Decentralized Wastewater Glossary

A deposit on the earth of hail, mist, rain, sleet, or snow

Proactive maintenance strategy that uses data analysis to anticipate potential equipment malfunction and schedule maintenance proactively to minimize downtime, reduce maintenance costs, and optimize equipment lifespan by addressing issues before they escalate into major breakdowns.

Minimum specific physical standards or specifications for design, siting, and construction of system components.

Emitter designed to deliver effluent at a consistent flow rate under a range of operating pressures above a threshold.

Using a pump or siphon to convey wastewater effluent under pressure to one or more components or devices.

Change in pressure between two points in an operating system as a result of friction and/or a change in elevation; also known as head loss.

Primary supply line for pressurized transport or distribution of water or effluent; see also supply line.

Valve that limits pressure to a preset level by exhausting surplus air or water volume, thereby assuring that the permissible operating pressure is not exceeded.

Sewage collection system using a basin or tank for collection of sewage or effluent with subsequent conveyance under pressure to downstream system components; typical maintenace access includes cleanouts located in the piping network; includes alternative collection appurtenances such as septic tank effluent pump (STEP) and grinder or ejector pump basin systems.

Device that senses pressure, converting that information to an electrical signal; an associated microprocessor then converts the signal to a measurement of pressure, depth, or flow.

Delivery of effluent under pressure to a component or device; see also distribution, pressure-dosed gravity.

Gravity distribution of effluent over an infiltrative surface via one or more trenches or a bed following pressure dosing to a manifold or other distribution device; also known as ‘pump to gravity’.

Valve designed to maintain a set pressure on the downstream side of the valve regardless of pressure changes on the upstream or source side.

Portion of a dosing event during which the distribution system is full and thus at operating pressure.

Portion of a dosing event during which the distribution system is being filled and thus is not yet at operating pressure.

Any component or combination of components that provides treatment of wastewater primarily through sedimentation (floatation and settling).

Proactive maintenance strategy utilizing scheduled, time-based or usage-based approach to conducting activities, e.g., maintenance tasks at predetermined intervals (e.g., every three months or after 500 operating hours).

First of two automatic shut-off valves that prevent the tank from being overfilled.

Physical treatment processes involving removal of particles, typically by settling and flotation with or without the use of coagulants; (e.g. a grease interceptor or a septic tank provides primary treatment); see also physical treatment.

1. Act of initiating pump operation by filling the pump housing with liquid; 2. Air pressure under the bell of a siphon that allows it to operate properly.

substance used in conjunction with glue in the solvent welding process; see also glue.

Soil structure descriptor for soil aggregates with prismlike shapes exhibiting a vertical axis much longer than the horizontal axes.

See pit toilet.

Maintenance strategy focusing on preventing equipment malfunctions by performing activities such as periodic checks, inspections and routine maintenance tasks; activities focus on identification and mitigation or elimination of the root cause of malfunctions.

A sequential flow of treatment processes configured as a treatment train to achieve removal of target constituents.                  

Recording data on equipment condition and process parameters using sensors, recording devices, meters, etc. to determine process operational conditions to facilitate identification of deviations from normal operation.

Term applied to a septic tank when it is configured to receive a combination of raw sewage and recirculated effluent to enhance nitrogen removal.

Method of finding the elevations of a series of points at measured, horizontal distances along a line or path; process used in the development of a topographic map.

Legal boundary defining land parcels.

Finish grade as specified on a plan.

Held under patent, trademark, or copyright.

Method of protecting employees from cave-ins, from material that could fall or roll from an excavation face or into an excavation, or from the collapse of adjacent structures. protective systems include support systems, sloping and benching systems, shield systems, and other systems that provide the necessary protection.

Organism, usually unicellular and heterotrophic, that lives in aquatic and terrestrial habitats; pathogenic species are a constituent of concern in biological wastewater treatment systems.

See pressure-regulating valve.

Acronym for expressing pressure in units of pounds per square inch

Bacteria which grow best at temperatures between 10- and 30-degrees C (50- and 86-degrees F) with optimum growth between 12- and 18-degrees C (54- and 64- degrees F).

Power take-off.

Mechanical device for driving fluid flow or for raising or lifting fluid by either suction or pressure or both.

Shallow open container installed in a dosing tank; the container houses the pump and effectively raises the pump intake level to the lip of the basin.

Flow (gpm) a pump can deliver at a certain operating pressure (head).

Graphical method that describes the relationship between the total dynamic head (TDH) and the capacity of pumps using various size impellers; the curve also includes information about efficiency and horse power consumption.

Flow delivered by a pump at a specified total dynamic head expressed as volume per unit time.

Point of liquid entry into a pump housing.

See lift station.

Tank or compartment which provides storage of effluent and contains a pump and associated appurtenances used to convey effluent to another treatment process or a final treatment and dispersal component; see also dosing tank and siphon tank.

Device installed in a septic or dosing tank that houses a pump and screens effluent before it enters the pump.

Dosing tank that collects and stores groundwater from a subsurface drainage system and convey collected groundwater to a stabilized drainage outlet using a demand dosing configuration.

Service provider who removes and disposes of septage from a wastewater treatment component according to specific regulatory parameters.

1. Act of removing septage from a wastewater treatment system component; 2. Conveying effluent under pressure.

Polyvinyl chloride

One who, by possession of a recognized degree, certificate, or professional standing, or who with extensive knowledge, training and experience, has successfully demonstrated his ability to solve or resolve problems relating to the subject matter, work, or project; see also competent person.

1. Device that allows removal of another device without cutting the associated piping; 2. Mechanical device that allows interruption of electrical power.

Pump in which the impeller is a turbulent mixer that causes tank liquid to flow perpendicular to the impeller's axis of rotation; types of radial flow impellers include disk-style flat blade turbines and curved blade turbines; used in applications where high shear rates are needed, such as in dispersion processes.

Device located within a dosing tank that supports the pump and facilitates its removal or replacement.

Inclined walking or working surface that is used to gain access to one point from another and is constructed from earth or from structural materials such as steel or wood.

Long pole with painted red and white delineations of one foot each; used to mark points that are difficult to see from a distance.

See sewage.

Any wastewater leaving a source; see also sewage.

Rotating biological contactor.

Second step in the sequential treatment processes that occur in a sequencing batch reactor or SBR.

The opposition to an alternating current caused by inductance and capacitance in an electrical circuit, equal to the difference between capacitive and inductive reactance. Expressed in ohms.                           

Maintenance strategy where activities are only performed in response to component malfunction.

Container or tank in which controlled chemical and biological reactions used for the treatment of wastewater are carried out.

Volume of effluent returned to a preceding treatment train component over a specific period.

Design configuration wherein a portion of effluent is returned to a component for further treatment or to facilitate a treatment process.

A media filter configuration wherein a portion of the effluent is returned to an upstream component.

See recirculating media filter.

Valve that contains a floating ball that rises when the tank level rises and prevents more water from entering the tank; when the water level drops, the ball drops and allows water to flow into the tank again.

The act or process of circulating again or causing something to circulate again.

Volume of effluent returned to the recirculation tank compared to the volume of forward flow to the next component of the treatment train; calculated by dividing the recirculated volume by the forward flow volume ([total dosed volume – forward flow volume] / forward flow volume); see also circulation ratio and forward flow.

Dosing tank that mixes effluent from two or more components within the treatment train and allows a portion of partially treated effluent to pass through one or more treatment components again.

piping configuration in a pump discharge assembly to return a portion of the flow back into the dosing tank to change the system duty point, adjust system operating pressure or mix the contents of a tank.

See water reclamation.

Professionally drafted written plan produced by the designer that incorporates installer-documented modifications, substitutions and deviations made during construction. See also as-built drawing.

See water recycling.

Zones of apparent accumulation of Fe (iron) and/or Mn (manganese) oxides in soils.

Zones of low chroma where Fe (iron) and/or Mn (manganese) oxides and/or clay have been stripped out of the soil.

Electrical potential (measured in volts or millivolts) of a system due to the tendency of the substances in it to give up or acquire electrons.

Soil property that results from the reduction and oxidation of iron and manganese compounds in the soil after saturation with water and subsequent desaturation; see also redox concentration and redox depletion.

Addition of electrons to a chemical entity decreasing its valence or oxidation number; for example, under anaerobic conditions (no dissolved or molecular oxygen (O₂) present), sulfur compounds are reduced to produce hydrogen sulfide (H₂S) and other compounds; see also oxidation.

Duplicate processes in parallel or sequential operation that facilitate continued operation when one of the processes malfunctions.

1. Optional operating parameter in a time dosed configuration that acts as a fail-safe by preventing pump operation when effluent levels reach a specified level below the normal off level; 2. Sensor that controls the redundant off function in a time dose system; typically, this sensor is directly wired into the pump circuit, thus bypassing the timer or control circuits; 3. In a programmable system, the redundant off float allows the timer “on” cycle to continue even though the timer enable float deactivates; the configuration is intended to reduce the occurrence of short cycling in pumps.

Official, permanent point of known elevation; see also monument.

Person who is registered as a professional engineer in the state where the work is to be performed; a professional engineer, registered in any state is deemed to be a "registered professional engineer" within the meaning of this standard when approving designs for "manufactured protective systems" or "tabulated data" to be used in interstate commerce.

The extent to which a system provides consistent treatment; requires a resilient design, integrates redundancy and includes a proactive maintenance approach.                      

Proactive maintenance strategy that focuses on understanding the functions and potential failure modes of equipment to determine the most effective maintenance approach; prioritizes maintenance efforts on critical components to ensure overall system reliability.

Configuration of non-perforated piping and a drop box that conveys effluent to the next trench; see also cross-over pipe and stepdown.

1. Non-perforated piping used to convey excess effluent to succeeding trenches; 2. Non-perforated piping used to convey effluent to the receiving environment; an NPDES permit is typically associated with the discharge to drain tile, ditches or waterways.

Act or process of correcting a fault or deficiency without changing system structure or form.

Remote access to and storage of real-time data associated with process information such as equipment condition and process parameters; includes the ability to identify deviations from normal operation and notify interested parties; see also                                  predictive maintenance.

Fixing or replacing substandard or damaged components; repairs can be categorized as required repairs, recommended repairs, and upgrades and may require a permit from a regulatory authority.

See reserve area.

Process of exchanging a component with an equivalent component.

Act of submitting a detailed report of inspection, monitoring or operation and maintenance activities performed on a wastewater treatment system.

Area of land with demonstrated capacity for use as a final treatment and dispersal component upon which no permanent structure should be constructed and which is intended for replacement of the original system if needed.

Extra treatment capacity built into wastewater collection, treatment, and dispersal components or systems to accommodate projected increases in flow.

Volume in the head space of a dosing tank between alarm on elevation and the invert of the inlet pipe; intended for temporary storage of effluent in the event of component malfunction or excessive flow.

See detention time.