to carry wastewater or waterborne wastes from homes, businesses, and industries to the POTW. Storm water or unpolluted water should be collected and transported in a separate system of pipes or conduits to natural watercourses.

Saprophytic Organisms- Organisms living on dead or decaying organic matter. They help natural decomposition of the organic solids in wastewater.

Screen- A device used to retain or remove suspended or floating objects in wastewater. The screen has openings that are generally uniform in size. It retains or removes objects larger than the openings. A screen may consist of bars, rods, wires, gratings, wire mesh, or perforated plates.

Sealing Water- Water used to prevent wastewater or dirt from reaching moving parts. Sealing water is at higher pressure than the wastewater it is keeping out of a mechanical device.

Secchi Disc- A flat, white disc lowered into the water by a rope until it is just barely visible. At this point, the depth of the disc from the water surface is the recorded Secchi disc transparency.

Secondary Treatment- A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually the process follows primary treatment by sedimentation. The process commonly is a type of biological treatment process followed by secondary clarifiers that allow the solids to settle out from the water being treated.

Seed Sludge- In wastewater treatment. Seed, seed culture or seed sludge refers to a mass of sludge which contains populations of microorganisms. When a seed sludge is mixed with wastewater or sludge being treated, the process of biological decomposition takes places more rapidly.

Seizing- Seizing occurs when an engine overheats and a component expands to the point where the engine will not run. Also called freezing.

Septic- A condition produced by anaerobic bacteria. If severe, the sludge produces hydrogen sulfide, turns black, gives off foul odors, contains little or no dissolved oxygen, and the wastewater has a higher oxygen demand.

Septicity- Septicity is the condition in which organic matter decomposes to form foul smelling products associated with the absence of the free oxygen. If severe, the wastewater produces hydrogen sulfide, turns black, gives off foul odors, contains little or no dissolved oxygen, and the wastewater has high oxygen demand.

Series Operation- Wastewater being treated flows through one treatment unit and then flows through another similar treatment unit.

Set Point- The position at which the control or controller is set. This is the same as the desired value of the process variable.

Sewage- The used household water and water-carried solids that flow in sewers to a wastewater treatment plant.

Sewer Gas- 1) Gas in collection lines that result from the decomposition of organic matter in the wastewater. When testing for gases found in sewers, test for lack of oxygen and also for explosive and toxic gases. 2) Any gas present in the wastewater collection system, even though it is such sources as gas mains, gasoline, and cleaning fluid.

Shear Pin- A straight pin that will fail when a certain load or stress is exceeded. The purpose of the pin is to protect equipment from damage due to the excessive loads or stresses.

Shock Load- The arrival at a plant of a waste which is toxic to organisms in sufficient quality or strength to cause operating problems. Possible problems include odors and bulking sludge which will result in a high loss of solids from the secondary clarifiers into the plant effluent and a biological process upset that may require several days to a week to recover. Organic or hydraulic overloads also can cause shock load.

Short Circuiting- A condition that accurse in tanks or basins when some of the flowing water entering a tanks or basin flows along a nearly direct pathway from the inlet to the outlet. This is usually undesirable since it may result in shorter contact, reaction, or settling times in comparison with the theoretical or presumed detention times.

Shredding- Comminution. A mechanical treatment process which cuts large pieces of waste into smaller pieces so they won’t plug pipes or damage equipment.

Sidestream- Wastewater flows that develop from other storage or treatment facilities. This wastewater may or may not need additional treatment.

Significant Figure- The number of accurate numbers in a measurement. If the distance between two points is measured to the nearest hundredth and recorded as 238.42 feet, the measurement has five significant figures.

Single Stage Pump- A pump that has only one impeller. A multi-stage pump has more than one impeller.

Skatole- An organic compound that contains nitrogen and has a fecal odor.

Slake- To mix with water so that a true chemical combination takes place, such as in the slaking of lime.

Sloughings- Tricking filter slimes that have been washed off the filter media, they are generally quite high in BOD and will lower effluent quality unless removed.

Sludge- 1) The settable solids separated from the liquids during processing, 2) The deposits of foreign materials on the bottoms of streams or other bodies of water.

Sludge Age- A measure of the length of time a particle of suspended solids has been retained in the activated sludge process.

Sludge Density Index- This calculation is used in a way similar to the sludge Volume Index to indicate the settle ability of sludge in a secondary clarifier or effluent. The weigh in grams of one milliliter of sludge after settling for 30 minutes

Sludge Digestion- The process of changing organic matter are converted into gas or a more stable solid form. These changes take place as microorganisms feed on sludge in anaerobic or aerobic digesters

Sludge Gasification- A process in which soluble and suspended organic matter are converted into gas by anaerobic decomposition. The resulting gas bubbles can become attached to the settled sludge and cause large clumps of sludge to rise and float on the water surface.

Sludge Volume Index- This is a calculation which indicates the tendency of activated sludge solids to thicken it to become concentrated during the sedimentation/thickening process. SVI is calculated in the following manner: 1. Allow a mixed liquor sample from the aeration basin to settle for 30 minutes; 2. Determine the suspended solids concentration for a sample of the same mixed liquor; 3. Calculate SVI by dividing the measured wet volume of the settled sludge by the dry weight concentration of MLSS in grams/L.

Sludge Volume Ratio- The volume of sludge blanket divided by the daily volume of sludge pumped from the thickener.

Slugs- Intermittent releases or discharges of industrial waste.

Slurry- A thin, watery mud or any substance resembling it.

Sodium Adsorption Ratio- This ration expresses the relative activity of sodium ions in the exchange reactions with soil

Software Programs- Computer programs; list of instructions that tell a computer how to perform a given task or tasks, some software programs are designed and written to monitor and control municipal wastewater treatment processes.

Solids Concentration- The solids in the aeration tank which carry microorganisms that feed on wastewater. Expressed as milligrams per liter of mixed liquor Volatile Solids.

Soluble BOD- Soluble BOD is the BOD of water that has been filtered in the standard suspended solids test. The soluble BOD is a measure of food for microorganisms that is dissolved in the water being treated.

Solute- The substance dissolved in a solution. A solution is made up of the solvent and the solute.

Solution- A liquid mixture of dissolved substances. In a solution it is impossible to see all the separate parts.

Specific Gravity-1) Weight of a particle, substance or chemical solution in relation to the weight of an equal volume of water. Water has a specific gravity of 1.000 at 4 degree Celsius. Wastewater particles or substances usually have a specific gravity of 0.5 to 2.5, 2) Weight of a particular gas in relation to the weight of an equal volume of air at the same temperature and pressure. Chlorine has a specific gravity of 2.5 as a gas.

Splash Pad- A structure made of concrete or other durable material to protect bare soil from erosion by splashing or falling water.

Soil- Excavated material such as soil from the trench of a sewer.

Stabilize- To convert to a form that resists change. Organic material is stabilized by bacteria which convert the material to gases and other relatively inert substances. Stabilized organic material generally will not give obnoxious odors.

Stabilize- To convert to a form that resists change. Organic materials is stabilized by bacteria which convert the material to gases and other relatively inert substances. Stabilized organic material generally will not give off obnoxious odors.

Stabilized Waste- A waste that has been treated or decomposed to the extent that, if discharged or released, its rate and state of decomposition would be such that the waste would not cause a nuisance or odors in the receiving water

Standard Solution- A solution in which the exact concentration of a chemical or compound is known.

Standard Solution- A solution in which the exact concentration of a chemical or compound is known.

Standardize- To compare with a standard. 1) In wet chemistry, to find out the exact strength of a solution by comparing it with a standard of known strength. This information is used to adjust the strength by adding more water or more of the substance dissolved. 2) To set up an instrument or device to read a standard. This allows you to adjust the instrument so that it reads accurately, or enables you to apply a correction factor to the readings.

Stasis- Stagnation or inactivity of the life processes within organisms.

Static head- When water is not moving, the vertical distance from a specific point to the water surface is the static head.

Stator- That portion of a machine which contains the stationary parts that surround the moving parts.

Step Feed Aeration- Step feed aeration is a modification of the conventional activated sludge process, in step aeration, primary effluent enters the aeration tank at several points along the length of the tank, rather than all of the primary effluent entering at the beginning or head of the tank and flowing through the entire tank in a plug flow mode.

Sterilization- The removal or destruction of all microorganisms, including pathogenic and other bacteria, vegetative forms and spores.

Stethoscope- An instrument used to magnify sounds and convey them to the ear.

Stop Log- A log or board in an outlet box or device used to control the water level in ponds and also the flow from one pond to another pond or system.

Storm Sewer- A separate pipe, conduit or open channel that carries runoff from storms, surface drainage, and street wash, but does not include domestic and industrial wastes. Storms sewers are often the recipients of hazardous or toxic substances due to the illegal dumping of hazardous waste or spills creates by accidents involving vehicles and trains transporting these substances,

Stripped Gases- Gases that are released from a liquid by bubbling air through the liquid to be sprayed or tumbled over media.

Stripped Odors- Odors that are released from a liquid by bubbling air through the liquid or by allowing the liquid to be sprayed or tumbled over media.

Struvite- A deposit or precipitate of magnesium ammonium phosphate hexahydrate found on the rotating compounds of centrifuges and centrate discharge lines. Struvite can be formed when anaerobic sludge comes in contact with spinning centrifuge components rich in oxygen in the presence of microbial activity. Struvite can also be formed in digested sludge lines and valves in the presence of oxygen and microbial activity. Struvite can form when the pH levels is between 5 and 9.

Stuck- Not working. A stuck digester does not decompose organic matter properly. The digester is characterized by low gas production, high volatile acid and alkalinity relationship, and poor liquid-solids separation. A digester in a stuck condition is sometimes called a “sour” or “upset” digester.

Substrate- 1. The base on which an organism lives. The soil is the substrate of most seed plants; rocks, soil, water, or other plants or animals are substances for other organisms. 2. Chemical used by an organism to support growth. The organic matter in wastewater is a substrate for the organisms in activated sludge.

Suction Head- The positive pressure [in feet (meters) or pounds per square inch] on the suction side of a pump. The pressure can be measures from the centerline of the pump UP TO the elevation of the hydraulic grade line on the suction side of the pump.

Suction Lift- the NEGATIVE pressure [in feet (meters) or inches (centimeters) of mercury vacuum] on the suction side of the pump. The pressure can be measured from the centerline of the pump DOWN TO (LIFT) the elevation of the hydraulic grade line on the suction side of the pump.

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

Surface-Active Agent- The active agent in detergents that possesses a high cleaning ability. Also called SURFACTANTS.

Surface Loading- One of the guidelines for the design of settling tanks and clarifiers in treatment plants. Used by operators to determine of tanks and clarifiers are hydraulically over-or underloaded.

Surfactant- Abbreviation for surface-active agent. The active agent in detergent that possesses a high cleaning ability.

Suspended Solids- 1. Solids that either float on the surface or are suspended in water, wastewater, or other liquids and which are largely removable by laboratory filtering. 2. The quantity of material removed from wastewater in a laboratory test, as prescribed in STANDARD METHIDS FOR THE EXAMINATION OF WATER AND WASTEWATER, and referred to as Total Suspended Solids Dried at 103-105 degree Celsius.

Total Organic Carbon- TOC measures the amount of organic carbon in water.

Tailgate Safety Meeting- Brief safety meeting held every 7 to 10 working days. The term tailgate comes from the safety meeting regularly held by the construction industry around the tailgate of a truck.

Tertiary- Any process of water renovation that upgrades treated wastewater to meet specific reuse requirements. May included general cleanup of water or removal of specific parts of waste insufficiently removed by conventional treatment processes. Typical processes include chemical treatment and pressure filtration.

Thermophilic- Hot temperature bacteria. A group of bacteria that grows and thrive in temperatures above 113 degree F. The optimum temperature range for these bacteria in anaerobic decomposition is 120 degree F to 135 degree F. Aerobic thermophilic bacteria thrive between 120-158 degree F.

Thief Hole- A digester sampling well which allows sampling of the digester contents without venting digester gas.

Threshold Odor- The minimum odor of a sample that can just be detected after successive odorless dilutions.

Thrust Block- A mass of concrete or similar material appropriately placed around a pipe to prevent movement when the pipe is carrying water. Usually placed at bends and valves structures.

Time Lag- The time required for processes and control systems to respond to a signal or to reach a desired level.

Time Weighted Average- The average concentration of a pollutant based on the times and levels of concentrations of the pollutants. The time weighted average is equal to the sum of the portions of each time period multiplied by the pollutant concentration during the time period divided by the hours in the workday. 8TWA PEL is the Time Weighted Average permissible exposure limit, in parts per million, for a normal 8-hour work day and a 40-hour workweek to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.

Titrate- To titrate a sample, a chemical solution of known strength is added drop by drop until a certain color change, precipitate, or pH change in the sample is observed. Titration is the process of adding the chemical reagent in small increments until completion of the reaction, as signaled by the end point.

Total Chlorine- The total concentration of chlorine in water, including the combined chlorine and the free available chlorine.

Total Chlorine Residual- The total amount of chlorine residual present in a water sample after a given contact time.

Total Dynamic Head- When a pump is lifting or pumping water, the vertical distance from the elevation of the energy grade line on the suction side of the pump to the elevation of the energy grade line on the discharge side of the pump.

Totalizer- A device or meter that continuously measures and calculates a process rate variable in cumulative fashion; for example, total flows displayed in gallons, million gallons, cubic feet, or some other unit of volume measurement

Toxic- A substance which is poisonous to a living organism.

Toxicity- The relative degree of being poisonous or toxic. A condition which may exist in wastes and will inhibit or destroy the growth or function of certain organisms.

Transpiration- The process by which water vapor is released to the atmosphere by living plants. This process is similar to people sweating

Tricking Filter- A treatment process in which the wastewater trickles over the media that provide the opportunity for the formation of slimes and biomass which contain organisms that feed upon and remove waste from the water being treated.

Trickling Filter Media- Rocks or other durable materials that make up the body of the filter. Synthetic media have been used successfully.

Trunk Sewer- A sewer that receives wastewater from many tributary branched or sewers and serves a large territory and contributing population.

Turbid- Having a cloudy or muddy appearance.

Turbidity Meter- An instrument for measuring and comparing the turbidity of liquids by passing light through them and determine how much light is reflected by the particles in the liquid. The normal measuring range is 0 to 100 and is expressed as Nephelometric Turbidity Units

Turbidity Units- Turbidity units are a measure of the cloudiness of water. If measured by a nephelometric instrumental procedure, turbidity units are expressed in nephelometric turbidity units or simply TU. Those turbidity units obtained by visual methods are expressed in Jackson Turbidity Units which are a measure of the cloudiness of water; they are used to indicate the clarity of water. There is no real connection between NTUs and JTUs. The Jackson turbidity meter is a visual method and the nephelometer is an instrumental method based on deflected light.

Two- Stage Filters- Two filters are used. Effluent from the first filter goes to the second filter, either directly or after passing through a clarifier.

Ultrafiltration- A membrane filter process used for the removal of some organic compounds in an aqueous solution.

Upper Explosive Limit- The point at which the concentration of a gas in air becomes too great to allow an explosion upon ignition due to insufficient oxygen present.

Upset- An upset digester does not decompose organic properly. The digester is characterized by low gas production, high volatile acid/alkalinity relationship, and poor liquid-solids separation. A digester in an upset condition is sometimes called a “sour” or “stuck” digester.

Velocity Head- The energy in flowing water as determined by a vertical height equal to the velocity of flowing water divided by twice the acceleration due to gravity.

Viscosity- A properly of water, or any other fluid, which resist efforts to change its shape or flow. Syrup is more viscous than water. The viscosity of water increase significantly as temperatures decrease. Motor oil is related by how thick it is; 20 weight oil is considered relatively thin while 50 weight oil is relatively thick or viscous.

Volatile- 1. A volatile substance is one that is capable of being evaporated or changed to a vapor at relatively low temperatures. Volatile substances also can be partially removed by air stripping. 2. In terms of solids analysis, volatile refers to materials lost upon ignition in a muffle furnace for 60 minutes at 550 degree Celsius. Natural volatile materials are chemical substances usually of animal or plant origin. Manufactured or synthetic  volatile materials such as either and carbon tetrachloride are highly volatile and not of plant or animal origin.

Volatile Acids- Fatty acids produced during digestion which are soluble in water and can be steamed-distilled at atmospheric pressure. Also called organic acids. Volatile acids are commonly reported as equivalent to acetic acid.

Volatile Liquids- Liquids which easily vaporize or evaporate at room temperature.

Volatile Matter- Matter in water, wastewater, or other liquids that are lost on ignition of the dry solids at 550 degree Celsius.

Volatile Solids- Those solids in water, wastewater, or other liquids that are lost on ignition of the dry solids at 550 degree Celsius.

Volumetric- A measured based on the volume of some factor. Volumetric titration is a means of measuring unknown concentrations of water quality indicators in a sample BY DETERMINING THE VOLUME of titrant or liquid reagent needed to complete particular reaction.

Volute- The spiral shaped casing which surrounds a pump, blower, or turbine impeller and collects the liquid or gas discharged by the impeller.

Warning- The word WARNING is used to indicate a hazard level between CAUTION and DANGER.

Wastewater- A community’s used water and water carried solids that flow to a treatment plant. Storm water, surface water, and groundwater infiltration also may be included in the wastewater that enters a wastewater treatment plant. The term “sewage” usually refers to household wastes, but this word is being replaced by the term “wastewater”.

Water Cycle- The process of evaporation of water into the air and its return to earth by precipitation. This process also included transpiration from plants, groundwater movement, and runoff into rivers, streams and the ocean. Also called the “Hydrologic Cycle”.

Water Hammer- The sound like someone hammering on a pipe that occurs when a valve is opened or closed very rapidly. When a valve position is changes quickly, the water pressure in a pipe will increase and decrease back and forth very quickly. This rise and fall in pressures can cause serious damage to the system.

Weir- 1. A wall or plate placed in an open channel and used to measure that flow of water. The depth of the flow over the weir can be used to calculate the flow rate, or a chart or conversion table may be used to convert depth to flow. 2. A wall or obstruction used to control flow to ensure a uniform flow rate and avoid short circuiting.

Weir Diameter- Many circular clarifiers have a circular weir within the outside edge of the clarifier. All the water leaving the clarifier flows over this weir. The diameter of the weir is the length of a line from one edge of a weir to the opposite edge and passing through the center of the circle formed by the weir.

Weir Proportional- A specially shaped weir in which the flow through the weir is directly proportional to the head.

Wet Oxidation- A method of treating or condition sludge before the water is removed. Compressed are is blown into the liquid sludge. The air and sludge mixture is fed into a pressure vessel where the organic material is stabilized. The stabilized organic material and inert solids are then separated from the pressure vessel effluent by dewatering in lagoons or by mechanical means.

Wet Well- A compartment or tank in which wastewater is collected. The suction pipe of a pump may be connected to the wet well or a submersible pump may be located in the wet well.

Y, Growth Rate- An experimentally determined constant to estimate the unit growth rate of bacteria while degrading organic wastes.

Zoogleal- A complex population of organisms that form a “slime growth” on the trickling filter media and break down the organic matter in wastewater. These slimes consist of living organisms feeding on the wastes in wastewater, dead organisms, silt, and other debris. “Slime Growth” is a more common term.

Zoogleal- Jelly-like masses of bacteria found in both the trickling filter and activated sludge processes. These masses may be formed for or function as the protection against predators and for storage of food supplies. Also called BIOMASS.

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