Oklahoma Administrative Code
Title 252 - Department of Environmental Quality
Chapter 656 - Water Pollution Control Facility Construction Standards
Subchapter 17 - Clarifier Standards
Section 252:656-17-2 - Clarifier design considerations
Current through Vol. 41, No. 13, March 15, 2024
(a) Flow distribution. Effective flow splitting devices and control appurtenances (i.e. gates, splitter boxes, etc.) shall be provided to permit proper proportioning of flow and solids loading to each unit throughout the expected range of flows.
(b) Primary clarifier design criteria.Primary clarifiers shall be placed downstream of flow distribution devices. Surface settling rates for primary tanks shall not exceed 1,000 gal/ft2/day at design average flows or 1,500 gal/ft2/day for peak hourly flows. Peak hourly flow is based upon a 2-hour sustained peak, as defined by Wastewater Engineering: Treatment, Disposal & Reuse, Metcalf & Eddy, Inc. 4th Edition (2003). The primary clarifier must have a minimum side water depth of twelve feet (12'). Clarifier sizing shall be calculated for both flow conditions and the larger surface area determined shall be used. Primary settling of normal domestic sewage can be expected to remove 30 to 35% of the influent BOD. However, anticipated BOD removal for sewage containing appreciable quantities of industrial wastes (or chemical additions to be used) shall be determined by laboratory tests and consideration of the quantity and character of the wastes.
(c) Secondary clarifier design criteria. See Appendix B.
(d) Inlet structures. Design inlets to prevent short-circuiting, to dissipate velocity and diffuse flow equally across the entire cross-section of the settling chamber. Design channels to maintain a velocity of at least 1 fps at one-half design flow. When scum ports in the inlet diffusion well baffle are provided, the elevation of the bottom edge of the ports shall be no lower than 0.10 feet below the elevation of the crest of the overflow weirs.
(e) Weirs. Overflow weirs shall be adjustable and level.
Added at 17 Ok Reg 1140, eff 6-1-00; Revoked at 23 Ok Reg 937, eff 6-15-06; Added at 28 Ok Reg 1282, eff 7-1-11