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Definition of Terms - P

package treatment plant
A small pre-engineered 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.
Palmer-Bowlus flume
A type of Venturi flume that uses a constricted throat to measure flow in partially full pipes.
parallel operation
When wastewater being treated is split and a portion flows to one treatment unit while the remainder flows to another similar treatment unit.
parameter
A quantity or characteristic which describes physical, chemical or biological conditions, such as temperature, dissolved oxygen, color, count, species composition on condition of aquatic organisms, stream flow, velocity and area of channel cross-section.
Parshall flume
A calibrated device developed by Parshall for measuring the flow of liquid in an open conduit. It consists essentially of a contracting length, a throat and an expanding length. At the throat is a sill over which the flow passes at critical depth. The upper and lower heads are measured at a definite distance from the sill.
particles
Generally, discrete solids suspended in water or wastewater, which can vary widely in size, shape, density and charge. Colloidal and dispersed particles are artificially agglomerated by processes of coagulation and flocculation.
particulate matter-10 (PM-10)
A standard for measuring a major air pollutant -- consisting of tiny solid or liquid particles of soot, dust, aerosols, fumes, and mists suspended in the atmosphere -- over 10 micrometers in diameter. The size of the particles (10 microns or smaller) allows them to easily enter the air sacs deep in the lungs where they may be deposited to result in adverse health effects. These smaller particles particularly affect sensitive population groups such as children and people with respiratory diseases.
partnering
A formal team building process among diverse entities that are working towards a common goal. The terminology has developed around the construction industry wherein the owner, contractor, engineer, and construction manager staff spend time at the start of a project developing mutual goals and objectives to improve project communications and responsiveness that will result in fewer problems and claims during the project. The team building is done under the direction of a facilitator.
parts per million (ppm)
The number of weight or volume units of a minor constituent present with each one million units of a solution or mixture. In water-related issues the more specific term milligrams per liter (mg/L) is preferred. In air-related issues the more specific term milligrams per litervolume (mg/Lv) is preferred.
pasture
Land on which animals feed directly on feed crops.
pathogenic bacteria
Bacteria that cause disease in the host organism by their parasitic growth.
pathogens
Organisms capable of producing diseases in humans or animals.
peak demand
The maximum momentary load placed on a water or wastewater plant or pumping station or on an electric generating plant or system. This is usually the maximum average load in one hour or less, but may be specified as instantaneous or for some other short time period.
peak stream flow
The maximum expected flow of surface water from a tributary watershed for a given recurrence interval.
peer review
The independent review of work by other experts and/or professionals within the same academic or professional fields.
percentage reduction
The ratio of material removed from water or wastewater by treatment to the material originally present, expressed as a percentage. When percentages exceed 99.9%, the term "log removal" is preferred.
perched groundwater
A body of unconfined ground water separated from the zone of saturation by a portion of the unsaturated zone. Such perched water can either be permanent or ephemeral.
percolation
(1) The flow or trickling of a liquid downward through a contact or filtering medium. The liquid may or may not fill the pores of the medium. Also called filtration. (2) The movement or flow of water through the interstices or the pores of a soil or other porous medium. (3) The movement of groundwater in streamline flow in any direction through small interconnected and saturated interstices of rock or earth, principally of capillary size. (4) The water lost from an unlined conduit through its sides and bed.
performance bond
A pledge from a surety to pay the bond amount to the Obligee (owner or contractor) in the event of a default in performance of contractual obligations.
permeability
(1) The property of a material that permits appreciable movement of water through it when it is saturated and the movement is actuated by hydrostatic pressure of the magnitude normally encountered in natural subsurface water. Perviousness is sometimes used in the same sense as permeability. (2) The ability of natural and artificial materials to transmit fluids.
pervious
Possessing a texture that permits water to move through perceptibly under the head differences ordinarily found in subsurface water.
pesticide
Any chemical or biological agent that kills plants or animal pests. Herbicides, insecticides, nematocides, miticides, algicides, etc., are all pesticides.
pH
A measure of the hydrogen-ion concentration in a solution, expressed as the logarithm (base ten) of the reciprocal of the hydrogen-ion concentration in gram moles per liter. On the pH scale (0-14), a value of 7 at 25 °C represents a neutral condition. Decreasing values, below 7, indicate increasing hydrogen-ion concentration (acidity); increasing values, above 7, indicate decreasing hydrogen-ion concentration (alkalinity) .
phased construction
An incremental approach to design or construction. Each overlapping or sequential phase or element would have a defined scope of work and would be considered as a separate project.
phenolic compounds
Hydroxy derivatives of benzene. The simplest phenolic compound is phenol, C6H5OH.
phenol wastes
Industrial wastes containing phenols, derived chiefly from coking processes and oil refineries.
phosphorus
An essential chemical element and nutrient for all life forms. Occurs in orthophosphate, pyrophosphate, tripolyphosphate and organic phosphate forms. Each of these forms and their sum, total phosphorus, is expressed as mg/L elemental phosphorus.
photosynthesis
The synthesis of complex organic materials, especially carbohydrates, from carbon dioxide, water and inorganic salts, with sunlight as the source of energy and with the aid of a catalyst such as chlorophyll, results in the production of oxygen.
physical adsorption
The accumulation or concentration of substances (adsorbate) at a surface or interface with another substance (adsorbent) by physical attraction and interaction.
physical analysis
The examination of water and wastewater to determine physical characteristics such as temperature, turbidity, color, odors, taste.
physical assets
Permanent property of a physical nature, such as lands, buildings, mineral deposits, wells, reservoirs, plant equipment of all kinds, utensils, furnishings, rolling stock and merchandise, intended for immediate use and permanent improvements. Also called tangible assets.
physical-chemical treatment
Treatment of wastewaters by unit processes other than those based on microbiological activity. Unit processes commonly included are: precipitation with coagulants, flocculation with or without chemical flocculants, filtration, adsorption, chemical oxidations, air stripping, ion exchange, reverse osmosis and several others.
physical parameters
Any measurable physical characteristic of a substance including, but not limited to, temperature, electrical conductivity, pH, and specific gravity.
physical waste treatment process
Racks, screens, comminutors, sedimentation, flotation, and filtration. Chemical or biological reactions are not an important part of the process.
phytoplankton
Plankton consisting of plants, such as algae.
piezometer
An instrument for measuring pressure head in a conduit, tank or soil. It usually consists of a small pipe or tube tapped into the side of the container, with its inside end flush with, and normal to, the water face of the container, and connected with a manometer pressure gage, mercury or water column or other device for indicating pressure head.
pilot-plant studies
Evaluation, on a scale larger than bench-scale but smaller than full-scale, of the amenability of wastewater to treatment with particular operations or processes.
pipe bedding
The surface and/or material on which pipe rests in a ditch.
Pitot tube
A device for measuring the velocity of flowing fluid by using the velocity head of the stream as an index of velocity. It consists essentially of an orifice held to point upstream and connected with a tube in which the impact pressure due to velocity head may be observed and measured. It also may be constructed with an upstream and downstream orifice, or with an orifice pointing upstream to measure the velocity head or pressure and piezometer holes in a coaxial tube to measure the static head or pressure, in which case the difference in pressure is the index of velocity.
plankton
(1) Small, usually microscopic, plants (phytoplankton) and animals (zooplankton) in aquatic systems. (2) The aggregate of passively floating, drifting, weakly motile organisms in a body of water.
plant hydraulic capacity
The level of flow into a plant above which the system is hydraulically overloaded.
plant-scale studies
Full-scale evaluation of whether or not a particular wastewater is amenable to treatment with a particular operation or processes.
plastic media
Honeycomb-like products with high surface area to volume ratios, manufactured from plastics of various compositions, that are used in trickling filters in place of crushed stone. The product is available in: (1) large modules, fabricated from sheets, that may be cut to size on site, and (2) small discrete pieces to be loosely packed in the filter bed.
plate count
Number of colonies of bacteria grown on selected solid media at a given temperature and incubation period, usually expressed in number of bacteria per milliliter of sample.
plate press
A filter press consisting of a number of parallel plate units lined with filter cloth which rests on drainage channels in the plates. The pressure is exerted by the pumping of solids into chambers so created between the cloths. The operation is carried out in batches.
plug flow
Flow in which fluid particles are discharged from a tank or pipe in the same order in which they entered it. The particles retain their discrete identities and remain in the tank for a time equal to the theoretical detention time.
plume
The visible or measurable discharge of a contaminant from a given point of origin.
pluviometer
A rain gauge.
pneumatic ejector
A device for raising wastewater, sludge or other liquid by alternately admitting it through an inward swinging check valve into the bottom of an airtight pot and then discharging it through an outward swinging check valve by admitting compressed air to the pot above the liquid.
point source
Any discernible, confined or discrete conveyance from which pollutants are or may be discharged, including, but not limited to, any pipe, ditch, channel, tunnel, conduit, well, container, rolling stock, concentrated animal feeding operation or vessel or other floating craft.
pollutant
Waste discharged into water, including dredged soil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, discarded equipment, and rock.
pollution
(1) Specific impairment of water quality by agricultural, domestic or industrial wastes (including thermal and atomic wastes) to a degree that has an adverse effect upon any beneficial use of water. (2) The addition to a natural body of water of any material which diminishes the optimal economic use of the water body by the population which it serves, and has an adverse effect on the surrounding environment.
pollutant load
(1) The quantity of material in a waste stream which requires treatment or exerts an effect on the receiving system. (2) The quantity of material carried in a body of water which exerts a detrimental effect on some subsequent use of that water.
polychlorinated biphenyl (PCB)
One of a class of aromatic organic compounds with two six-carbon unsaturated rings, with chlorine atoms substituted on each ring and more than two such chlorine atoms per molecule of PCB. PCBs are very stable, resist both chemical and biological degradation, and are toxic to many biological species.
polymer
Synthetic organic compound with high molecular weight and composed of repeating chemical units (monomers); they may be polyelectrolytes, such as water-soluble flocculants or water-insoluble ion exchange resins, or insoluble uncharged materials, such as those used for plastic or plastic-lined pipe and plastic trickling filter media.
polynuclear aromatic hydrocarbon (PAHs)
One of several classes of petroleum-based, persistent organic pollutants that are released into the environment in large quantities due in large part to human activities. Some are known to be potent carcinogens in mammals. PAHs are primarily combustion byproducts and are present in urban runoff.
polyvinyl chloride (PVC)
An artificial polymer made from vinyl chloride monomer (CH2:CHCl) and frequently used in pipes, sheets and vessels for transport, containment and treatment in water and wastewater facilities.
pond
A body of water of limited size, either naturally or artificially confined and usually smaller than a lake.
pool
(1) A small and rather deep body of relatively quiet water, as a pool in a stream. (2) A small body of standing or stagnant water; a puddle.
population equivalent
The estimated population which would contribute a given amount of a specific waste parameter (BOD5, suspended solids, flow); usually applied to industrial waste. Domestic wastewater contains material that consumes, on the average, 0.17 lb (0.08 kg) of oxygen per capita per day, as measured by the standard BOD test. For example, if an industry discharges 1,000 pounds (454 kg) of BOD per day, its waste is equivalent to the domestic wastewater from 6,000 people (1,000/0.17 = approx 6,000).
Porter-Cologne Water Quality Control Act
The California law (Water Code 1300 and following) which contains the principal laws governing the discharge of wastewaters in the State.
post-aeration
The addition of air to plant effluent to increase the oxygen concentration of the treated wastewater.
postchlorination
The application of chlorine to water or wastewater subsequent to any treatment.
post treatment
Treatment of finished water or wastewater for the purpose of further enhancing or protecting its quality.
potable water
Water that does not contain objectionable pollution, contamination, minerals or infective agents and is considered satisfactory for domestic consumption.
prechlorination
The application of chlorine to water or wastewater at or near the treatment plant entrance. Often used in WWTPs following bar screens and grit chambers to control odors in primary settling tanks.
precipitation
(1) The total measurable supply of water received directly from clouds as rain, hail or sleet; usually expressed as depth in a day, month or year and designated as daily, monthly or annual precipitation. (2) The process by which atmospheric moisture is discharged onto a land or water surface. (3) The phenomenon that occurs when a substance in solution is chemically transformed into an insoluble form. (4) The conversion of dissolved solids into suspended solids which may be concentrated subsequently by flocculation and sedimentation. See also "phosphorus removal." (5) The removal of fine particles from an airstream using electrostatically-charged plates.
preliminary treatment
(1) The conditioning of a waste at its source before discharge into a sewer system, to remove or to neutralize substances injurious to sewers and subsequent treatment process or to effect a partial reduction in load on the treatment process. (2) Unit operations at a wastewater treatment plant, such as screening, comminution and grit removal, that prepare the wastewater for subsequent major treatment.
pressure
(1) The total load or force acting on a surface. (2) In hydraulics, unless otherwise stated, usually the pressure per unit area or intensity of pressure above local atmospheric pressure expressed, for example, in pounds per square inch or kilopascals.
pressure filter
(1) An enclosed vessel having a vertical or horizontal cylinder of iron, steel, wood or other material containing granular media through which liquid is forced under pressure. (2) Mechanical filter for partially dewatering sludge.
pressure grouting
The placing of grout (a watery mixture of either Portland cement and water or of various organic chemicals, which hardens in place) under pressure in void spaces in a structure, in soil or rock adjacent to a structure or in and around underground pipes, to strengthen the structure or foundation or make it more watertight.
pressure main
Pressurized sewer lines that deliver wastewater from a pumping station to a treatment plant, a receiving stream or a higher point in the system. Also called force main.
prestressed concrete pipe
A reinforced concrete pipe placed in compression by a highly stressed, closely spaced helical wire winding. The reinforcement permits a concrete pipe to withstand tension forces at the same time it is under compression from surrounding wires.
pretreatment
(1) Any water or wastewater treatment process that precedes primary treatment; may include aeration, equalization, pH adjustment, grit removal, grease removal, screening, skimming, comminution or other processes. (2) The treatment of industrial wastewater at its source before discharge to municipal collection systems.
prime contractor
A contractor who contracts directly with the owner.
primary effluent
The liquid portion of wastewater leaving primary treatment.
primary settling tank
The first settling tank for the removal of settleable and floatable solids through which wastewater is passed in a treatment works.
primary sludge
Sludge obtained from a primary settling tank.
primary treatment
(1) The first major treatment in a wastewater treatment facility, usually sedimentation but not biological oxidation. (2) The removal of a substantial amount of suspended matter but little or no colloidal and dissolved matter. (3) Wastewater treatment processes usually consisting of clarification with or without chemical treatment to accomplish solid-liquid separation. Sometimes called primary wastewater treatment.
prime contract
A construction contract directly between the owner and the contractor for construction. The contractor may have responsibility for a completed unit (a general contractor) or a specific element of a facility (a trade contractor or supplier).
principal gases
The organic or inorganic constituents of landfill gas, greater than one percent by volume, that typically include carbon dioxide, methane, oxygen, and nitrogen.
private sewer
A sewer privately owned and used by one or more properties.
private utility
An enterprise owned by private individuals or by a corporation and operated for the purpose of rendering utility service.
privatization
The private operation and/or private ownership of public service facilities.
probable maximum precipitation (PMP)
The estimated amount of precipitation for a given duration, drainage area, and time of year, which approaches and approximates the maximum that is physically possible within the limits on contemporary hydrometeorological knowledge and techniques. The term describes a precipitation event that has virtually no risk of being exceeded.
process
One or a series of defined steps or operations to accomplish a set purpose.
process water
Water that comes in contact with an end product or with materials incorporated in an end product.
processes to further reduce pathogens (PFRP)
Disinfection processes for biosolids beyond anaerobic digestion, usually with specific time and temperature requirements: including but not limited to composting, thermophilic aerobic digestion, heat treatment, irradiation, and heat drying.
processes to significantly reduce pathogens (PSRP)
Disinfection processes for biosolids, with specific time and temperature requirements: including but not limited to aerobic digestion, anaerobic digestion, and air drying.
procurement
(1) The second construction-related phase of a Clean Water Grant project, occurring between completion of design and the award of a contract for construction, and mainly involving planning and implementation of the bidding. (2) The process used for obtaining goods and services. (3) The advance purchase of supplies and/or equipment.
Professional Land Surveyor
A land surveyor licensed by the State of California pursuant to section 8747 of the Business and Professions Code.
professional services
Services provided by a professional or by an organization that has specific competence in a field of endeavor that requires professional (and technical) knowledge and capabilities and that meets recognized standards of performance.
profile
(1) A vertical section of the surface of the ground, or of underlying strata, or both, along any fixed line. (2) A graphical representation of elevation plotted as a function of distance. (3) In open channel hydraulics, a plot of water surface elevation as a function of channel distance; hydraulic grade line. (4) A longitudinal section along a pipeline, conduit or stream.
program management
Services provided to an owner who has more than one construction project, for the purposes of providing standard technical and management expertise on all projects.
progress payment
Partial payment of the contract amount periodically paid by the owner verifying that portions of the work have been accomplished.
project
The total effort required in all phases from conception through design and construction completion to accomplish the owner's objectives.
project evaluator
Person assigned by the RWQCB to assist the grantee through preconstruction, design, and procurement of a Clean Water Grant project.
project management
The use of integrated systems and procedures by a team of professionals during project design and construction. As applied to a construction project, project management can be used synonymously with construction management.
Proposition 13
The "Jarvis/Gann" initiative approved by California voters in 1978 which added Article XIII A to the State Constitution and drastically limited the use of ad valorem property taxes to fund government activities.
protein
(1) Any of the complex nitrogenous compounds formed in living organisms which consist of amino acids bound together by the peptide linkage. (2) Any of a group of nitrogenous organic compounds of high molecular weight synthesized by plants and animals that, upon hydrolysis, yields amino acids that are required for all life processes.
Protista
The third kingdom, next to the kingdoms of plants and animals, in the classification of living organisms. The Protista include all organisms that do not have any extensive development of tissues, such as algae, fungi, protozoa and bacteria.
protoplasm
Cell material inside the protoplasmic membrane. Protoplasm is composed largely of proteins with significant quantities of fats and carbohydrates and is responsible for all the metabolic activities of the cell.
prototype
The natural or full-scale entity simulated by a model. Also, those structures that are yet to be built and for which model experiments are being conducted.
protozoa
Small one-celled animals including amoebae, ciliates and flagellates.
publicly owned treatment works (POTW)
A wastewater treatment system owned by a public agency such as federal, state, county, city, or a district.
public contact site
Land with a high potential for contact by the public. This includes, but is not limited to, public parks, ball fields, cemeteries, plant nurseries, and golf courses.
public/private partnership
Any arrangement whereby the private sector contractually assumes a public service responsibility that would be traditionally provided by government entities.
Public Records Act
The California law (Government Code 6250 and following) which, with some exceptions, declares all records of public agencies to be open and available to the public.
public sewer
A common sewer controlled by a governmental agency or public utility.
public use of water
The use of water by any agency engaged in the development and distribution of water when such water is offered to all consumers who can be served under their water system and who may apply for this service, up to the full capacity of such system.
public water supply
Either a community or non-community water system which provides piped water to the public for human consumption, if the system has at least five service connections or serves an average of at least 25 individuals daily at least 60 days out of the year. The term includes: (1) collection treatment storage and distribution facilities under control of the supplier, and (2) collection or pretreatment storage facilities not under such control.
public works
Projects undertaken by or for a public agency to construct publicly owned capital improvements.
pump
A mechanical device which increases the total energy of a liquid.
pump characteristic curve
A curve or curves showing the interrelation of speed, dynamic head, capacity, brake horsepower and efficiency of a pump. Sometimes called "pump performance curve."
pump efficiency
The ratio of energy converted into useful work to the energy applied to the pump shaft or the energy difference in the water at the discharge and suction nozzles divided by power input at the pump shaft.
punchlist
A list made near the completion of the construction work indicating items of work that remain unfinished, do not meet quality or quantity requirements as specified or are yet to be performed by the contractor prior to completing the terms of the contract.
purification
The removal of objectionable matter from water by natural or artificial methods.
putrefaction
Biological decomposition, usually of organic matter, with the production of ill-smelling products associated with anaerobic conditions.
putrescibility
(1) The relative tendency of organic matter to undergo decomposition in the absence of oxygen. (2) The susceptibility of wastewaters, effluent or sludge to putrefaction. (3) In water or wastewater analysis, the stability of a polluted water or raw or partially treated wastewater.
putrescibile wastes
Wastes that are capable of being decomposed by micro-organisms with sufficient rapidity as to cause nuisances because of odors, gases, or other offensive conditions.
P-value
The smallest significance level for which the null hypothesis would be rejected, based on the data that was actually observed.
pyrolysis
The destructive distillation of organic compounds in an oxygen-free environment, converting the organic matter into gases, liquids, and char.
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