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Oklahoma Administrative Code (Last Updated: March 11, 2021) |
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TITLE 252. Department of Environmental Quality |
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Chapter 656. Water Pollution Control Facility Construction Standards |
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Subchapter 19. Sludge Facility Standards |
SECTION 252:656-19-5.1. Lime stabilization
Latest version.
- Alkaline material may be added to liquid primary or secondary sludges for: sludge stabilization in lieu of digestion facilities; to supplement existing digestion facilities; or for interim sludge handling. The design of the lime stabilization system shall account for the increased sludge quantities for storage, handling, transportation, and disposal methods and associated costs.(1) Operational criteria. Sufficient alkaline material shall be added to liquid sludge in order to maintain a homogeneous mixture with a minimum pH of 12 after 2 hours of vigorous mixing. Facilities for adding supplemental alkaline material shall be provided to maintain the pH of the sludge during interim sludge storage periods.(2) Odor control and ventilation. Odor control facilities shall be provided for sludge mixing and treated sludge storage tanks. Ventilation is required for indoor sludge mixing, storage and processing facilities. Provide 12 complete air changes per hour.(3) Tanks. Mixing tanks shall be designed to operate as either a batch or continuous flow process. The following items shall be addressed in determining the number and size of tanks:(A) peak sludge flow rates;(B) storage between batches;(C) dewatering or thickening performed in tanks;(D) repeating sludge treatment due to pH decay of stored sludge;(E) sludge thickening prior to sludge treatment; and(F) type of mixing device used and associated maintenance or repair requirements.(4) Equipment. Mixing equipment shall be designed to provide vigorous agitation within the mixing tank, maintain solids in suspension and provide for a homogeneous mixture of the sludge solids and alkaline material. Mixing shall be accomplished either by diffused air or mechanical mixers. If diffused aeration is used, an air supply of 30 cfm per 1,000 cubic feet of mixing tank volume shall be provided with the largest blower out of service. When diffusers are used, the nonclog type is required, and shall be designed to permit continuity of service. If mechanical mixers are used, the impellers shall be designed to minimize fouling with debris in the sludge and provide continuity of service during freezing weather conditions.(5) Feed and slaking equipment. Feed and slaking equipment shall be sized to handle a minimum of 150% of the peak sludge flow rate including sludge that may need to be retreated due to pH decay.