Decentralized Wastewater Glossary

Increasing the capacity of a wastewater treatment system.

Soil in which the clay fraction is dominated by expansive 2:1 clay minerals such as smectite or vermiculite.

Soil that undergoes significant volume change upon wetting and drying, usually because of a high content of expansive clay minerals; see also expansive clay mineralogy.

Wastewater treatment process that uses activated sludge to biologically convert non-settleable (suspended, dissolved, and colloidal) organic materials to a settleable product using aerobic and facultative microorganisms; typically followed by clarification and sludge return.

Alteration of a wastewater treatment system resulting in an increase in capacity, lengthening, or expansion of the existing collection, treatment or dispersal component.

Vertical or inclined earth surfaces formed as a result of excavation work; also known as sides.

Bacteria that can metabolize with or without molecular oxygen present in the environment.

1. Term commonly used in regulation to describe a system malfunction; see also malfunction; 2. Breakage, displacement, or permanent deformation of a structural member or connection to reduce its structural integrity and its supportive capabilities.

Indicator bacteria common to the digestive systems of warm-blooded animals that is cultured in standard tests to indicate either contamination from sewage or the effectiveness of disinfection processes; generally measured as number of colonies/100 mL or most probably number (MPN); see also most probable number.

Parameter that describes the orientation of the manifold relative to the supply line and/or laterals in a system.

Amount of water in a soil after drainage due to gravity following a thorough wetting event.

Act of opening a cleanout or valve to allow the movement of effluent to scour accumulated materials out of a pipe or pipes.

See operating pressure.

1. Unconsolidated material that meets specific textural criteria and is used as part of a dispersal component; 2. Unconsolidated material used to change grade or to enhance surface water diversion; 3. Any other human-transported unconsolidated soil material; see also cut and fill. 4. fFrst step in the sequential treatment processes that occur in a sequencing batch reactor or SBR.

See elevated system.

Device that removes constituents through processes such as sieving, stagnation, adsorption, or absorption; a filter has both area and depth with respect to flow; see also screen.

Media used to construct a filter for treatment of effluent; ideal filter sand has a relatively greater effective size (D10 value) and a low uniformity coefficent (UC); a jar test performed on the site verifies the acceptable amount of fines present in media; see also effective size, uniformity coefficient, and jar test.

Removal of suspended materials using processes such as sieving, stagnation, adsorption, absorption, and possibly biochemical degradation.

Portion of an excavation extending from above the initial backfill to final grade; see diagram at bedding.

Soil with characteristics suitable for stabilizing the surface of system components, supporting vegetative growth and (in some cases) facilitating gas exchange.

Treatment system consisting of one or more components that provide for effluent distribution and final removal of constituents from effluent prior to dispersal back into the receiving environment via a soil treatment area.

Bubble of 0.2 to 3 mm diameter generated by an air diffuser.

Diffused aeration device that disperses very small air bubbles into mixed liquor in an aerobic treatment unit aerobic process; often described in relative sizes (e.g., micro-, fine, etc.).

Final earth grade required by specifications.

Description of a soil material that tends to break along definite planes of fracture with little resistance, or a material that exhibits open cracks, such as tension cracks, in an exposed surface.

Quantitative measure of the amount of oxygen consumed by bacteria while stabilizing, digesting, or treating biodegradable organic matter under aerobic conditions over a five-day incubation period; expressed in milligrams per liter (mg/L).

Residue of total, suspended, or dissolved solids (mineral fraction) after heating to dryness for a specified time at a specified temperature.

Configuration wherein the microorganisms responsible for treatment colonize a fixed medium; see also suspended growth process.

Relative estimate of discharge into a system by various types of plumbing fixtures; used in the determination of design flow.

Piping used to connect spray distribution heads to laterals using flexible pipe as a riser; allows proper placement of the distribution head in a location that may be both vertically and horizontally remote from the lateral; helps protect and isolate the lateral from damage.

Sensor installed in a pump vault or tank which opens or closes an electrical circuit in response to changing liquid levels, thereby controlling equipment operation.

Removable device located within a pump vault or dosing tank to which float sensors are attached.

Material in wastewater with a density less than that of water.

Collection of smaller particles agglomerated into larger particles as a result of chemical, physical, or biological treatment; the larger particles can be more readily settled or filtered out of the effluent; see flocculation.

Water-soluble organic polyelectrolytes that are used alone or in conjunction with inorganic coagulants to agglomerate the solids present in water; this process forms large, dense floc particles that settle rapidly.

Agglomeration of colloids and finely divided suspended matter by biological, chemical, hydraulic and/or mechanical means.

Any area susceptible to inundation by flood waters from any source and subject to the statistical 100-year flood; such an area has a one percent chance of flooding each year.

Channel of a watercourse and the adjacent land areas (within a portion of the 100-year floodplain) that must be reserved in order to discharge the 100-year flood without cumulatively increasing the water surface elevation more than one foot above the 100-year flood elevation before encroachment into the 100-year floodplain.

System configuration using internal design features and devices to moderate peak inflows by restricting the discharge rate to the next component; see also flow equalization.

System configuration using storage capacity to moderate peak flows over time and decrease the discharge rate to match the hydraulic or organic capacity of downstream components; see also flow attenuation and dosing, time.

Dosing tank that provides storage of effluent and uses time dosing for uniform delivery to a subsequent component over time, usually a day or more; also known as a surge tank.

Any method used to accurately quantify the flow of liquid.

Device that measures the instantaneous and/or cumulative amount of liquid that passes a designated point and is delivered to the next component.

Baffle designed to moderate discharge rate.

See distribution device.

Body of water that has been created by deliberately flooding an area.

Process of using effluent to scour a component and transport accumulated materials.

Toilet consisting of a bowl (for receiving human waste) and a water-flushing device.

Action of using effluent to scour a component and transport accumulated materials.

Orifice that controls the expelling of effluent and accumulated materials from a distribution system.

Valve used to control the expelling of effluent and accumulated materials from a distribution system.

Media filter that utilizes an open-cell polyurethane foam material that is randomly arranged in prefabricated modular units.

Constituent of sewage typically originating from foodstuffs (animal fats or vegetable oils) or consisting of compounds of alcohol or glycerol with fatty acids (soaps and lotions), typically measured in mg/L.

Plan view of the area and geometry of a system.

The hillslope position that forms the inner, concave surface at the base of a slope, and situated between the backslope and a toeslope; see also summit, shoulder, backslope, and toeslope.

Part of a collection system consisting of the piping that conveys sewage under pressure from a lift station to either a treatment system or a location where gravity flow can be used for conveyance.

Rod reading taken on a point of unknown elevation; foresight reading is subtracted from the Height of Instrument (HI) to determine the elevation of the desired point.

The average flow generated at the dwelling that passes completely through the system to the soil treatment area.

Natural or prepared ground or base on which some structure rests.

Valve that controls the effective action of the pump associated with a cargo tank; valve either directs the air flow into the cargo tank to create pressure or it directs the flow out of the cargo tank to create a vacuum.

Dense, brittle, usually acid subsoil horizon which limits the movement of water, air, and roots; extreme density and compactness is not a result of high clay content but of a dense soil fabric arrangement and/or cementation by various chemical constituents.

Quantity of hypochlorous acid (HOCl) and hypochlorite ions (OCl -) present after the introduction of chlorine for disinfection purposes; the relative distribution of these is affected by pH and temperature with lower pH favoring hypochlorous acid which has significantly higher germicidal efficiency than hypochlorite ions.

The part of a hillside or mountainside consisting of an outcrop of bare rock (scarp or cliff) that sheds colluvium to slopes below and commonly stands more steeply than the angle of repose of the colluvial slope (e.g., talus slope) immediately below.

Constructed wetland in which wastewater is exposed at the surface of the media.

A critical safety margin, representing the vertical distance between the normal operating water level (or flood level) and the top of a containment structure, channel, or vessel, that prevents overflow from waves, surges, or unexpected rises; see also head space.

See interceptor drain.

Component of total dynamic head (TDH) described as the sum of all friction loss in the piping network and associated devices; see also friction loss.

Reduction in pressure of liquid flowing through piping and associated devices as a result of contact between the liquid and the pipe walls, valves, and fittings.

Baffle designed to direct gases and rising solids away from the bottom of the outlet.

Valve employing a gating mechanism to control flow of fluid; gates may be of a plate design located in slots and opened either fully or partially.

A type of average, calculated as the       n^throot of the product of      n                  values. For example, if ten measurements were taken, the geometric mean of those measurements would be the 10^th        root of the product of those ten measurements

1. Synthetic fabric installed over distribution media to prevent migration of fine material; 2. Synthetic fabric used to control soil erosion and/or weed growth.

Valve consisting of a movable disk-type element and a stationary ring seat in a generally spherical body; often used for throttling.

Substance used in conjunction with a primer in the solvent welding process; see also primer.

Discrete sample collected at a particular time and location.

Graphical representation of the results of a sieve analysis; see also sieve analysis.

Rate of rise or fall along a specified line; grade is the same as slope; can be expressed in percent (as feet of rise or fall per 100 feet of horizontal distance), as a decimal equivalent as feet of rise or fall per foot or horizontal distance, or as a ratio.

Elevation of the bottom of an excavated trench, ditch, or other finished surface; the term ‘grade’ is sometimes used to denote the elevation of the finished surface of an engineering project.

Stake indicating the amount of cut or fill required to bring the ground to a specified level.

Soil structure descriptor for soil consisting of gravel, sand, or silt, (coarse grained textures) with little or no clay content; granular soil has no cohesive strength; some moist granular soils exhibit apparent cohesion; granular soil cannot be molded when moist and crumbles easily when dry.

Gravel, sand, or silt, (coarse grained soil) with little or no clay content; granular soil has no cohesive strength; some moist granular soils exhibit apparent cohesion; granular soil cannot be molded when moist and crumbles easily when dry.

Natural or constructed watercourse or outlet that is shaped or graded and established with suitable vegetation to minimize erosion during periods of surface water runoff.

Rounded or subrounded rock fragment that is between 0.1 inch (2 millimeters) and 3 inches (76 millimeters) in diameter.

Distribution medium consisting of perforated, corrugated pipe encased in a geotextile wrap.

Of or pertaining to measurement by weight.

Using the force of gravity to convey wastewater or effluent to one or more components or devices; gravity distribution to trenches may be parallel, sequential or serial; see also parallel distribution; sequential distribution; and serial distribution.

Primary collection piping placed on a carefully controlled grade; used for conveyance of wastewater via gravitational force.

Water captured from non-food preparation sinks, showers, baths, spa baths, clothes washing machines, and laundry tubs; see also blackwater.

Watertight device designed to intercept, congeal, and retain or remove fats, oils, and grease (FOGs) from food-service wastewaters; may be located inside (grease separator) or outside of a facility that generates commercial food service wastewater.

Mechanical grease interceptor usually associated with a plumbing unit and located within a facility that physically separates grease from the liquid, retaining the grease and discharging the liquid.

See grease interceptor.

See grease interceptor.

See graywater.

Centrifugal pump with blades at the intake that shreds solids in a waste stream and conveys the resulting mixture under pressure to a subsequent system component.

Safety device that quickly interrupts the flow of electric current in a circuit when it detects a ground fault or leakage to prevent electric shock hazards.