Decentralized Wastewater Glossary

Effluent from a septic tank or other treatment device with a BOD⁵                           less than or equal to 170 mg/L; TSS less than or equal to 60 mg/L; and fats, oils, and grease less than or equal to 25 mg/L.

Solids generated and retained in wastewater treatment components during the treatment of sewage, including sludge, scum, and pumpings from grease interceptors, septic tanks, aerobic treatment units, or other components;                             see also  biosolids and septage.

Ability to recover from or adjust easily to adversity or change; ability to recover from adverse conditions (excessive organic, hydraulic or nutrient loading or microbial inhibitors) or to adjust processes in response to changing waste streams.

Capable of rebounding or adjusting to "shocks" to the system by way of a robust design and vigilant construction practices.                       

1. Person or organization that administers and conducts a comprehensive set of activities recognized by the regulatory authority; 2. Legal entity that has the managerial, financial, and technical capacity to ensure the long-term, cost-effective operation, maintenance and monitoring of onsite and/or cluster wastewater treatment systems in accordance with applicable regulations and performance requirements (e.g., a wastewater utility or wastewater management district).

Horizon or condition in the soil profile or underlying strata that restricts movement of fluids; a restrictive layer may constitute a limiting soil/site condition; examples include fragipan, spodic horizons, massive structural grade, or certain bedrock, etc.; see also limiting condition.

See detention time.

Volume of solids-laden effluent returned to a preceding component of a treatment train; see also return flow.

1. Volume of effluent returned to a previous component of a treatment train configured with a recirculation mode; 2. Volume of effluent used to backflush or forward flush a component; 3. Volume of solids-laden effluent returned to a preceding component of a treatment train; also known as return activated sludge.                                                   

1. Portion of the distribution system through which effluent is routed back to a preceding component such as in a drip distribution system; 2. Portion of a treatment component that conveys effluent back to an upstream component such as an activated sludge return or a recirculating media filter.

Manifold that allows effluent from two or more laterals to be collected and conveyed to a return line.

See water reuse.

Filtration method that removes ions and molecules from a solution by applying pressure to a semipermeable membrane.                  

Slope or gradient; inclination of a line with respect to the coordinate axes; the rise along the y-axis divided by the run along th x-axis.

1. Vertical piping that begins at the lateral and terminates in a spray distribution head in a spray dispersal system; 2. In reference to tanks, see access riser.

Piping connected to the loading pipe valve and projecting into a cargo tank that facilitates distribution of material within the tank during loading.

Naturally occurring inorganic material with a defined structure and mineralogical composition.

Unattached pieces of rock 2 mm in diameter or larger.

Reading taken on a leveling rod when sighting through the telescope of an optical leveling instrument.

A device used to measure the flow rate of gases and liquids. The gas or liquid being measured flows vertically up a tapered, calibrated tube. Inside the tube is a small ball or bullet-shaped float (it may rotate) that rises or falls depending on the flow rate . The flow rate may be read on a scale behind or on the tube by looking at the middle of the ball or at the widest part or top of the float.                                                                                

Laser level providing a plane of reference over open areas.

Type of attached growth pretreatment component consisting of disks mounted on a drive shaft which rotates; microorganisms attached to the discs are alternately exposed to free oxygen in the atmosphere and the wastewater.

See recirculating splitter valve.

Length of drip tubing placed on a single contour of a drip distribution lateral.

Precipitation, snow melt, or irrigation in excess of what can infiltrate the soil surface in a given area and thus, flows across the surface.

Amount of precipitation (and/or irrigation) minus surface storage, infiltration, evapotranspiration, and interception, that exits a defined area.

Surface water that enters an area from upslope.

Part or device at a particular location in a component that allows a sample to be collected for analysis.

Soil particle between 0.05 and 2.0 millimeters in diameter; see also soil separate; soil textural class; and soil texture.

Media filter which uses sand meeting specific criteria as the treatment media.

Below grade bed installed after native soil is excavated and replaced with approved soil material; configurations and terminology vary among jurisdictions.

Below-grade trench installed after native soil is excavated and replaced with approved soil material; configurations and terminology vary among jurisdictions.

Pipe fitting in the shape of a “T” with a long-sweep radius; commonly used as a part of an inlet or outlet baffle in a septic tank.

Condition wherein all available soil pore space is occupied by water.

A measure of how easily water moves through soil or rock when all the pore spaces are completely filled with water.

Soil in which the voids are filled with water; saturation does not require flow; saturation, or near saturation, is necessary for the proper use of instruments such as a pocket penetrometer or sheer vane.

Supervisory control and data acquisition

1. Proportion between two sets of dimensions, as between those of a drawing and its original; for example, the scale of a drawing may be expressed as 1/4 inch = one foot; 2. Measuring tool used by architects and engineers in preparing drawings to a proportionate scale; 3. To measure a drawing with a scale. 4. Either pan or tray of a balance; 5. To climb, as a ladder; 6. Series of graduated marked spaces for measuring something, as on a thermometer; 7. Rust occurring in thin layers; 8. hard deposit of minerals on heater coils and pool surfaces.

Process of abrading or scratching the infiltrative surface prior to installation of a final treatment and dispersal component.

1. Porous material or mesh configured as a plate or cylinder that allows the passage of particles smaller than specified size, (e.g., an effluent screen) according to a specific flow/pressure relationship; a screen has area but no depth with respect to flow; 2. use of a porous material or mesh to separate particles by size; see also filter.

Filter consisting of a mesh material configured as a cylinder and used to remove particles larger than a specific size in pressurized systems.

Layer of floating material on a liquid surface.

Physical barrier installed in an access riser, manhole or lift station; serves as a safety feature to restrict unauthorized entry when the primary cover is removed.                                    

Second of two automatic shut-off valves that prevent a cargo tank from being overfilled and possibly causing ejection of material from the tank through the pump.

Biological and chemical treatment processes designed to remove organic matter; a typical standard for secondary effluent is BOD and TSS less than or equal to 30 mg/L each on a 30-day average basis.

Settling of solid material out of a liquid, typically accomplished by reducing the velocity of the liquid below the point at which it can transport the suspended material; may be enhanced by coagulation and flocculation; also known as settling.

See bed.

Excavation deeper than it is wide, which receives septic tank effluent and from which the effluent seeps into the surrounding soil through the bottom and openings in the side of the pit; emphasis is on disposal rather than treatment, resulting in this technology being phased out; see also cesspool.

Unconsolidated material that meets specific textural criteria and is used as part of a dispersal component; see also fill.

Optical level with a prismatic device suspended on fine, nonmagnetic wires, such that when it is approximately centered the force of gravity on the prismatic device causes the optical system to swing into a position so that the line of sight is horizontal.

Pump that is designed such that a small amount of liquid retained in the housing enables the pump to initiate operation without additional liquid.

Part or device that detects a chemical, physical, or mechanical signal and converts it into an electronic one.

Minimum vertical or horizontal space required between specified components, between components and physical features, or between components and legally-defined boundaries.

Liquid and residuals removed from a septic tank or other pretreatment device, seepage pit, cesspool, portable toilet, Type III marine sanitation device, or similar domestic wastewater treatment works that receives only domestic wastewater; see also biosolids and residuals.

See onsite wastewater treatment system (OWTS).

Water-tight, covered receptacle for treatment of sewage; receives the discharge of sewage from a building, separates settleable and floating solids from the liquid, digests organic matter by anaerobic bacterial action, stores digested solids through a period of detention, allows clarified liquids to discharge for additional treatment and final dispersal, and attenuates flows.

Partially treated sewage that is discharged from a septic tank.

Collection system that uses septic tanks to separate solids and allow gravity flow of effluent to a subsequent component.

Collection system that uses a septic tank to separate solids and incorporates a pump vault, pump and associated devices to convey effluent under pressure to a subsequent component.

Component in which batch type suspended growth (activated sludge) processes are carried out in the same tank in stepwise order (e.g. fill, treat, settle, decant, and draw).

Valve used to automatically direct flow to two or more final treatment and dispersal components, one or more at a time, and in a prescribed order.

Distribution method in which effluent is loaded into one trench and fills it to a predetermined level before passing through a relief line or device to the succeeding trench; the effluent does not pass through the distribution media before it enters succeeding trenches; see also serial distribution.

Distribution method in which effluent is loaded into one trench and fills it to a predetermined level before passing through a relief line or device to the succeeding trench; effluent passes through the distribution media before entering succeeding trenches in a single uninterrupted flow path; see also sequential distribution.

Performing one or more activities related to wastewater treatment systems, including installation, inspection, operation, maintenance, assessment, and mitigation.

The total time a device, component or system performs its intended function.

Any person who performs work in relation to wastewater treatment systems; may include site evaluators, designers, inspectors, installers, O&M service providers, and pumpers.

Minimum horizontal separation distance between system components and site/facility features; typically defined by code or regulation.

Third step in the sequential treatment processes that occur in a sequencing batch reactor (SBR).

Measure of suspended solids that will settle out of suspension within a specified period of time; typically expressed as milliliters per liter (mL/L).

Process of subsidence and deposition of suspended matter carried by a liquid; typically accomplished by reducing the velocity of the liquid below the point at which it can transport the suspended material; see also sedimentation.

Time during which suspended, aggregated, precipitated, or colloidal substances settle by gravity.

Untreated wastes consisting of blackwater and graywater from toilets, food preparation areas, baths, sinks, lavatories, laundries, and other plumbing fixtures in places of human habitation, employment, or recreation.

System of piping, lift stations, and other appurtenances forming a network of service lines, laterals and collection lines to receive and convey wastewater either by gravity or pressure; typical maintenace access includes cleanouts and manholes located in the piping network; includes alternative collection appurtenances such as septic tank effluent gravity (STEG), septic tank effluent pump (STEP), vacuum sewer, and grinder or ejector pump basin systems.

Appurtenance in a sewage collection system consisting of a tank or basin for collecting wastewater and a pump with associated controls to convey the wastewater to downstream components.

See sewage collection system.

Bed installed in an excavation less than 18 inches deep such that the entire infiltrative surface is below the original ground elevation.

Final treatment and dispersal component in which highly-treated effluent is distributed into trenches installed in the upper portion (8 to 12 inches) of the soil profile and dosed via low-pressure distribution laterals.

Trench installed in an excavation typically greater than 6 but less than 18 inches deep such that most of the entire infiltrative surface is below the original ground elevation; the orifices in the distribution piping are at or below original ground elevation.

Members of a shoring system that retain the earth in position and in turn are supported by other members of the shoring system.

Structure that is able to withstand the forces imposed on it by a cave-in and thereby protect employees within the structure; can be permanent structures or can be designed to be portable and moved along as work progresses; additionally, shields can be either pre-manufactured or job-built in accordance with OSHA 1926.652(c)(3) or (c)(4). Shields used in trenches are usually referred to as "trench boxes" or "trench shields."

Structure such as a metal hydraulic, mechanical or timber shoring system that supports the sides of an excavation and which is designed to prevent cave-ins.

The hillslope-profile position that forms the convex, erosional uppermost inclined surface near the top of a slope. If present, it comprises the transition zone from summit to backslope. Compare summit, crest, backslope, footslope, and toeslope (Schoeneberger and Wysocki, personal communication, 2013; Hawley and Parsons, 1980).

See expansive clay mineralogy.

Valve that prevents flow from entering a component.

Configuration in which a long manifold is installed perpendicular to one set of distribution laterals that extend in one direction 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.

A geomorphic component of hills consisting of a laterally planar area of a hillside, resulting in predominantly parallel overland water flow (e.g., sheet wash); contour lines generally form straight lines. Side slopes are dominated by colluvium and slope wash sediments. Slope complexity (downslope shape) can range from simple to complex (Schoeneberger and Wysocki, personal communication, 2013). Compare base slope, head slope, nose slope.

See faces.

Use of specific size sieves to determine the gradation (the distribution of aggregate particles, by size, within a given sample) in order to determine compliance with design, production control requirements, and verification specifications.

Mineral particles that range in diameter from 0.02-0.002 mm in the International System or 0.05-0.002 mm in the USDA-NRCS system; see also soil separate, soil textural class and soil texture.

Control that operates a single device (e.g., a simplex pump system).

Laser level projecting a string line that can be seen on a target regardless of lighting conditions.

Float switch that performs both the energizing and deenergizing operations.

Soil structure descriptor for soil consisting of non-coherent individual particles (e.g., loose sand).

Flow configuration wherein effluent moves through a coir media filter only once.

Flow configuration wherein effluent moves through a media filter only once.

Flow configuration wherein effluent moves through a peat media filter only once.

Flow configuration wherein effluent moves through a sand media filter only once.

Device used for demand dosing effluent from a tank at a given elevation to a component at a lower elevation, accomplished by means of suction created by the weight of the liquid in the conveying pipe.

Dosing tank or compartment which provides storage of effluent and contains a siphon to convey effluent from the tank to another pretreatment process or to a final treatment and dispersal component.