Wisconsin Administrative Code › Department of Natural Resources › NR 800 - Environmental Protection - Water Supply › Chapter NR 811 - Requirements For The Operation And Design Of Community Water Systems › Subchapter VII - Treatment › Section NR 811.575 - Anion exchange

Current through June 24, 2024
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.