Section NR 811.575 - Anion exchange The water system shall pretreat water when the content of iron, manganese, or a combination of both is 0.5 milligram per liter or more. The department may require a water system pretreat water when the content of iron, manganese, or a combination of both is less than 0.5 milligram per liter but pretreatment is necessary to protect public health. The water system shall satisfy all of the following requirements unless the department determines sufficient justification for alternative operational parameters is provided by the anion exchange vessel manufacturer or demonstrated through pilot testing under s. NR 811.44:
(1) The anion exchange units shall be of pressure type, downflow design, using automatic or manual regeneration. A manual override shall be provided for all automatic controls. Note: The department recommends automatic regeneration for small municipal water systems.
(2) Treatment systems designed for the removal of acute contaminants may not include a bypass for the anion exchange units. When an anion exchange unit is bypassed, a totalizing meter and a proportioning or regulating device or flow regulating valves shall be installed on the bypass line.(3) The design capacity of the regeneration process shall be in accordance with the specifications of the resin manufacturer. For nitrate removal, the design capacity shall not exceed 10,000 grains per cubic foot when the resin is regenerated at 15 pounds of salt per cubic foot of resin.(4) A water system treating for acute contaminants shall use at least 2 anion exchange units. The treatment capacity of each unit shall be capable of producing the maximum day water demand at a level below the maximum contaminant level for the contaminant of concern.(5) The anion exchange resin shall have high selectivity for the contaminant of concern.(6) Flow rates through the anion exchange units shall be justified through pilot testing under s. NR 811.44 or by appropriate justification by the resin manufacturer.(7) The freeboard design of the anion exchange unit shall be based upon the specific gravity of the media and the direction of water flow.(8) The bottoms, strainer systems, and support for anion exchange materials shall conform to requirements for rapid rate gravity filters under s. NR 811.49 (1).(9) Brine storage tanks shall conform to all of the following requirements: (a) Each tank shall be designed to hold at least 1.5 times the volume of salt delivered to permit refill before the tank is completely empty. The volume of both salt and brine storage to be provided depends upon the size of the plant, the proximity and assuredness of the salt source, and the method of delivery.(b) Each tank shall be isolated from possible sources of contamination.(c) Each tank shall be properly covered and equipped with manholes having overlapping watertight covers to prevent entry of surface runoff, where applicable. If the brine tanks are located outside of the pumphouse, the access manways shall meet the design requirements under s. NR 811.64 (7) (a).(d) Each tank shall contain overflows and vents that are designed in accordance with s. NR 811.64 (4) and (8), when applicable.(e) The water for filling the tank shall be distributed over the entire surface of the tank by pipes at least 2 pipe diameters above the maximum liquid level in the tank or be protected from back-siphonage.(f) The underdrain collection system shall be covered with a screen or perforated plate to allow brine but not salt to pass through.(g) The brine discharge line shall have a sampling tap so that the concentration of brine may be determined. A suitable means for measuring the volume of brine used for regeneration shall be provided.(h) Pipes and contact materials shall be resistant to the aggressiveness of salt. Steel and concrete shall be coated with an ANSI/NSF standard 61 certified, non-leaching protective coating that is compatible with salt and brine. Note: A copy of ANSI/NSF standard 61 dated March 15, 2022 is available for inspection at the Legislative Reference Bureau and may be obtained for personal use from NSF International, https://www.nsf.org.
(i) Bagged salt and dry bulk salt storage shall be enclosed and separated from other operating areas to prevent damage to equipment.(10) Brine wastes shall meet the requirements under s. NR 811.854.(11) Smooth-end sampling taps shall be provided for control purposes. Taps shall be located on each raw water source, each treatment unit influent and each treatment unit effluent. Testing equipment shall be provided to adequately control the treatment process at all plants.(12) Water from ion exchange treatment plants shall be stabilized as required under s. NR 811.58 (4), except when the department determines that the treated water will be non-corrosive.(13) Prior to start-up of the equipment, the resin shall be regenerated with no less than 2 bed volumes of water containing sodium chloride, or other appropriate regenerant followed by an adequate rinse.(14) Appropriate test equipment for the target contaminant shall be provided to determine treatment effectiveness.Wis. Admin. Code Department of Natural Resources NR 811.575
Adopted by, CR 22-074: cr. Register January 2024 No. 817, eff. 2/1/2024