Decentralized Wastewater Glossary

Physical barrier placed in a component to dissipate energy, direct flow, retain solids and fog, and/or draw water from a specific depth.

Typical feature of a two-compartment septic tank consisting of a wall with a physical opening or pipe configuration used to retain solids in the first compartment.

Non-return valve in which a ball sits within a cylindrical fluid line.

Valve with the closing and opening mechanism formed in the shape of a ball with a hole; rotating the ball orients the hole so that it is either parallel to the flow, allowing unrestricted passage of fluid or perpendicular to the flow, shutting it off.

Total area of an above-grade soil treatment area (mound, modified mound, or areal fill) including the absorption area; perimeter is measured at the interface of imported fill material and original grade; see also absorption area and infiltrative surface; see diagram at absorption area.

Geomorphic component of hills consisting of the concave to linear slope (perpendicular to the contour) which, regardless of the lateral shape is an area that forms an apron or wedge at the bottom of a hillside dominated by colluvial and slope wash processes and sediments (e.g., colluvium and slope alluvium); see also head slope, side slope, nose slope.

Watertight structure or container used to store wastewater for dosing to downstream components or retain effluent for specific treatment processes

Configuration in which flow is controlled so that effluent is neither entering nor leaving the treatment component while a specific operation is being performed; see diagram at sequencing batch reactor.

Reactor in which flow is neither entering nor leaving.

Below-grade soil treatment area consisting of an excavation greater than three feet wide containing distribution media and more than one lateral; typically installed in an excavation 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; see also trench.

1. Process of laying piping, conduit or other structure in a trench shaped to the appropriate contour; 2. Tamping earth around piping, conduit, or other structure to provide support; 3. Material placed under piping, conduit, tank, or other component for uniform structural support.

General term for the rock that underlies the soil and other unconsolidated material or any rock strata that is exposed at the surface.

Device used to trap air in a submerged environment.

Device in a siphon used to introduce air into the siphon bell and stop a dosing event.

Type of shaft or footing excavation, the bottom of which is made larger than the cross section above to form a belled shape.

Soil treatment area designed and installed such that the infiltrative surface and most of the sidewall are below the original ground elevation; a cover of suitable soil stabilizes the final grade, supports vegetative growth and sheds runoff; see also above-grade and at-grade.

1. Soil placed downslope of an excavation to create a level surface on which to work; 2. Shallow excavation adjacent to a deeper excavation (such as for a tank or advanced treatment component) that allows placement of associated piping on undisturbed soil.

Surveying with a level to establish elevations on benchmarks; usually run as part of a cross section, profile, or topographic survey.

Method of protecting workers from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels to reduce the height of vertical cuts and stabilize the excavation.

Method of protecting employees from cave-ins by excavating to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels in accordance with OSHA safety standards for protective systems.

A stationary object of previously determined position and elevation and used as a reference point.

Reference point of known elevation; a permanent bench mark can be established with a brass pin or cap set in concrete, a long metal stake driven in the ground, or a specific point on a concrete bridge or other solid object; a temporary bench mark (needed for only a few days or weeks until a job is completed) could be a wooden stake driven in the ground, or a nail driven in a tree or post; for many temporary bench marks the elevation may be assumed (usually 100.00 feet); permanent bench mark locations should be accurately described in the field book so that a person who had never been to the area could find them.

An absorbent swelling clay consisting mostly of montmorillonite which can either be Na-montmorillonite or Ca-montmorillonite.

1. Natural or constructed raised drainage feature used to divert runoff of stormwater and direct the flow to an effective outlet; may be used in conjunction with a swale; 2. Raised earthen structure designed to contain wastewater such as in a lagoon; see also swale.

Quantity of BOD₅              delivered to a treatment component expressed as mass per time (e.g., pounds of BOD₅  per day).

Amount of oxygen required by bacteria while stabilizing, digesting, or treating wastewater under aerobic conditions; an indirect measure of the amount of organic matter in wastewater; a measure of the relative strength of wastewater expressed in mg/L.

Thin coating of microbial growth, organic matter, and microbial secretions on a solid substrate particle.

Media filter in which the media used is biological in origin (i.e., peat or coir).

Naturally occurring gas that is generated by the breakdown of organic matter by anaerobic bacteria.

Quantity of organic matter delivered to a treatment component expressed mass per time (e.g., pounds per day).

Use of microbiological activity for removal of nitrogen and phosphorus in a wastewater treatment system.

Metabolic activities of bacteria and other microorganisms that convert complex organic materials into simpler, more stable substances.

Treatment methods in which the removal or conversion of constituents is brought about by biological activity; primarily used to remove the biodegradable organic constituents through conversion to cell tissue or gases; also used to remove nutrients (nitrogen and phosphorus).

Total mass of living organisms.

Layer of biological growth and inorganic residue that develops at the infiltrative surface.

Dewatered, primarily nutrient-rich organic material generated as a by-product of biological wastewater treatment processes that can be recycled (such as for use as a soil amendment); see also residuals and septage.

Soil or fill material which removes pollutants from treated effluent by processes which include physical filtration of bacteria and other constituents, adsorption of viruses and bacteria by clay and organic matter, biological destruction of pathogens by soil microorganisms, sorption or precipitation of phosphorus, biochemical transformations of organic and nitrogen compounds, and biological assimilation of phosphorus and nitrogen.

Portion of the wastewater stream that originates from toilet fixtures, dishwashers, and food preparation sinks; see also graywater.

To drain a liquid or gas, as in bleeding accumulated air from a water line or bleeding (draining) a trap of accumulated water.

Device constructed of resilient material (such as concrete) and placed beneath a pump in order to raise the pump intake elevation.

Soil structure descriptor for soil aggregates with blocklike shapes; includes angular blocky (exhibiting sharp, well-defined edges) and subangular blocky (exhibiting more rounded edges).

See five-day biochemical oxygen demand.

Flexible device attached to piping to provide a watertight seal.

Configuration in which a short manifold is located at the lower elevation of a soil treatment area.

Media filter that does not incorporate a liner or other physical barrier between the media and the existing soil on which it has been placed; used as a final treatment and dispersal component.

Service line piping that collects and conveys wastewater from the source to further collection and storage, treatment and dispersal components; includes access for maintenance such as cleanouts.                           

Condition wherein sludge solids do not separate from the liquid under quiescent conditions; under aerobic conditions may be associated with the growth of filamentous organisms, low dissolved oxygen (DO), or high sludge loading rates; under anaerobic conditions, may be associated with attachment of gas bubbles to solids.

See switching valve.

Distribution media consisting of two or more conjoined perforated pipes.

Tendency of a body to float in water or other liquid; upward force that a fluid exerts on an object that is less dense than itself.

See recirculating splitter valve.

Depth from the surface of the finished grade to the top of a component.

Attraction (cohesion of liquid molecules and adhesion between a liquid and a solid surface) resulting in movement of liquid from a zone of greater liquid content to an area of lesser liquid content.

Attraction (adhesion) of liquid to a solid surface.        

A zone in the soil just above the plane of zero water pressure (water table) that remains saturated or almost saturated with water due to capillary action that draws water upward.                                

Quantitative measure of the amount of oxygen consumed by bacteria while stabilizing, digesting, or treating the organic matter under aerobic conditions over a five-day incubation period while in the presence of a chemical inhibitor to block nitrification; cBOD is expressed in milligrams per liter (mg/L); see also nitrogenous biochemical oxygen demand; and nitrification.

Enclosed space (tank) mounted on a truck, trailer, or skid which is intended to receive and contain material for transport from the source facility to the receiving facility.

One or more partitions installed across the shortest dimension of a cargo tank that partially restrict the free flow of liquid from end to end in the tank; designed to reduce liquid surge and increase vehicle handling safety.

An electrical system for prevention of rust, corrosion, and pitting of steel and iron surfaces in contact with Water, wastewater or soil. A low-voltage current is made to flow through a liquid (water) or a soil in contact with the metal in such a manner that the external electromotive force renders the metal structure cathodic. This concentrates corrosion on auxiliary anodic parts which are deliberately allowed to corrode instead of letting the structure corrode.                                                                           

Separation of a mass of soil or rock material from the side of an excavation, or the loss of soil from under a trench shield or support system, and its sudden movement into the excavation, either by falling or sliding, in sufficient quantity so that it could entrap, bury, or otherwise injure and immobilize a person.

The formation and collapse of a gas pocket or bubble on the blade of an impeller or the gate of a valve; the collapse of this gas pocket or bubble drives water into the impeller or gate with a terrific force that can cause pitting on the impeller or gate surface; accompanied by loud noises that sound like someone is pounding on the impeller or gate with a hammer.                                                                    

Configuration in which a long manifold is installed perpendicular to two sets of distribution laterals that extend in opposite directions along the contour; the supply line may connect to the manifold in the center or at one end; used on level or nearly-level sites.

Pump consisting of a rotating vane(s) [impeller(s)] enclosed in a housing (volute); the impeller draws liquid in and discharges it from the pump under pressure.

Documentation of the proper construction of the system.

Program to substantiate the capabilities of personnel by documentation of experience and learning in a defined area of endeavor.

See cesspool.

Underground pit into which raw household wastewater is discharged and from which the liquid seeps into the surrounding soil; may or may not be partially lined; if septic tank effluent is discharged to such a component, it is considered a seepage pit; emphasis is on disposal rather than treatment, resulting in this technology being phased out.

See trencher.

1. An enclosed structure or container used for treatment or storage of effluent in an onsite wastewater treatment system; may be free-standing or integral with another structure 2. Pre-formed, manufactured distribution media with an open-bottom configuration; used in soil treatment areas.

Valve that allows flow in only one direction by closing when the flow direction reverses.

Amount of the organic matter in wastewater that can be oxidized by a very strong chemical oxidant; typically measured by a standard test using dichromic acid as the oxidant.

Waterless toilet with a tank that contains a chemical to limit decomposition of non-water-carried human waste during storage prior to offsite treatment.

Process involving the addition of chemicals to obtain a desired result, such as precipitation, coagulation, flocculation, pH adjustment, disinfection, or sludge conditioning.

Treatment methods in which the removal or conversion of constituents is brought about through the addition of chemicals or by other chemical reactions; includes precipitation, adsorption and disinfection.

1. Shank tillage implement that disrupts the soil to loosen and roughen the surface 2. Static plow shank used to slice the soil during installation of subsurface drip tubing.

chemical compound present because of the chlorine disinfection process when the effluent contains ammonia; chloramines are relatively persistent in the environment and toxic to fish and amphibians.

see disinfection, chlorine.

component that delivers chlorine (liquid, tablet, or gas) as an agent for disinfection.

term commonly used to describe a chlorine source such as sodium hypochlorite, a highly reactive chemical used as a disinfectant and oxidizing agent.

process used to inactivate microorganisms by the addition of chlorine (such as in the form of sodium hypochlorite); see also chlorinator and chlorine.

total amount of chlorine (free and combined available forms) remaining in effluent at the end of a specified contact period after the chlorination process.

relative purity, strength, or saturation of a color; directly related to the dominance of the determining wavelength of the light and inversely related to grayness; one of the three variables of color; see also Munsell Color System; hue; and value.

A protective device that automatically interrupts electrical flow when excessive current is detected, preventing damage to itself or wiring or creating hazardous conditions

Total volume of effluent dosed to the treatment unit relative to the volume of forward flow to the next component of the treatment train; calculated by dividing the total dosed volume by the forward flow volume (total dosed volume / forward flow volume); see also recirculation ratio and forward flow.

Process or combination of processes that uses separation (settling and flotation) to remove suspended solids from wastewater.

Component or tank that uses separation to remove suspended solids from wastewater.

1. Soil separate consisting of particles <0.002 mm in equivalent diameter; 2. in reference to clay mineralogy, a naturally occurring material composed primarily of fine-grained minerals, which is generally plastic at appropriate water content and will harden when dried or fired; see also soil separate, soil textural class and soil texture.

device designed to provide access for removal of deposited or accumulated materials, generally from a pipe.

See clear water.

Fraction of the wastewater stream including, but not limited to surface water, groundwater, condensate, ice machine drainage, and/or discharge from swimming pools, hot tubs, and water treatment devices; see also wastewater.

Volume or zone within a component that contains clarified wastewater; for example, after wastewater has had sufficient detention time in a septic tank, the clear zone lies between the scum and sludge layers.

See biomat.

See cluster wastewater treatment system.

Wastewater treatment systems designed to serve two or more sewage-generating dwellings or facilities with multiple owners; typically includes a comprehensive, sequential land-use planning component and private ownership.

Process by which colloidal particles come together irreversibly to form larger masses.

Bubble of 3 to 8 mm diameter generated by an air diffuser.