2.1 Aerobic Treatment Unit (ATU): A mechanical on-site treatment unit that provides secondary wastewater treatment by mixing air and aerobic and facultative microbes with the wastewater. ATU's typically use a suspended growth treatment process or a fixed treatment process.

2.2 Air/Vacuum (A/V) Relief Valve: A valve that automatically lets air out of or into liquid carrying pipe as needed in response to changes in system pressure.

2.3 Aerobic: Having molecular oxygen as a part of the environment, or growing or occurring only in the presence of molecular oxygen.

2.4 Backwash: The process of flow reversal to clean a filter and to restore it to the normal clean condition for filtering with a minimum resistance to flow through the media or screen.

2.5 Control Panel: An electronic control panel that controls the quantity and time of dose. This can also control the zone receiving the effluent, automatically flushes the lines, flushes the filters, monitors the flow rates and pump run cycles or times.

2.6 Decentralized System: An onsite and/or cluster wastewater system used to treat and disperse or discharge small volumes of wastewater, generally from dwellings or businesses that are located relatively close together.

2.7 Disk Filter: A type of filter that utilizes a series of grooved rings that overlay each other to form a network of very small openings to trap contaminants.

2.8 Distributing Valve: A valve that distributes flow to multiple drain field laterals, zones or locations by automatically rotating upon each pump cycle.

2.9 Drain-back: The process of effluent draining along the laterals and manifolds after the pump shuts off. Drainage occurs both inside and outside the drip tubing and manifolds to lower elevations in the drip field.

2.10 Drip Line: Tubing constructed from polyethylene with emitters embedded regularly along the length of the tube.

2.11 Effluent: Sewage, water or other liquids, partially or completely treated or in its natural state flowing out of a septic tank, aerobic treatment unit, or other treatment system or systems.

2.12 Emitters: Small diameter openings in drip line that can dissipate pressure and allow a slow, controlled discharge normally rated in gallons per hour.

2.13 Field Flush: Water is passed through the drip lateral for the purpose of removing particles and other debris from the walls of the drip tubing. The flush water is carried back through the return manifold and return line to the pretreatment unit.

2.14 Filter: A device for the main purpose of removing suspended solids and other debris from the wastewater.

2.15 Hydraulic Conductivity: The rate of water movement under unit gradient in a specific soil horizon.

2.16 Interceptor Drain: A subsurface drain line, usually constructed upgrade from the absorption area to divert seasonal groundwater.

2.17 Lateral: One single run or multiple runs of drip tubing connected at one end to a supply manifold and the other end connected to a return manifold.

2.18 Maintenance Personnel: A individual certified by the Department to conduct assessments under the Onsite Maintenance and Monitoring Program.

2.19 Monitoring: Periodic inspection of system for performance.

2.20 Pressure Compensating (PC) Emitters: Drip emitters that allow a constant flow or discharge over a wide range of applied pressure.

2.21 Pressure Distribution: A system of small diameter pipes equally distributing effluent through a trench or bed.

2.22 Pressure Regulator: A device used to regulate and maintain a constant discharge pressure.

2.23 Pretreatment: The conditioning of effluent prior to dispersal by a drip system.

2.24 Return Line: The return line connects the return manifold to the pretreatment unit for the purpose of carrying flush water from the drip field.

2.25 Return Manifold: A collection manifold or piping that returns excessive wastewater and debris to the primary treatment tank during system flushes.

2.26 Run: One continuous length of tubing routed across contour connected to a supply line or return line or another run.

2.27 Soil Structure: The combination or arrangement of individual soil particles in definable aggregates, or peds, which are characterized and classified on the basis of size, shape, and degree of distinctness.

2.28 Solenoid Valve: An electric valve actuated by a solenoid, used for controlling the flow or liquid in pipes.

2.29 Spin Filter: A filter that consist of a screen cylinder enclose in a casing. The typical filter screen mesh size is 150 and a micron rating of 100.

2.30 Static Plow: A drip line plow with a shank that remains at a given depth as the plow is pulled through the soil.

2.31 Supply Line: The line that extends from the pump to the supply manifold of a given zone.

2.32 Supply Manifold: The supply manifold connects the supply line to the drip laterals.

2.33 Vertical Separation: The depth of unsaturated, original, undisturbed soil between the bottom of the drip tubing and highest seasonal water table or restrictive layer.

2.34 Vibratory Plow: A vibratory plow is a drip line plow with a shank that vibrates vertically as the plow is pulled through the soil.

2.35 Water Table: The level in saturated soil at which the hydraulic pressure is zero.

2.36 Zone: A group of laterals that are dosed at the same time.