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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 626. Public Water Supply Construction Standards |
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Subchapter 9. Treatment |
SECTION 252:626-9-2. Pretreatment
Latest version.
- (a) Provide pre-sedimentation basins for package and slow sand filter water treatment plants if the raw water turbidity is variable and exceeds 30 NTU at any time during the year. Surface water containing an excessive amount of suspended material or high organic content which cannot be readily removed by a package treatment plant or slow sand filtration requires pre-sedimentation and may require additional treatment prior to conventional treatment.(b) Pre-sedimentation basins shall be designed in accordance with OAC 252:626-9-8.(c) Provide pre-sedimentation for microfiltration and ultrafiltration (MF/UF) for removal of total organic carbon or other soluble compounds, including, but not limited to iron and manganese. If the engineering report demonstrates that total organic carbon will not cause disinfection by-products violations then pre-sedimentation is not necessary. Other pretreatment methods, other than pre-sedimentation, shall be based on the results of a three (3) month pilot study. The study shall also determine the need for additional treatment if the water is high in turbidity or includes undesirable soluble constituents such as iron and manganese.(d) Pretreatment for nanofiltration and reverse osmosis (NF/RO) depends on the quality of the raw water. If the feed water has a turbidity of less than 1 NTU or an SDI of less than 5, then cartridge filters with a pore size range of less than 20 µm are required prior to the NF/RO treatment. If the feed water turbidity is 1 NTU or greater or the SDI is 5 or greater, then a more rigorous method of particulate removal, such as conventional treatment (including media filtration) or MF/UF membranes for particle removal is required. The use of MF/UF for pretreatment is more commonly known as an integrated membrane system (IMS). The IMS is one method allowed for the removal of particulate matter and microorganisms as well as some dissolved contaminants such as hardness, iron and manganese or disinfection by-product (DBP) precursors.