Administrative Code

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Virginia Administrative Code
Title 9. Environment
Agency 25. State Water Control Board
Chapter 860. Virginia Pollutant Discharge Elimination System General Permit Regulation for Potable Water Treatment Plants

9VAC25-860-10. Definitions.

The words and terms used in this regulation shall have the meanings defined in the State Water Control Law and 9VAC25-31, the VPDES Permit Regulation, unless the context clearly indicates otherwise, except that for the purposes of this chapter:

"Board" means the State Water Control Board. When used outside the context of the promulgation of regulations, including regulations to establish general permits, "board" means the Department of Environmental Quality.

"Department" or "DEQ" means the Virginia Department of Environmental Quality.

"Conventional filtration treatment" means a series of processes including coagulation, flocculation, sedimentation, and filtration resulting in substantial particulate removal.

"Membrane treatment" means a pressure or vacuum driven process using synthetic materials to separate constituents from water. Membranes are used for dissolved solids or suspended solids removal. Membrane treatment for dissolved solids removal includes reverse osmosis and nanofiltration. Membrane treatment for suspended solids removal includes ultrafiltration and microfiltration.

"Microfiltration" means a method of membrane treatment designed to remove particles down to 0.1 µm in size. The treatment removes cysts, bacteria, and most (but not all) particulates.

"Nanofiltration" or "low-pressure reverse osmosis" or "membrane softening" means a method of membrane treatment designed to remove multivalent ions (softening) and removes contaminants down to 1 nm (nanometer = 0.001 µm) in size.

"Potable water treatment plant" means an establishment engaged in producing water for domestic, commercial, or industrial use as designated by North American Industry Classification System (NAICS) Code 221310 - Water Supply and Irrigation Systems, (Executive Office of the President, Office of Management and Budget, United States, 2017), Standard Industrial Classified (SIC) Code 4941 - Water Supply (Office of Management and Budget (OMB) SIC Manual, 1987), or others as approved by the department.

"Reverse osmosis" means a method of membrane treatment designed to remove salts and low-molecular weight solutes and remove all contaminants down to 0.0001 µm (microns) in size. Reverse osmosis methods apply pressure in excess of osmotic pressure to force water through a semi-permeable membrane from a region of high salt concentration to a region of lower salt concentration.

"Total maximum daily load" or "TMDL" means a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards and an allocation of that amount to the pollutant's sources. A TMDL includes wasteload allocations (WLAs) for point source discharges, and load allocations (LAs) for nonpoint sources or natural background or both, and must include a margin of safety (MOS) and account for seasonal variations.

"Ultrafiltration" means a method of membrane treatment designed to remove particles down to 0.01 µm in size. The treatment removes cysts, bacteria, and viruses as well as suspended solids.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia; § 402 of the Clean Water Act.

Historical Notes

Derived from Virginia Register Volume 25, Issue 6, eff. December 24, 2008; amended, Virginia Register Volume 29, Issue 23, eff. December 24, 2013; Volume 34, Issue 11, eff. July 1, 2018; Volume 39, Issue 4, eff. November 9, 2022: Volume 39, Issue 11, eff. July 1, 2023.

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