Decentralized Wastewater Glossary

measure of all suspended solids in a liquid, typically expressed in mg/L; to measure, a well-mixed sample is filtered through a standard glass fiber filter and the residue retained on the filter is dried to a constant weight at 217 to 221 degrees F (103 to 105 degrees C); the increase in the weight of the filter represents the amount of total suspended solids.

sudden introduction of a substance or substances that impair or destroy biological activity within a wastewater treatment process.

organic compounds originating from residential and non-residential sources, such as ingredients in drugs, pesticides, consumer products, and industrial process agents (usually present in concentrations much lower than one mg/L) which may have adverse ecological and/or human health effects; see also pharmaceutical and personal care products.

propulsion method using tracks, typically resulting in lesser ground pressure due to broader soil contact area; see also wheeled.

mechanical device that converts air or water pressure to a proportional electrical current.

local bench mark established from a referenced bench mark.

process by which plants release water vapor to the air.

optional first component of a wastewater treatment system, often used with a proprietary aerobic treatment unit (ATU), typically having a limited detention time, and used to remove larger items or inorganic material in the wastewater stream; trash tanks provide limited anaerobic treatment.

method, technique, or process designed to remove solids and/or pollutants from wastewater prior to conveyance to a final treatment and dispersal component or reuse; often, this treatment is designed to meet a primary, secondary, tertiary, and/or disinfection treatment standard; includes pretreatment and advanced treatment.

non- or slowly-degradable media used for physical, chemical, and/or biological treatment in a wastewater treatment component.

site-specific combination of components in a specified order that constitute a wastewater treatment system; a simple example of a treatment train is a septic tank and a soil treatment area.

1. soil treatment area (STA) configuration consisting of an excavation with a width of 3 feet or less containing distribution media and one lateral; 2. below-grade soil treatment area consisting of one or more trenches installed in an excavation such that the bottom of the infiltrative surface is typically 18 to 36 inches below original ground elevation; utilizes pressure or gravity distribution; a cover of suitable soil stabilizes the final grade, supports vegetative growth and sheds runoff; 3. excavation in the soil for drainage diversion; 4. excavation for placement of piping, electrical wire or conduit; see also trench excavation.

narrow excavation (in relation to its length) made below the surface of the ground; in general, the depth is greater than the width, but the width of a trench (measured at the bottom) is not greater than 15 feet (4.6 m). if forms or other structures are installed or constructed in an excavation so as to reduce the dimension measured from the forms or structure to the side of the excavation to 15 feet (4.6 m) or less (measured at the bottom of the excavation), the excavation is also considered to be a trench.

see shield.

see shield.

machine that uses a chain with attached cutters to open a trench by cutting, removing, and depositing spoil to the side of the trench or onto a discharge conveyor.

type of media filter which uses a variety of media such as rigid plastics of varying shapes, stone, or tire chips; includes a clarifier in its configuration and may include a recirculation mode.

act of identifying and correcting the root causes of system malfunction.

relative clarity of effluent due to the presence of varying amounts of suspended organic and inorganic materials or color.

centrifugal pump with a curved volute that causes liquid to discharge along the centerline of the impeller;                 see also  multi-stage pump.

temporary point on which rod readings are taken to move the leveling instrument along a survey path; a foresight (FS or +) is taken on the turning point to obtain its elevation (initially, elevation of turning point is unknown); the instrument is then moved from its position and set up at a new position beyond the turning point; a backsight (BS or +) is then taken on the turning point to determine the height of the instrument (HI); the turning point must be a firm object, such as a stone, stake, pipe, fence post, or axe head so that the elevation will not change while the instrument is being moved; if the turning point is altered while the instrument is being moved, the survey must go back to the last permanent point of known elevation (i.e., a bench mark).

a liquid level sensing arrangement in a simplex pumping system using two single differential float switches: one for pump operation (both activation and deactivation) and a second for high water alarm activation.

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose-directed water); that provides an increased level of protection against corrosion; and that will be undamaged by the external formation of ice on the enclosure.                                                                                               

OSHA soil classification that includes cohesive soils with an unconfined compressive strength of 1.5 ton per square foot (TSF) (144 kPa) or greater; examples of cohesive soils are: clay, silty clay, sandy clay, clay loam and, in some cases, silty clay loam and sandy clay loam; cemented soils such as caliche and hardpan are also considered Type A; however, no soil is Type A if: (i) the soil is fissured; or (ii) the soil is subject to vibration from heavy traffic, pile driving, or similar effects; or (iii) the soil has been previously disturbed; or (iv) the soil is part of a sloped, layered system where the layers dip into the excavation on a slope of four horizontal to one vertical (4H:1V) or greater; or (v) the material is subject to other factors that would require it to be classified as a less stable material.

OSHA soil classification that includes cohesive soil with (i) an unconfined compressive strength greater than 0.5 TSF (48 kPa) but less than 1.5 TSF (144 kPa); or (ii) granular cohesionless soils including: angular gravel (similar to crushed rock), silt, silt loam, sandy loam and, in some cases, silty clay loam and sandy clay loam. (iii) previously disturbed soils except those which would otherwise be classed as Type C soil. (iv) soil that meets the unconfined compressive strength or cementation requirements for Type A, but is fissured or subject to vibration; or (v) dry rock that is not stable; or (vi) material that is part of a sloped, layered system where the layers dip into the excavation on a slope less steep than four horizontal to one vertical (4H:1V), but only if the material would otherwise be classified as Type B.

OSHA soil classification that includes cohesive soil with (i) an unconfined compressive strength of 0.5 TSF (48 kPa) or less; or (ii) granular soils including gravel, sand, and loamy sand; or (iii) submerged soil or soil from which water is freely seeping; or (iv) Submerged rock that is not stable, or (v) material in a sloped, layered system where the layers dip into the excavation or a slope of four horizontal to one vertical (4H:1V) or steeper.

US Coast Guard approved Marine Sanitation Device that is designed to simply hold waste material for pump-out into a shore-based facility, also known as a holding tank which performs no treatment; see also holding tank.

oxygen required to complete the oxidation, synthesis, and endogenous respiration in a sample of wastewater; see also five day biochemical oxygen demand.

device that measures depth to liquid level by transmitting and receiving sound waves.

light waves beyond the visible spectrum; used for disinfection of water and wastewater; see also disinfection

physical process used to inactivate microorganisms by irradiating them with ultraviolet light (254-nm germicidal wavelength) to disrupt their metabolic activity, thus rendering them incapable of reproduction; see also ultraviolet.

condition in which a component or system is not operating as intended, indicating a need to implement maintenance, upgrades, repairs, or further investigation; see also acceptable and malfunction.

load per unit area at which a soil will fail in compression; determined by laboratory testing, field estimation using a pocket penetrometer, thumb penetration tests, and other methods.

perforated pipe located below the media of a media filter; designed to collect treated effluent.

concept of distributing effluent evenly over the surface of a component over both time and space.

description or specification of particle size distribution calculated by dividing the diameter of particle (millimeters) of which 60% by weight is smaller, by the diameter of particle (millimeters) of which 10% by weight is smaller; expressed mathematically as D60/D10; see also particle size distribution.

dispersal component with an unlined bed using evaporation, transpiration, and adsorption for dispersal of effluent with an unlined bed; sometimes called an evapotranspiration/infiltration (ETI) bed.

movement of water in a porous soil or media that is not filled to capacity with water; the water flow is along the surface of the particles, allowing air and gases to move through the interior of the larger pore space.

soil in which the pore spaces contain water at less than atmospheric pressure; typically, smaller pore spaces contain water because of tension and larger pore spaces contain air and other gases.

see anaerobic upflow filter.

improving a system by adding a device or component (or replacing a given device or component with one of higher quality) to increase the system’s effectiveness or facilitate operation and maintenance.

vertical members of a trench shoring system placed in contact with the earth and usually positioned so that individual members do not contact each other. uprights placed so that individual members are closely spaced, in contact with or interconnected to each other, are often called "sheeting."

aqueous fluid containing urea and other materials generally exiting via the human urogenital pathway.

toilet fixture designed to separate urine from other waste materials.

device used to facilitate air entry during depressurization; also called an air/vacuum release valve; see also air/vacuum release valve.

valve that serves as a type of backflow-prevention device that prevents cross-contamination by reverse flow; see also air/vacuum release valve.

measurement of the suction produced in a vacuum system relative to ambient atmospheric pressure.

pump that removes air from a cargo tank to create a vacuum (or partial vacuum); may also be operated in reverse mode to produce pressure.

process of allowing air entry into a component to relieve a vacuum condition.

valve that limits the vacuum level in a vacuum cargo tank (or suction line) to a preset level by allowing air to enter, thereby assuring that the operating vacuum level is not exceeded.

motorized vehicle equipped with a vacuum system consisting of vacuum pump, cargo tank and associated equipment.

aerated, unsaturated region of soil above the zone of saturation.

one of the three variables of color, described as the degree of lightness or darkness of the color in relation to a neutral gray scale; on a neutral gray scale, value extends from pure black to pure white; see also Munsell Color System; hue; and chroma.

mechanical device used to close off, regulate, or divert the flow of fluid.

housing that encloses an operating component or device and extends to the ground surface, allowing access for component inspection, operation, etc.

controlling or modulating flow through a system by manually or automatically opening or closing a valve to various degrees; in a pump system, changing the valve to various positions between full open and full closed regulates the amount of flow delivered and the operating pressure or head.

waterless toilet mounted on a vented holding tank designed to store non-water-carried human waste prior to offsite treatment.

device that allows the active or passive entrance or exit of gases from a component.

vertical distance between the infiltrative surface and a limiting condition, such as highest groundwater level, bedrock, etc.

trench installed with 4 or more feet of distribution media below the lateral.

mechanical device such as a jumping jack that consolidates loose soil material.

oscillating plow shank used for installing subsurface drip tubing and utility lines.

an obligate parasite dependent on a host cell for its metabolic and reproductive needs; a constituent of concern in biological wastewater treatment systems.

capable of evaporating at relatively low temperatures.

class of organic compounds that readily evaporates; includes liquids and solids at natural environmental temperature; examples include solvents, adhesives and fuels).

weight loss on ignition of total solids, not distinguishing between inorganic and organic matter, and including loss due to decomposition or volatilization of some mineral salts at 1,022 degrees F (550 degrees C).

the electric potential difference between two points, which causes the movement of electric charge.

1. the amount of space that a liquid or solid object occupies, typically measured in cubic units; 2. the space occupied within the boundaries of an object (such as a tank, chamber or compartment) in three-dimensional space; typically measured in cubic units; also known as the capacity of the object.

of or pertaining to measurement by volume.

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

centrifugal pump using a recessed impeller designed to create a whirlpool within the pump casing to convey solids with minimal contact.

horizontal members of a shoring system placed parallel to the excavation face whose sides bear against the vertical members of the shoring system or earth.

clean graded media of specified size range, offering a minimum specified void space, having a hardness value of three or greater on the Moh’s scale of hardness (can scratch a copper penny), prepared to be relatively free of fine materials that might otherwise impair absorption area performance; placed on the infiltrative surface.

clear water, stormwater, industrial, sewage (domestic or commercial), or any combination thereof, carried by water.

treatment or processing of wastewater to produce water of a quality appropriate for another use, including recycling or reuse; see also wastewater recycling and wastewater reuse.

reclamation process of collection and treatment of wastewater on-site for return and use back into the same site; for example, collection and reclamation of graywater from an establishment for subsequent toilet flushing in that same establishment; see also wastewater reuse.

reclamation process of collection and treatment of wastewater for the deliberate application of that treated wastewater for a beneficial purpose such as turf irrigation; see also wastewater recycling.

constructed basin lined with either soil with very low permeability or a synthetic material, surrounded with berms and which contains at least three feet of wastewater which utilizes sunlight, wind or mechanical aeration, and natural bacteria to break down waste via physical, chemical and biological processes to stabilize wastewater; typically consists of two or more basins with operational controls allowing or facilitating flow through the basins.

assembly of components for collection, treatment and dispersal of sewage or effluent.

process of removing biomass from activated sludge in the pretreatment process.

management of water resources to eliminate waste or maximize efficiency utilizing such methods as using the same water again before it becomes wastewater, installing water-efficient plumbing, or wastewater recycling and reuse.

method of settling backfill using water.

specific, measurable, and enforceable standard that establishes limits and measurement frequency for pollutant concentrations or mass loads in treated wastewater discharged to groundwater or surface water.