SECTION 217.2. Definitions

The following words and terms, when used in this chapter, have the following meanings unless the context clearly indicates otherwise.

(1) Activated sludge--A collection of actively growing biological organisms that results from combining wastewater, organisms, and air in an aerated treatment process.

(2) Activated sludge process--A biological wastewater treatment process in which activated sludge is aerated. The activated sludge microorganisms are subsequently separated from the wastewater and wasted or returned to the process.

(3) Advanced nutrient removal--A process to remove phosphorus, nitrogen, or both, that is intended to produce higher quality effluent than is normally achieved by secondary treatment processes.

(4) Air gap--The unobstructed vertical distance through the free atmosphere between the lowest opening from any pipe or faucet conveying water to a tank, fixture, receptor, sink, or other assembly and the flood level rim of the receptacle. To qualify as an air gap under this chapter, the vertical, physical separation must be at least twice the diameter of the water supply outlet, but never less than 1.0 inch.

(5) Alter or alteration--

(A) To replace a treatment unit or a collection system unit.

(B) To modify a treatment unit, a collection system unit, or an associated appurtenance, in a way that changes any of the following for a treatment unit or collection system unit:

(i) the capacity;

(ii) the intended function;

(iii) the process;

(iv) the mode of operation;

(v) the configuration;

(vi) a design parameter;

(vii) a major design assumption; or

(viii) the function of any other treatment unit or collection system unit.

(6) Alternative collection system--A collection system that uses components such as grinder pumps, septic tanks, or vacuum valves, which are installed throughout the collection system, specifically including the types of collection systems identified in Subchapter D of this chapter (relating to Alternative Collection Systems). An alternative collection system is comprised of both on-site and off-site components.

(7) Annual average flow--The arithmetic average of all daily flow determinations taken within a period of 12 consecutive months.

(8) Appurtenance--An appliance or a component associated with a treatment unit or collection system unit that is not considered integral to the identity of the unit.

(9) Auxiliary pump--A secondary or supplementary pump that is available for use as needed.

(10) Biotower--A biological filtration system that involves biological film on a plastic media that reduces the biochemical oxygen demand of the effluent.

(11) Building lateral--A pipe that conveys raw wastewater and connects the plumbing of a structure to a collection system pipe. For an alternative collection system, a pipe that conveys raw wastewater and connects the plumbing of a structure to an on-site component (e.g., grinder pump, vacuum valve pit, septic tank effluent pump). A building lateral is not a part of a collection system.

(12) Bypass--The intentional diversion of a waste stream from any portion of a wastewater treatment facility or collection system.

(13) Collection system--Pipes, conduits, lift stations, force mains, and all other constructions, devices, and appurtenant appliances used to transport domestic wastewater to a wastewater treatment facility.

(14) Collection system unit--A part of a collection system that performs a basic step in the transport of wastewater to a wastewater treatment facility, provides access to the collection system, or is an integral safety feature of the collection system (e.g., pipeline, lift station, manhole, air release valve, etc.).

(15) Completely mixed aerated lagoon--A lagoon in which oxygen is supplied mainly through mechanical or diffused aeration, and in which the aeration system is designed to keep solids in suspension.

(16) Construct--To build, erect, place, assemble, remodel, alter, or otherwise create a treatment unit, a collection system unit or an associated component or appurtenance of a treatment unit or collection system unit. For purposes of this chapter, construction also includes installation of fencing, excavation, site preparation, and placement of skid-mounted or modular units.

(17) Constructed wetland--A wastewater treatment unit designed to replicate the processes that occur in natural wetlands. Constructed wetlands are complex, integrated systems in which wastewater, plants, animals, microorganisms, and the environment (including sun, soil, and air) interact to improve water quality.

(18) Day--A period of 24 consecutive hours beginning at 12:00 a.m. local time.

(19) Decanter--A device used to draw off liquid without disturbing solids that are in the process of sedimentation.

(20) Design flow--The highest anticipated 30-day average flow rate.

(21) Design life--The length of time that an engineered structure or device is intended to function without failing.

(22) Diurnal flow--The daily cycle of high and low influent flows to a wastewater treatment facility.

(23) Domestic wastewater--Wastewater which originates primarily from kitchen, bathroom, and laundry sources, including waste from food preparation, dishwashing, garbage grinding, toilets, baths, showers, and sinks of a residential dwelling. Domestic wastewater may contain commercial or industrial wastewater contributions.

(24) Dry Well--The portion of a pumping station where non-submersible pumps and controls are housed separately from the liquid being pumped.

(25) Effective size--The particle diameter that represents the smallest 10th percentile of a sample of filter media particles on a mass basis. In other words, 10% of the sample mass consists of particles that are smaller than the effective size and 90% of the sample mass consists of particles that are larger than the effective size.

(26) Effluent--Liquid that flows out of a process or confined space. This term may also be used to identify items or properties associated with effluent (e.g., effluent constituents, effluent limits, or effluent pump).

(27) Emergency overflow--A conduit or spillway designed to prevent an unauthorized discharge of wastewater by redirecting excess flow for processing in a treatment unit.

(28) Engineer--A professional engineer, licensed by the Texas Board of Professional Engineers, with expertise in design and construction of wastewater treatment facilities and collection systems.

(29) Engineering Report--The final engineering design report prepared, signed, and sealed by the engineer. The report must include calculations and written descriptions of processes, equipment, and structures that demonstrate compliance with this chapter, as described in §217.10 of this title (relating to Final Engineering Report) and as required throughout this chapter.

(30) Equalization basin--A treatment unit designed primarily to dampen fluctuations of flow or concentration before wastewater flows into a subsequent treatment unit.

(31) Equivalent dwelling unit--Any building or section of a building that produces wastewater of a composition and quantity equal to that discharged by a single, private residence. For calculation purposes, an equivalent dwelling unit is occupied by 3.5 individuals, unless a different number is justified by actual data.

(32) Filter media--The material placed in a filter containment structure to separate solids from a liquid.

(33) Firm pumping capacity--The maximum flow rate achievable, under design conditions, with the largest pumping unit out of service.

(34) Force main--A pressure-rated conduit that conveys wastewater from a lift station.

(35) Free water surface wetland--A constructed wetland designed to have the water surface above the wetland bed or substrate.

(36) Gravity relief sewer--A part of a collection system built to manage the flow of wastewater that exceeds the capacity of the existing collection system.

(37) Grinder pump--A collection system unit that receives raw wastewater, grinds the solids in the wastewater into a slurry, and provides the motive force for transporting the slurry to a lift station or a collection system.

(38) Headworks--The location where wastewater enters a wastewater treatment facility and preliminary treatment occurs, typically by removing large solids or grit.

(39) Influent--Liquid that flows into a process or confined space. This term may also be used to identify items or properties associated with influent (e.g., influent constituents, influent limits, or influent pump).

(40) Innovative technology--A process, method, product, or material not addressed in this chapter or a process specifically identified as innovative by this chapter.

(41) Interceptor tank--A collection system unit that receives raw wastewater, removes floatable and settleable solids, stores the removed solids, and provides flow attenuation.

(42) Lift station--A structure that collects wastewater and uses pumps to raise it to a higher elevation. The term lift station applies to a structure in which the static head exceeds the frictional head losses.

(43) Maintenance--The scheduled preventative care, repair, or equivalent replacement of components or appurtenances of a treatment unit or a collection system unit (e.g., replacing a pump with an equivalent pump - not replacing an entire lift station, and not replacing a pump in a lift station with a pump that will operate at a different flow rate or pressure). Replacement must not cause alteration, as defined in this chapter. Maintenance does not include replacement of a treatment unit or a collection system unit.

(44) Membrane bioreactor system--An activated sludge process that uses membrane filtration rather than clarification to remove solids.

(45) Minimum grade effluent sewer--An alternative collection system pipeline with a constant downward slope that transports effluent from an interceptor tank by gravity flow.

(46) Multiple equivalent dwelling unit--Either:

(A) a group of two or more residences served by a common service connection; or

(B) a commercial, industrial, institutional, or other non-residential establishment that produces wastewater:

(i) in excess of 1,500 gallons per day; or

(ii) not comparable in composition to that discharged by a single private residence.

(47) Non-conforming technology--Technology or a process that does not conform to the design criteria of this chapter or a technology or process specifically identified as non-conforming in this chapter.

(48) Off-site component--A collection system component that includes collection system pipes, force mains, pump stations, lift stations, vacuum stations, and related appurtenances not located at a wastewater treatment facility.

(49) On-site component--Alternative collection system equipment placed on private property.

(50) Overflow--An unauthorized flow of untreated or partially treated wastewater from a collection system or from a treatment unit at a wastewater treatment facility.

(51) Owner--A person who owns a collection system or a wastewater treatment facility or part of a collection system or wastewater treatment facility. For the purposes of this chapter, "owner" refers to the owner and to the owner's representatives, agents, and designees (for example, an operator, an engineer, a staff member, a contractor).

(52) Partially mixed aerated lagoon--A lagoon in which oxygen is supplied mainly through mechanical or diffused aeration, in which the aeration system is designed to allow solids to settle out of suspension.

(53) Peak flow--The highest two-hour flow expected under any operational conditions, including times of high rainfall, based on a two-year, 24-hour storm or a prolonged period of wet weather.

(54) Plans--Construction drawings or other documents that show details of the design of a project.

(55) Preliminary treatment--Removal of wastewater constituents such as rags, sticks, floating material, and grit that may cause maintenance or operational problems in subsequent treatment units.

(56) Pressure sewer--A collection system that is pressurized by pumps at each service connection.

(57) Primary sedimentation unit--A treatment unit that removes solids from the wastewater by physical settling before the wastewater enters a unit that removes waste by biological conversion.

(58) Primary treatment--A physical treatment process, other than preliminary treatment, that removes biologically available wastewater constituents primarily by settling or floatation.

(59) Processing unit--A component of a wastewater treatment facility that performs a basic step in preparing sludge for disposal after the sludge has been separated from the wastewater (e.g., sludge thickener, digester, sludge drying bed, belt press). Processing units are considered a subset of treatment units for the purposes of this chapter.

(60) Project--A construction, repair, alteration, or rehabilitation of a collection system, a wastewater treatment facility, or an associated component, beginning with design initiation and ending with permanent decommissioning.

(61) Pump--A device that raises, transfers, or compresses fluids by suction, pressure, or both.

(62) Rehabilitate--To repair a collection system using a technology that is described in §217.56(c) of this title (relating to Trenchless Pipe Installation) or using any other lining or coating method.

(63) Re-rate--To change the design flow or design organic loading of a treatment unit, without altering the unit, based on actual performance data.

(64) Secondary treatment--The level of treatment defined as secondary treatment in §309.1(b) of this title (relating to Scope and Applicability).

(65) Sequencing batch reactor (SBR)--A fill and draw activated sludge treatment system where secondary aeration and secondary clarification processes are carried out sequentially in the same tank. An SBR system has the following five steps that are carried out in the following sequence:

(A) fill - the basin is filled with the influent;

(B) react - the influent in the basin is aerated;

(C) settle - the mixed liquor within the basin is settled (clarification);

(D) draw - the basin is decanted; and

(E) idle - the sludge is removed from the basin.

(66) Sludge stabilization--The process of destroying or inactivating pathogens in sludge and reducing volatile solids content.

(67) Small diameter effluent sewer--A collection system that receives effluent from an interceptor tank and transports the flow by gravity. A small diameter effluent sewer may include minimum grade and variable grade effluent sewers.

(68) Specifications--Precise standards of performance for construction work, materials, and manufactured products, which make possible the expression of expected value when they are purchased or contracted for and which provide means of determining their conformance with expectations after they are purchased or constructed.

(69) Stabilization lagoon--A shallow lagoon used to achieve secondary treatment through natural processes. In this chapter, "stabilization lagoon" is synonymous with "stabilization pond," "oxidation lagoon," and "oxidation pond."

(70) Subsurface flow wetland--A wetland system that maintains the water level below the surface of the gravel or other media placed in the wetland bed or cell.

(71) Summary transmittal letter--A letter submitted to the executive director that provides basic information about a project so that the executive director can determine whether to require a full review of the project plans and specifications.

(72) Surcharge--The hydraulic overloading of a portion of a gravity collection system. A surcharge causes wastewater to rise within manholes and may cause an overflow.

(73) Totalizing meter--A water measuring device that registers or accumulates total flow. The totalizing meter shall be non-resettable.

(74) Treatment unit--A component of a wastewater treatment facility that performs a basic step in the wastewater treatment process (e.g., lift station, bar screen, aeration basin, clarifier, chlorine contact chamber).

(75) Twenty-five-year, 24-hour rainfall event--The maximum rainfall event with a probable recurrence interval of once in 25 years, with a duration of 24 hours, as defined by the National Weather Service in Technical Paper Number 40, Rainfall Frequency Atlas of the United States, May 1961; or equivalent regional or state rainfall information.

(76) Two-year, 24-hour rainfall event--The maximum rainfall event with a probable recurrence interval of once in two years, with a duration of 24 hours, as defined by the National Weather Service in Technical Paper Number 40, Rainfall Frequency Atlas of the United States, May 1961; or equivalent regional or state rainfall information.

(77) Variable grade effluent sewer--A small diameter gravity collection system that does not require a uniform gradient, but will allow for both positive and negative gradients. A variable grade effluent collection system may be used with septic tank effluent pumps.

(78) Variance--A deviation from a specific requirement of this chapter. A variance requires executive director approval.

(79) Wastewater--A waterborne industrial waste, recreational waste, domestic waste, or combination of these wastes.

(80) Wastewater treatment facility--All contiguous land and fixtures, structures, and appurtenances used for storing, processing, and treating wastewater. A wastewater treatment facility does not include the collection system located outside of the fenced area around a wastewater treatment facility.

(81) Wasting--The practice of removing sludge from a wastewater treatment process.

(82) Weir overflow--The flow of liquid through or over a clarifier weir or a weir used for flow measurement.

(83) Wet well--A pumping station or a portion of a pumping station that stores the fluid being pumped. A wet well may be used in conjunction with a dry well, or may contain its own submersible pumps and equipment.

Source Note: The provisions of this §217.2 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254