Texas Administrative Code (Last Updated: March 27,2024) |
TITLE 30. ENVIRONMENTAL QUALITY |
PART 1. TEXAS COMMISSION ON ENVIRONMENTAL QUALITY |
CHAPTER 217. DESIGN CRITERIA FOR DOMESTIC WASTEWATER SYSTEMS |
SUBCHAPTER G. FIXED FILM AND FILTRATION UNITS |
SECTION 217.190. Filtration
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(a) Reasons for Use. (1) Permit Requirements. A wastewater treatment facility that requires tertiary effluent limitations must use filtration as a unit of operation to supplement suspended solids removal. Tertiary effluent limits are any limits less than or equal to five milligrams per liter for five-day biochemical oxygen demand or total suspended solids. (2) Specific Water Quality Requirements. A wastewater treatment facility designed for secondary or advanced secondary treatment effluent limitations may use filtration as a unit of operation to supplement suspended biological floc removal. Filters may be designed for intermittent operation if filters are not necessary to meet permitted effluent limitations. (b) Redundancy. (1) A wastewater treatment facility using filtration to provide tertiary treatment to comply with a permit requirement must have a minimum of two independent, fully functional filter basins with independent, fully functional equipment. (2) The design of a filtration system must specify the submerged filter surface area required to treat the peak flow with the largest filter unit out of service. (3) If a filter is provided solely to polish wastewater in situations where permit compliance does not depend on the use of a filter, such as in some cases of reclaimed water use, one filter is allowed. (c) Source of Backwash Water. A filtration system must use filtered effluent as the source of backwash water. (d) Disposition of Backwash Water. A filtration system must return backwash water containing material cleaned from a filter to the headworks of the wastewater treatment facility or to the influent lift station for processing. (e) Sequence of Treatment Units. (1) A final clarifier must precede a filter. (2) A filter system may be used in conjunction with a disinfection tank to provide additional detention time, provided the filter is backwashed to the headworks of the wastewater treatment facility or to the influent lift station. (f) Overload Conditions. A design must prevent effluent or partially treated effluent from overflowing from any filtration unit. (g) Control of Slime Growth. A filtration system must provide periodic disinfectant in the influent stream to control slime growth in the filter and backwash storage tank. Source Note: The provisions of this §217.190 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254