SECTION 217.122. Fine Screening Devices

(a) A fine screen may be used in lieu of a coarse screen.

(b) The clear openings in a fine screen must be less than 0.25 inch.

(c) Any five-day biochemical oxygen demand (BOD₅ ) reduction percentage claimed for a fine screen must be developed through a study conducted on actual full-scale operation of the proposed fine screen. The BOD₅ reduction percentage claimed must not exceed 35%.

(d) The engineering report must justify any reduction in the size of a treatment unit that is based on removal of BOD₅ by a fine screen.

(e) An owner who claims a BOD₅ reduction credit must include a sufficient number of fine screen units so that any BOD₅ reduction claimed will be met with the largest fine screen unit out of service.

(f) A design may include a single fine screen unit only if the design includes an emergency overflow channel with a coarse screen to accept flow when the fine screen is out of service. No BOD₅ removal credit is allowed with a single fine screen design.

(g) A coarse screen must be provided ahead of a fine screen when the manufacturer of a fine screen recommends prescreening before the fine screen.

(h) A moving or rotating fine screen must use a continuous cleaning device, such as water jets or wiper blades.

(i) A fine screen unit must automatically convey the screenings to a storage area or processing unit that complies with §217.123 of this title (relating to Screenings and Debris Handling).

(j) A fine screen must meet the manufacturer's recommendations with respect to velocity and head loss through the fine screen.

(k) A fine screen must use either a bar rack or a perforated plate.

Source Note: The provisions of this §217.122 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254