P...

Packed Tower : See trickling filter.
PAH : Polycyclic aromatic hydrocarbons (rarely used as abbreviation for polyaluminum hydroxide).
Parisitism : One organism living on or in another to obtain nourishment, without provviding any benefit to the host organism.
Particulates : Liquid or solid particles such as dust, smoke, mist, or smog found in air emissions.
Parts Per Billion (ppb) : One ppb is comparable to one kernel of corn in a filled, 45-foot silo, 16 feet in diameter.
Parts Per Million (ppm) : One ppm is comparable to one drop of gasoline in a tankful of gas (full-size car).
Parts Per Trillion (ppt) : One ppt is comparable to one drop in a swimming pool covering the area of a football field 43 ft deep.
Pass Through : A discharge through the publicly owned treatment works into the waters of the United States in quantities or concentrations which, alone or in conjunction with a discharge or discharges from other sources, is a cause of a violation of any requirements of the publicly owned treatment works' national pollutant discharge elimination system permit (including an increase in the magnitude or duration of a violation).
Pathogen : A bacterial organism typically found in the intestinal tracts of mammals, capable of producing disease. Bacteria, viruses or cysts which cause disease (typhoid, cholera, dysentery) in a host (such as a person). There are many types of bacteria (non-pathogenic) which do NOT cause disease. Many beneficial bacteria are found in wastewater treatment processes actively cleaning up organic wastes.
Percolation : The movement or flow of water through soil or rocks.
Performance Bond : Cash or securities, deposited before a landfill operating permit is issued, which are held to ensure that all requirements for operating a landfill are performed. The money is returned to the owner after proper closure of the landfill is complete. If contamination or other problems appear at any time during operation, or upon closure, and are not addressed, the owner must forfeit all or part of the performance bond which is then used to cover costs of cleanup.
Peristaltic Pump : A type of positive displacement pump.
Permeability : The ease with which water, or other fluid, passes through a substance.
Permissible Exposure Limit (PEL) : Workplace exposure limits for contaminants established by OSHA.
Permit : A legal document issued by state and / or federal authorities containing a detailed description of the proposed activity and operating procedures as well as appropriate requirements and regulations. The permitting process includes provisions for public comment.
Permittee : The person holding a permit to discharge.
Person : Any individual, partnership, copartnership, firm, company, corporation, association, joint stock company, trust, estate, governmental entity or any other legal entity, or their legal representatives, agents or assigns. The masculine gender shall include feminine, the singular shall include the plural where indicated by the context.
Pesticide : Substances intended to repel, kill, or control any species designated a "pest" including weeds, insects, rodents, fungi, bacteria, or other organisms. The family of pesticides includes herbicides, insecticides, rodenticides, fungicides, and bactericides.
pH : The measure of acidity or alkalinity of a chemical solution, from 0 - 14. Anything neutral, for example, has a pH of 7. Acids have a pH less than 7, bases (alkaline) greater than 7.
Phenol : An aromatic benzene ring with a hydroxyl substituted for one hydrogen.
Phenyl- : A benzene ring named as a constituent group, C₆H₅-.
Phosphorylation : The synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP).
Photoautotrophic : Organisms which utilize inorganic carbon dioxide for protoplasm synthesis and light for an energy source.
Photochemical Pollutants : Chemicals which react photochemically (in the presence of sunlight) to destroy ozone in the stratosphere.
Photophosphorylation : The synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP) using solar energy.
Phototroph : Organisms which obtain energy from light using photooxidation.
Pin Floc : Excessive solids carryover. May occur from time to time as small suspended sludge particles in the supernatant. There are two kinds: grey -ashlike, inert, has low BOD - indicates old sludge; and brown, but a portion neither settles nor rises, has high BOD - indicates young sludge.
Plume : A concentration of contaminants in air, soil, or water usually extending from a distinct source.
Point Source : A stationary location or fixed facility such as an industry or municipality that discharges pollutants into air or surface water through pipes, ditches, lagoons, wells, or stacks; a single identifiable source such as a ship or a mine.
Pollutant : Any dredged soil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked or discharged equipment, rock, sand, cellar dirt and industrial, municipal, and agricultural waste discharged into water.
Pollution : Any substances in water, soil, or air that degrade the natural quality of the environment, offend the senses of sight, taste, or smell, or cause a health hazard. The usefulness of the natural resource is usually impaired by the presence of pollutants and contaminants.
Pollution Prevention : Actively identifying equipment, processes, and activities which generate excessive wastes or use toxic chemicals and then making substitutions, alterations, or product improvements. Conserving energy and minimizing wastes are pollution prevention concepts used in manufacturing, sustainable agriculture, recycling, and clean air / clean water technologies.
Polychlorinated Biphenyls (PCBs) : A group of toxic, persistent chemicals used in electrical transformers and capacitors for insulating purposes, and in gas pipeline systems as a lubricant. The sale and new use of PCBs were banned by law in 1979.
Polymer : A chemical formed by the union of many monomers (a molecule of low molecular weight). Polymers are used with other chemical coagulants to aid in binding small suspended particles to form larger chemical flocs for easier removal from water. All polyelectrolytes are polymers, but not all polymers are polyelectrolytes.
Polyculture : Fish farming in which 2 or more compatible or symbiotic species of fish are grown together. Also known as Multiculture.
Potable Water : Raw or treated water that is considered safe to drink.
Potentially Responsible Party (PRP) : Any individual or company that is potentially responsible for or has contributed to a spill or other contamination at a Superfund site. Whenever possible, EPA requires PRPs to clean up sites they have contaminated.
Precipitation : The falling to earth of condensed water vapor in the form of rain, snow, sleet or hail.
Predation : One species benefits at the expense of another.
Preliminary Treatment : The removal of metal, rocks, rags, sand, eggshells, and similar materials which may hinder the operation of a treatment plant. Preliminary treatment is accomplished by using equipment such as racks, bar screens, comminutors, and grit removal systems.
Pretreatment : Methods used by industry and other non-household sources of wastewater to remove, reduce, or alter the pollutants in wastewater before discharge to a POTW.
Pretreatment Facility : Industrial wastewater treatment plant consisting of one or more treatment devices designed to remove sufficient pollutants from wastewaters to allow an industry to comply with effluent limits established by the US EPA General and Categorical Pretreatment Regulations or locally derived prohibited discharge requirements and local effluent limits. Compliance with effluent limits allows for a legal discharge to a POTW.
Pretreatment Program : This term means an administrative and regulatory program established and implemented by the City of Bedford that meets the requirements and criteria of the applicable federal and state pretreatment regulations and which has been approved by the approval authority.
Pretreatment Requirements : Any substantive or procedural requirement related to pretreatment imposed on a user, other than a pretreatment standard.
Pretreatment Standards : All applicable federal rules and regulations (including specifically those regulations found in 40 CFR, Chapter I, Subchapter N, Parts 405 through 471) implementing Section 307, the Federal Water Pollution Control Act and the Clean Water Act of 1977, including all amendments, as well as nonconflicting state and local standards. In case of conflict of regulations, the most stringent thereof shall be applied.
Primary Standards : Required drinking water quality standards related directly to human health. These standards are required and enforceable by the US EPA.
Primary Treatment : First stage of wastewater treatment in which solids are removed by screening and settling.
Procaryotic Organisms : Organisms which do not have a cellular membrane. Microorganisms which do NOT have an organized nucleus surrounded by a nuclear membrane. Bacteria and blue-green algae fit in this category.
Process Wastewater : Any water which comes into contact with any raw material, product, by-product, or waste.
Producers : Autotrophic organisms which produce protoplasm using inorganic carbon and energy from the sun.
Properly Shredded Garbage : The wastes from the preparation, cooking, and dispensing food that have been shredded to such a degree that all particles will be carried under the flow conditions normally prevailing in public sewers, with no particles greater than one-half (1/2) inch in any dimension.
Protozoa : A group of motile microscopic animals (usually single-celled and aerobic) that sometimes cluster into colonies and often consume bacteria as an energy source.
Psychrophilic Bacteria : Bacteria whose optimum temperature range is between 0 and 20 C (32 to 68 C), such as those found in Alken Clear-Flo® 7018.
Public Comment Period : The time allowed for the members of an affected community to express views and concerns regarding an action proposed to be taken by EPA, such as a rulemaking, permit, or Superfund remedy selection.
Public Water System : Any water system that regularly supplies piped water to the public for consumption, serving at least an average of 25 individuals per day for at least 60 days per year, or has at least 15 service connections.
Publicly Owned Treatment Works (POTW) : A municipal or public service district sewage treatment system.
Putrefaction : Biological decomposition of organic matter with the production of ill-smelling products associated with anaerobic conditions.

Q...

Quality Assurance / Quality Control : A system of procedures, checks, audits, and corrective actions to ensure that all technical, operational, monitoring, and reporting activities are of the highest achievable quality.
Quench Tank : A water-filled tank used to cool incinerator residue or hot materials from industrial processes.

R...

Rack : Evenly spaced parallel metal bars or rods located in the influent channel to remove rags, rocks, and cans from wastewater.
Radioactive Waste : Any waste that emits energy as rays, waves, or streams of energetic particles. Radioactive materials are often mixed with hazardous waste, usually from nuclear reactors, research institutions, or hospitals.
Radon : A colorless, naturally occurring gas formed by radioactive decay of radium atoms. Radon accumulating in basements and other areas of buildings without proper ventilation has been identified as a leading cause of lung cancer.
RASVSS : Return activated sludge volatile suspended solids.
Rate Base : The value of utility property used in computing an authorized rate of return as authorized by law or a regulatory commission.
Raw Water : Intake water prior to any treatment or use.
Reactive Waste : A waste which ; (1) reacts violently with water, (2) forms potentially explosive mixtures with water, (3) is normally unstable, (4) contains cyanide or sulfide in sufficient quantity to evolve toxic fumes at high or low pH, (5) is capable of exploding if heated under pressure, or (6) is an explosive compound listed in Department of Transportation (DoT) regulations. One of EPA's four hazardous waste properties.
Reactivity : Refers to those hazardous wastes that are normally unstable and readily undergo violent chemical change but do not explode.
Reaeration : The dissolving of molecular oxygen from the atmosphere into the water.
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.
Receiving Waters : A river, lake, ocean, stream, or other body of water into which wastewater or treated effluent is discharged.
Receiving Water Quality Standards : Standards which require a discharger to maintain a certain quality level in the receiving water.
Recharge Area : An area of land where there is a net annual transfer of water from the surface to ground water; where rainwater soaks through the earth to reach an aquifer.
Recycle : The use of water or wastewater within (internally) a facility before it is discharged to a treatment system.
Recycling : Reusing materials and objects in original or changed forms rather than discarding them as wastes.
Record of Decision (ROD) : A public document that explains which cleanup alternative was selected for a Superfund site.
Red Bag Waste : See definition for Medical Waste.
REDOX (Biological Reductions / Oxidations) : These reactions usually require enzymes to mediate the electron transfer. The sediment in the bottom of a lake, sludge in a sewerage works or septic tank will have a very low redox potential and will likely be devoid of any oxygen. This sludge or waste water will have a very high concentration of reductive anaerobic bacteria, indeed the bulk of the organic matter may in fact be bacteria. As the concentration of oxygen increases the oxidation potential of the water will increase. A low redox potential or small amount of oxygen is toxic to anaerobic bacteria, therefore as the concentration of oxygen and redox potential increases the bacterial population changes from reductive anaerobic bacteria to oxidative aerobic bacteria. Measurement of REDOX potential is also referred to as ORP.
Reducing Agent : Any substance, such as the base metal (iron) or the sulfide ion that will readily donate (give up) electrons. The opposite of an oxidizing agent.
Reference Dose (RfD) : The particular concentration of a chemical that is known to cause health problems. A standard that also may be referred to as the acceptable daily intake.
Refine : To remove impurities.
Refractory Materials : Material difficult to remove entirely from wastewater such as nutrients, color, taste, and odor-producing substances and some toxic materials.
Refuse : All forms of solid waste.
Refuse Derived Fuel : A fuel derived from the combustible portion of municipal solid waste. The fuel is often processed into small briquettes, similar in size to charcoal.
Regional Response Team (RRT) : There are 13 RRTs, one for each of 10 federal regions, plus one for Alaska, one for the Caribbean, and one for the Pacific Basin. Each RRT maintains a Regional Contingency Plan and has state and federal government representation. EPA and the US Coast Guard cochair the RRTs. Like the NRT, RRTs are planning, policy, and coordinating bodies and do not respond directly to pollution incidents but do provide assistance when requested by the federal On-Scene Coordinator. RRTs also provide assistance to SERCs and LEPCs in local preparedness, planning, and training for emergency response.
Registration : Formal listing with EPA of a new pesticide before sale or distribution. EPA is responsible for pre-market licensing of pesticides on the basis of data demonstrating no unreasonable adverse health or environmental effects when applied according to approved label directions.
Release : Any spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment of a hazardous or toxic chemical, or extremely hazardous substance.
Remedial Action : The actual construction or clean-up phase of a Superfund site cleanup.
Replacement : Expenditures for obtaining and installing equipment, accessories, or appurtenances which are necessary during the useful life of the treatment works to maintain the capacity and performance for which such works were designed and constructed. The term "operation and maintenance" (O&M) includes replacement.
Replacement Costs : The costs as of certain date of a property which can render similar service (but which need not be of the same structural form) as the property to be replaced. Replacement is an incremental element of operating costs and is variable depending upon levels of expenditures for maintenance. The statutory definition of the term means expenditures for obtaining and installing equipment, accessories or appurtenances during the useful life of the treatment works necessary to maintain the capacity and performance for which they were designed and constructed. It is not a capital cost and does not increase the book value of an asset.
Reportable Quantity (RQ) : Amount of a hazardous or extremely hazardous substance that, if released into the environment, must be reported to the NRC, the SERC, and the LEPC under Section 304 of EPCRA.
Residential : Shall include all dwelling units such as detached, semidetached, rowhouses, mobile homes and multifamily dwellings.
Residual Risk : The risk associated with pollutants after the application of maximum achievable control technology or MACT.
Resource Recovery : The extraction of useful materials or energy from solid waste. Such materials can include paper, glass, and metals that can be reprocessed for re-use. Resource recovery also is employed in pollution prevention.
Respiration : Energy production in which oxygen is the terminal electron acceptor, i.e. oxidation to produce energy where oxygen is the oxidizing agent. The energy producing process of breathing, by which an organism supplies its cells with oxygen and relieves itself of carbon dioxide. A type of heterotrophic metabolism that uses oxygen in which 38 moles of ATP are derived from the oxidation of 1 mole of glucose, yielding 380,000 cal. (An additional 308,000 cal is lost as heat.)
Respiration Rate (RR) : The weight of oxygen utilized by the total weight of MLSS in a given time.
Responsiveness Summary : A summary of oral and written comments received by EPA during a public comment period on key documents or actions proposed to be taken, and EPA s response to those comments.
Return Activated Sludge (RAS) : Settled activated sludge that is collected in the secondary clarifier and returned to the aeration basin to mix with incoming raw settled wastewater.
Reversible Reaction : A reaction in which the reactant(s) proceed to product(s), but the products react at an appreciable rate to reform reactant(s).
Rhizosphere : Soil surrounding plant roots.
Risk : A measure of the chance that damage to life, health, property, or the environment will occur.
Risk Assessment : A process to determine the increased risk from exposure to environmental pollutants together with an estimate of the severity of impact. Risk assessments use specific chemical information plus risk factors.
Risk Communication : The process of exchanging information about levels or significance of health or environmental risk.
Risk Factor : A characteristic (e.g., race, sex, age, obesity) or variable (e.g., smoking, exposure) associated with increased chance of toxic effects. Some standard risk factors used in general risk assessment calculations include average breathing rates, average weight, and average human life span.
Rodenticide : A pesticide or other agent used to kill rats and otherrodents or to prevent them from damaging food, crops, or forage.
Rotating Biological Contactor (RBC) : An attached culture wastewater treatment system.
R / O Unit : Reverse osmosis unit for water purification in small aquariums and miniature yard-ponds, utilizes a membrane under pressure to filter dissolved solids and pollutants from the water. Two different filter membranes can be used: the CTA (cellulose triacetate) membrane is less expensive, but only works with chlorinated water and removes 50-70% of nitrates, and the TFC membrane, which is more expensive, removes 95% of nitrates, but is ruined by chlorine. R/O wastes water and a system that cleans 100 gallons a day will cost from $ 400 to $ 600 with membrane replacement adding to the cost. A unit that handles 140 gallons a day will cost above $ 700.00.
Runoff : The water that flows overland to lakes or streams during and shortly after a precipitation event.