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Glossary: O
Ocean Discharge Waiver:
A variance from Clean Water Act requirements for discharges into marine
waters.
Odor Threshold:
The minimum odor of a water or air sample that can just be detected after
successive dilutions with odorless water. Also called threshold odor.
Off-Site Facility:
A hazardous waste treatment, storage or disposal area that is located away from
the generating site.
Office Paper:
High grade papers such as copier paper, computer printout, and stationary almost
entirely made of uncoated chemical pulp, although some ground wood is used. Such
waste is also generated in homes, schools, and elsewhere.
Offsets:
A concept whereby emissions from proposed new or modified stationary sources are
balanced by reductions from existing sources to stabilize total emissions. (See:
bubble, emissions trading, netting)
Offstream Use:
Water withdrawn from surface or groundwater sources for use at another place.
Oil and Gas Waste:
Gas and oil drilling muds, oil production brines, and other waste associated
with exploration for, development and production of crude oil or natural gas.
Oil Desulfurization:
Widely used precombustion method for reducing sulfur dioxide emissions from
oil-burning power plants. The oil is treated with hydrogen, which removes some
of the sulfur by forming hydrogen sulfide gas.
Oil Fingerprinting:
A method that identifies sources of oil and allows spills to be traced to their
source.
Oil Spill:
An accidental or intentional discharge of oil which reaches bodies of water. Can
be controlled by chemical dispersion, combustion, mechanical containment, and/or
adsorption. Spills from tanks and pipelines can also occur away from water
bodies, contaminating the soil, getting into sewer systems and threatening
underground water sources.
Oligotrophic Lakes:
Deep clear lakes with few nutrients, little organic matter and a high
dissolved-oxygen level.
On-Scene Coordinator (OSC):
The predesignated USEPA, Coast Guard, or Department of Defense official who
coordinates and directs Superfund removal actions or Clean Water Act oil- or
hazardous-spill response actions.
On-Site Facility:
A hazardous waste treatment, storage or disposal area that is located on the
generating site.
Onboard Controls:
Devices placed on vehicles to capture gasoline vapor during refueling and route
it to the engines when the vehicle is starting so that it can be efficiently
burned.
Onconogenicity:
The capacity to induce cancer.
One-hit Model:
A mathematical model based on the biological theory that a single "hit" of some
minimum critical amount of a carcinogen at a cellular target such as DNA can
start an irreversible series events leading to a tumor.
Opacity:
The amount of light obscured by particulate pollution in the air; clear window
glass has zero opacity, a brick wall is 100 percent opaque. Opacity is an
indicator of changes in performance of particulate control systems.
Open Burning:
Uncontrolled fires in an open dump.
Open Dump:
An uncovered site used for disposal of waste without environmental controls.
(See: dump.)
Operable Unit:
Term for each of a number of separate activities undertaken as part of a
Superfund site cleanup. A typical operable unit would be removal of drums and
tanks from the surface of a site.
Operating Conditions:
Conditions specified in a RCRA permit that dictate how an incinerator must
operate as it burns different waste types. A trial burn is used to identify
operating conditions needed to meet specified performance standards.
Operation and Maintenance:
1. Activities conducted after a Superfund site action is completed to ensure
that the action is effective. 2. Actions taken after construction to ensure that
facilities constructed to treat waste water will be properly operated and
maintained to achieve normative efficiency levels and prescribed effluent
limitations in an optimum manner. 3. On-going asbestos management plan in a
school or other public building, including regular inspections, various methods
of maintaining asbestos in place, and removal when necessary.
Operator Certification:
Certification of operators of community and non-transient non-community water
systems, asbestos specialists, pesticide applicators, hazardous waste
transporter, and other such specialists as required by the USEPA or a state
agency implementing an USEPA-approved environmental regulatory program.
Optimal Corrosion Control Treatment:
An erosion control treatment that minimizes the lead and copper concentrations
at users' taps while also ensuring that the treatment does not cause the water
system to violate any national primary drinking water regulations.
Oral Toxicity:
Ability of a pesticide to cause injury when ingested.
Organic:
1. Referring to or derived from living organisms. 2. In chemistry, any compound
containing carbon.
Organic Chemicals/Compounds:
Naturally occurring (animal or plant-produced or synthetic) substances
containing mainly carbon, hydrogen, nitrogen, and oxygen.
Organic Matter:
Carbonaceous waste contained in plant or animal matter and originating from
domestic or industrial sources.
Organism:
Any form of animal or plant life.
Organophosphates:
Pesticides that contain phosphorus; short-lived, but some can be toxic when
first applied.
Organophyllic:
A substance that easily combines with organic compounds.
Organotins:
Chemical compounds used in anti-foulant paints to protect the hulls of boats and
ships, buoys, and pilings from marine organisms such as barnacles.
Original AHERA Inspection/Original Inspection/Inspection:
Examination of school buildings arranged by Local Education Agencies to identify
asbestos-containing-materials, evaluate their condition, and take samples of
materials suspected to contain asbestos; performed by USEPA-accredited
inspectors.
Original Generation Point:
Where regulated medical or other material first becomes waste.
Osmosis:
The passage of a liquid from a weak solution to a more concentrated solution
across a semipermeable membrane that allows passage of the solvent (water) but
not the dissolved solids.
Other Ferrous Metals:
Recyclable metals from strapping, furniture, and metal found in tires and
consumer electronics but does not include metals found in construction materials
or cars, locomotives, and ships. (See: ferrous metals.)
Other Glass:
Recyclable glass from furniture, appliances, and consumer electronics. Does not
include glass from transportation products (cars trucks or shipping containers)
and construction or demolition debris. (See: glass.)
Other Nonferrous Metals:
Recyclable nonferrous metals such as lead, copper, and zinc from appliances,
consumer electronics, and nonpackaging aluminum products. Does not include
nonferrous metals from industrial applications and construction and demolition
debris. (See: nonferrous metals.)
Other Paper:
For Recyclable paper from books, third-class mail, commercial printing, paper
towels, plates and cups; and other nonpackaging paper such as posters,
photographic papers, cards and games, milk cartons, folding boxes, bags,
wrapping paper, and paperboard. Does not include wrapping paper or shipping
cartons.
Other Plastics:
Recyclable plastic from appliances, eating utensils, plates, containers, toys,
and various kinds of equipment. Does not include heavy-duty plastics such as
yielding materials.
Other Solid Waste:
Recyclable nonhazardous solid wastes, other than municipal solid waste, covered
under Subtitle D of RARA. (See: solid waste.)
Other Wood:
Recyclable wood from furniture, consumer electronics cabinets, and other
nonpackaging wood products. Does not include lumber and tree stumps recovered
from construction and demolition activities, and industrial process waste such
as shavings and sawdust.
Outdoor Air Supply:
Air brought into a building from outside.
Outfall:
The place where effluent is discharged into receiving waters.
Overburden:
Rock and soil cleared away before mining.
Overdraft:
The pumping of water from a groundwater basin or aquifer in excess of the supply
flowing into the basin; results in a depletion or "mining" of the groundwater in
the basin. (See: groundwater mining)
Overfire Air:
Air forced into the top of an incinerator or boiler to fan the flames.
Overflow Rate:
One of the guidelines for design of the settling tanks and clarifiers in a
treatment plant; used by plant operators to determine if tanks and clarifiers
are over or under-used.
Overland Flow:
A land application technique that cleanses waste water by allowing it to flow
over a sloped surface. As the water flows over the surface, contaminants are
absorbed and the water is collected at the bottom of the slope for reuse.
Oversized Regulated Medical Waste:
Medical waste that is too large for plastic bags or standard containers.
Overturn:
One complete cycle of top to bottom mixing of previously stratified water
masses. This phenomenon may occur in spring or fall, or after storms, and
results in uniformity of chemical and physical properties of water at all
depths.
Oxidant:
A collective term for some of the primary constituents of photochemical smog.
Oxidation Pond:
A man-made (anthropogenic) body of water in which waste is consumed by bacteria,
used most frequently with other waste-treatment processes; a sewage lagoon.
Oxidation:
The chemical addition of oxygen to break down pollutants; e.g., destruction of
chemicals such as cyanides, phenols, and organic sulfur compounds in sewage by
bacterial and chemical means.
Oxidation-Reduction Potential:
The electric potential required to transfer electrons from one compound or
element (the oxidant) to another compound (the reductant); used as a qualitative
measure of the state of oxidation in water treatment systems.
Oxygenated Fuels:
Gasoline which has been blended with alcohols or ethers that contain oxygen in
order to reduce carbon monoxide and other emissions.
Oxygenated Solvent:
An organic solvent containing oxygen as part of the molecular structure.
Alcohols and ketones are oxygenated compounds often used as paint solvents.
Ozonation/Ozonator:
Application of ozone to water for disinfection or for taste and odor control.
The ozonator is the device that does this.
Ozone (O3):
Found in two layers of the atmosphere, the stratosphere and the troposphere. In
the stratosphere (the atmospheric layer 7 to 10 miles or more above the earth's
surface) ozone is a natural form of oxygen that provides a protective layer
shielding the earth from ultraviolet radiation. In the troposphere (the layer
extending up 7 to 10 miles from the earth's surface), ozone is a chemical
oxidant and major component of photochemical smog. It can seriously impair the
respiratory system and is one of the most wide- spread of all the criteria
pollutants for which the Clean Air Act required USEPA to set standards. Ozone in
the troposphere is produced through complex chemical reactions of nitrogen
oxides, which are among the primary pollutants emitted by combustion sources;
hydrocarbons, released into the atmosphere through the combustion, handling and
processing of petroleum products; and sunlight.
Ozone Depletion:
Destruction of the stratospheric ozone layer which shields the earth from
ultraviolet radiation harmful to life. This destruction of ozone is caused by
the breakdown of certain chlorine and/or bromine containing compounds
(chlorofluorocarbons or halons), which break down when they reach the
stratosphere and then catalytically destroy ozone molecules.
Ozone Hole:
A thinning break in the stratospheric ozone layer. Designation of amount of such
depletion as an "ozone hole" is made when the detected amount of depletion
exceeds fifty percent. Seasonal ozone holes have been observed over both the
Antarctic and Arctic regions, part of Canada, and the extreme northeastern
United States.
Ozone Layer:
The protective layer in the atmosphere, about 15 miles above the ground, which
absorbs some of the sun’s ultraviolet rays, thereby reducing the amount of
potentially harmful radiation that reaches the earth's surface.
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