G...

Garbage : Food waste (animal and vegetable) resulting from the handling, storage, packaging, sale, preparation, cooking, and serving of foods.
Gasification : The conversion of soluble and suspended materials into gas during 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.
Gas Stripping : Gas transfer of an undesirable gas from a water stream to the atmosphere.
General Reporting Facility : A facility having one or more hazardous chemicals above the 10,000-pound Threshold Planning Quantity. These facilities must file Material Safety Data Sheets and emergency inventory information with the SERC, LEPC, and local fire departments.
Generation Time : The time required for a given population to double in size. This time can be as short as 20 minutes or as long as a week.
Generator : A facility or mobile source that emits pollutants into the air; any person who produces a hazardous waste that is listed by EPA and therefore subject to regulation.
Genetic Engineering : A process of inserting new genetic information into existing cells in order to modify an organism for the purpose of changing particular characteristics.
Global Warming : The long-term warming of the plant due to increases in greenhouse gases which trap reflected light preventing it from exiting to space. See also definition for Climate Change.
Glyoxylate Cycle : A modification of the Krebs cycle, which occurs in some bacteria. Acetyl coenzyme A is generated directly from oxidation of fatty acids or other lipid compounds.
Governmental : [The word "governmental"] shall include legislative, judicial, administrative and regulatory activities of federal, state, and local governments.
Grab Sample : A single sample of soil or of water taken without regard to time or flow.
Gram Negative : Bacteria cells which lose the crystal violet during the decolorizing step and are then colored by the counterstain. Pseudomonas and Thiobacillus are examples of gram negative strains.
Gram Positive : Bacterial cells which retain the crystal violet stain during a staining procedure. Most strains of bacilli are gram positive.
Grantee : A municipality that has executed a federal grant agreement.
Greenhouse Effect : See definition for Climate Change.
Greenhouse Gases : Gases which trap solar radiation. Of the solar energy entering the earth's atmosphere a portion is reflected back and a portion penetrates onto the earth's surface. The portion reflected back from the earth's surface is at a different wavelength that when it entered. Carbon dioxide and other gases, which pass solar radiation, absorb this reflected radiation, increasing the earth's temperature. This is much like a greenhouse, hence the name.
Grit : The heavy material present in wastewater, such as sand coffee grounds, eggshells, gravel and cinders.
Ground Water : Water found below the surface of the land, usually in porous rock formations. Ground water is the source of water found in wells and springs and is used frequently for drinking.

H...

Halophilic or Halotolerant : Bacteria which thrive in a highly salt environment, up to 25% NaCl.
HAPs : Hazardous air pollutants.
Hardness : The sum of the divalent cation concentrations expressed as meq/L or mg calcium carbonate per liter (mg CaCO₃ / L). It is important because hard waters require increased amounts of soap for bathing or washing clothes and because of scale formation on piping, cooking vessels, water heaters, boilers, heat exchangers, etc.
Hazard Communication Standard : An OSHA regulation that requires chemical manufacturers, suppliers, and importers to assess the hazards of the chemicals they make, supply, or import, and to inform employers, customers, and workers of these hazards through a Material Safety Data Sheet.
Hazardous Chemical : EPA s designation for any hazardous material that requires a Material Safety Data Sheet. Such substances are capable of producing adverse physical effects (fire, explosion, etc.) or adverse health effects (cancer, dermatitis, etc.).
Hazardous Waste : A subset of solid wastes that pose substantial or potential threats to public health or the environment and meet any of the following criteria ; (a) is specifically listed as a hazardous waste by EPA; exhibits one or more of the characteristics of hazardous wastes (ignitability, corrosiveness, reactivity, and/or toxicity) and (b) is generated by the treatment of hazardous waste; or is contained in a hazardous waste.
Hazardous Waste Landfill : A specially permitted, excavated or engineered area in which hazardous waste is deposited and covered. Proper protection of the environment from the materials to be deposited in such a landfill requires careful site selection, the cataloging of types of wastes, good design (including a liner and a leachate collection and treatment system), proper operation, and thorough final closure.
Headworks : The facilities where wastewater enters a wastewater treatment plant. The headworks may consist of bar screens, comminutors, a wet well and pumps.
Health Assessment : An evaluation of available data on existing or potential risks posed by a Superfund site. Every site on the National Priorities List has a health assessment prepared by the Agency for Toxic Substances and Disease Registry (see Government Agency section).
Heavy Metal : A common hazardous waste; can damage organisms at low concentrations and tends to accumulate in the food chain.
Herbicide : A pesticide designed to control or kill plants, weeds, or grasses. Almost 70% of all pesticide used by farmers and ranchers are herbicides. These chemicals have wide-ranging effects on non-target species (other than those the pesticide is meant to control).
Heterotrophic : A group of organisms which obtain carbon for synthesis from other organic matter or proteins.
High Strength Wastewater : Wastewater or sewage discharged into the public sewer in which one or more of the following concentrations are exceeded ; (1) BOD = 240 mg / L and (2) Suspended solids = 240 mg / L.
Hindered (Zone) Settling : Settling in which particle concentrations are sufficient that particles interfere with the settling of other particles. Particles settle together as a body or structure with the water required to traverse the particle interstices.
Holding Tank Waste : Any waste from holding tanks such as vessels, chemical toilets, campers, trailers, septic tanks, and vacuum pump tank trucks.
Household or Domestic Waste : Solid waste, composed of garbage and rubbish, which normally originates from residential, private households, or apartment buildings. Domestic waste may contain a significant amount of toxic or hazardous waste from improperly discarded pesticides, paints, batteries, and cleaners.
House Sewer : The pipeline connecting the house and drain and the septic tank.
HRT : Hydraulic retention time.
Humus : The dark organic material in soils, produced by the decomposition of soils. The matter that remains after the bulk of detritus has beenconsumed (leaves, roots). Humus mixes with top layers of soil (rock particles), supplies some of the nutrients needed by plants -increases acidity of soil; inorganic nutrients more soluble under acidic conditions, become more available, EX. wheat grows best at pH 5.5-7.0. Humus modifies soil texture, creates loose, crumbly texture, that allows water to soak in and nutrients retained; permits air to be incorporated into soil.
Hydraulic Gradient : The direction of ground water flow due to changes in the depth of the water table.
Hydraulic Loading : Hydraulic loading refers to the flows (MGD or m³ / day) to a treatment plant or treatment process.
Hydrocarbons : Chemicals that consist entirely of hydrogen and carbon. Hydrocarbons contribute to air pollution problems like smog.
Hydrogen Sulfide Gas : Hydrogen sulfide is a gas with a rotten egg odor. This gas is produced under anaerobic conditions. Hydrogen sulfide is particularly dangerous because it dulls your sense of smell so that you don't notice it after you have been around it for a while and because the odor is not noticeable in high concentrations. The gas is very poisonous to your respiratory system, explosive, flammable, and colorless.
Hydrolysis : The process in which carbohydrates and starches are simplified into organic soluble organics, usually by facultative anaerobes.
Hygroscopic : Absorbing or attracting moisture from the air.
Hypolimnion : The lower layer of a lake.

I...

Identification Code or EPA I.D. Number : The unique code assigned to each generator, transporter, and treatment, storage, or disposal facility by EPA to facilitate identification and tracking of hazardous waste. Superfund sites also have assigned I.D. numbers.
Impoundment : A body of water or sludge confined by a dam, dike, floodgate, or other barrier.
Improvements : Buildings, other structures, and other attachments or annexations to land which are intended to remain so attached or annexed, such as sidewalks, trees, drives, tunnels, drains, and sewers. Sidewalks, curbing, sewers, and highways are sometimes referred to as "betterments", but the term "improvements" is preferred.
In Situ Treatment : Treatment of a waste in place, as opposed to pumping or digging the waste up and then treating it.
Incident Command System (ICS) : An organizational scheme wherein one person, normally the Fire Chief, takes charge of an integrated, comprehensive emergency response. This commander is backed by an Emergency Operations Center which provides support, resources, communications, and advice.
Incineration : The destruction of solid, liquid, or gaseous wastes by controlled burning at high temperatures. Hazardous organic compounds are converted to ash, carbon dioxide, and water. Burning destroys organics, reduces the volume of waste, and vaporizes water and other liquids the wastes may contain. The residue ash produced may contain some hazardous material, such as non-combustible heavy metals, concentrated from the original waste.
Incinerator : A furnace for the routine burning of waste materials using controlled flame combustion.
Incompatible Waste : A waste unsuitable for mixing with another waste or material because of reactivity hazards.
Indirect Discharge : The introduction of pollutants from a non-domestic source into a publicly owned wastewater treatment system. Indirect dischargers can be commercial or industrial facilities who must pre-treat their wastes before discharge into local sewers.
Indoor Air : Breathing air inside a habitable structure, often highly polluted because of lack of exchange with fresh oxygen from outdoors. Solvents, smoke, paints, furniture glues, carpet padding, and other synthetic chemicals trapped inside contribute to an often unhealthy environment.
Industrial User : Any user that is a source of an indirect discharge.
Industrial Waste : Unwanted materials produced in or eliminated from an industrial operation and categorized under a variety of headings, such as liquid wastes, sludge, solid wastes, and hazardous wastes.
Inert Ingredients : Substances that are not active, such as water, petroleum distillates, talc, corn meal, or soaps. When discussing pesticides, inert ingredients do not attack a particular pest, but some are chemically or biologically active, causing health and environmental problems.
Infectious Disease : A disease caused by pathogenic organisms.
Infectious Waste : See definition for Medical Waste.
Infiltration : The movement of water from the surface of the land through the unsaturated zone and into the groundwater. This occurs during and immediately after precipitation events. It can also occur at the bottom of lakes and rivers.
Inflow : Water other than wastewater that enters a sewer system (including sewer service connections) from sources such as, but not limited to, roof leaders, cellar drains, yard drains, area drains, drains from springs and swampy areas, manhole covers, cross connections between storm sewers and sanitary sewers, catch basins, cooling towers, storm waters, surface runoff, street wash waters, or drainage. Inflow does not include, and is distinguished from, infiltration.
Influent : The fluid entering a system, process, tank, etc. An effluent from one process can be an influent to another process.
Innovative Technology : New or inventive methods to treat hazardous wastes, conserve energy, or prevent pollution.
Inoculate : To introduce a seed culture into a system, such as with the addition of ALKEN CLEAR-FLO® cultures.
Inorganic Waste : Waste material such as sand, salt, iron, calcium, and other mineral materials which are only slightly affected by the action of organisms. Inorganic wastes are chemical substances of mineral origin; whereas organic wastes are chemical substances usually of animal or plant origin.
Insecticide : A pesticide compound specifically used to kill or prevent the growth of insects.
Institutional : [The word "institutional"] shall include social, charitable, religious, and educational activities such as schools, churches, hospitals, nursing homes, penal institutions, and similar institutional users.
Integrated Pest Management (IPM) : A combination of biological, cultural, and genetic pest control methods with use of pesticides as the last resort. IPM considers a targeted species' life cycle and intervenes in reproduction, growth, or development to reduce the population. Land use practices are examined for possible change; other animals, birds, or reptiles in the ecosystem are used as natural predators.
Interceptor Sewer Main : A sewer main designed and constructed to intercept or receive sewage from all collector sewers and laterals within one or more drainage areas and carry it to a larger interceptor sewer or the point of disposal.
Interface : The common boundary layer between two substances such as between water and a solid (metal) or between water and a gas (air) or between a liquid (water) and another liquid (oil).
Interference : A discharge which, alone or in conjunction with a discharge or discharges from other sources, both ; (1) inhibits processes or operations, or its sludge processes, use, or disposal; and (2) therefore is a cause of a violation of any requirement of the publicly owned treatment works national pollutant discharge elimination system permit (including an increase in the magnitude or duration of a violation) or of the prevention of sewage sludge use or disposal. Requirements include, but are not limited to, those necessary to comply with the following statutory provisions and regulations over permits issued thereunder (or more stringent state or local regulations):Section 405 of the Clean Water Act, the Solid Waste Disposal Act (including Title II, more commonly referred to as the Resource Conservation and Recovery Act, and including state regulations contained in any state sludge management plan prepared pursuant to Subtitle D of the Solid Waste Disposal Act), the Clean Air Act, the Toxic Substances Control Act, and the Marine Protection Research and Sanctuaries Act.
Interspecies : Between two different species, such as tomato and weeds.
Interstate Commerce : A clause of the United States Constitution which reserves to the federal government the right to regulate the conduct of business across state lines. Under this clause, the U.S. Supreme Court has ruled that states may not restrict the disposal of wastes originating out-of-state more than that of waste originating in-state.
Intraspecies : Within same species; Elk vs. Elk.
Inversion : An atmospheric condition caused by increasing temperature with elevation, resulting in a layer of warm air preventing the rise of cooler air trapped beneath. This condition prevents the rise of pollutants that might otherwise be dispersed. Trapping pollutants near the ground increases ozone to harmful levels.
Ion Exchange : An adsorption process in which one ion is exchanged for another ion of like charge. There is an equivalence of exchanged charge.
Ionization : The process of adding electrons to, or removing electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, and nuclear radiation can cause ionization.
Irradiated Food : Food that has been briefly exposed to radioactivity (usually gamma rays) to kill insects, bacteria, and mold. Irradiated food can be stored without refrigeration or chemical preservatives and has a long "shelf life."
Irreversible Reaction : A reaction in which the reactant(s) proceed to product(s), but the products react at an appreciable rate to reform reactant(s).
Irritant : A substance that can cause irritation of the skin, eyes, or respiratory system. An irritant can cause an acute effect from a single high-level exposure, or chronic effects from repeated, low-level exposures. Some examples of irritants are chlorine, nitric acid, and various pesticides.
Isomers : Two or more different compounds with the same chemical formula but different structure and characteristics.