NR 811.56(2)(f)
(f) Sodium silicate may not be applied ahead of iron or manganese removal treatment.
NR 811.57
NR 811.57 Softening. The softening process selected shall be based upon the chemical qualities of the raw water, the desired finished water quality, the requirements for disposal of sludge or brine waste, the cost of plant and chemicals, and plant location. The applicability of the process chosen shall be demonstrated and discussed in detail in an engineering report. For very hard water, the sodium levels in cation exchange softened water shall be considered in selecting the treatment process. Following are requirements for specific processes:
NR 811.57(1)
(1)
Lime-soda process. The applicable design standards for lime-soda softening of groundwater are the same as those for conventional clarification-filtration surface water treatment plants, except that the minimum settling time may be reduced to 2 hours. Where softening is included in the surface water treatment process, the clarification criteria shall govern. In addition:
NR 811.57 Note
Note: See s.
NR 811.47 for criteria pertaining to softening with solids contact units and s.
NR 811.49 for filtration requirements.
NR 811.57(1)(a)
(a) Mechanical sludge removal equipment shall be provided in the sedimentation basin.
NR 811.57(1)(b)
(b) Determinations shall be made for the carbon dioxide content of the raw water.
NR 811.57 Note
Note: When concentrations exceed 10 mg/l, the economics of removal by aeration as opposed to removal with lime should be considered. See s.
NR 811.45 for aeration requirements.
NR 811.57(1)(c)
(c) Equipment for stabilization of water softened by the lime-soda process is required.
NR 811.57 Note
Note: See s.
NR 811.58 for stabilization requirements.
NR 811.57(1)(d)
(d) Provisions shall be included for proper disposal of softening sludges.
NR 811.57 Note
Note: See s.
NR 811.858 for design requirements.
NR 811.57(1)(e)
(e) The use of excess lime may not be substituted for chlorination or any other approved method of disinfection.
NR 811.57(2)
(2)
Cation exchange process. Iron, manganese or a combination of both in the oxidized state or unoxidized state may cause resin fouling in the ion exchange process. Pretreatment shall be required whenever the content of iron, manganese, or a combination of both is one milligram per liter or more. In specific instances, the department may also require pretreatment when lesser amounts exist. All of the following requirements shall be satisfied unless the department determines sufficient justification for alternative operational parameters is provided by the vessel manufacturer or demonstrated through pilot testing under s.
NR 811.44:
NR 811.57(2)(a)
(a) The units shall be of pressure or gravity type, of either an upflow or downflow design, using automatic or manual regeneration. Automatic regeneration is suggested for small plants. A manual override shall be provided for all automatic controls.
NR 811.57(2)(b)
(b) The design capacity for hardness removal may not exceed 20,000 grains per cubic foot when resin is regenerated with 0.3 pounds of salt per kilograin of hardness removed.
NR 811.57(2)(c)
(c) The depth of the exchange material may not be less than 3 feet.
NR 811.57(2)(d)
(d) The rate of softening may not exceed 7 gallons per square foot per minute, and the backwash rate shall be 6 to 8 gallons per square foot per minute.
NR 811.57(2)(e)
(e) The freeboard design shall be based upon the specific gravity of the media and the direction of water flow.
NR 811.57(2)(f)
(f) The bottoms, strainer systems, and support for the exchange materials shall conform to criteria provided for rapid rate gravity filters in s.
NR 811.49.
NR 811.57(2)(g)
(g) Facilities shall be included for even distribution of the brine over the entire surface of both upflow or downflow units. Backwash, rinse, and air relief discharge pipes shall be installed in such a manner as to prevent back-siphonage.
NR 811.57(2)(h)
(h) A bypass shall be provided around softening units to produce a blended water of desirable hardness. Meters shall be installed on the bypass line and on each softener unit. An automatic proportioning or regulating device and shut-off valve shall be provided on the bypass line. The department may require treatment of the bypassed water to obtain acceptable levels of iron or manganese in the finished water.
NR 811.57(2)(i)
(i) Waters having 5 units or more of turbidity may not be applied directly to the cation exchange softener. Silica gel materials may not be used for waters having a pH above 8.4 or when iron is present. When the applied water contains a chlorine residual, the cation exchange material shall be a type that is not damaged by residual chlorine. Phenolic resin may not be used.
NR 811.57(2)(j)
(j) Brine storage tanks shall conform to the following requirements:
NR 811.57(2)(j)1.
1. The wet storage 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.
NR 811.57(2)(j)3.
3. It shall be properly covered and equipped with manholes having overlapping watertight covers to prevent entry of surface runoff where applicable.
NR 811.57(2)(j)5.
5. 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.
NR 811.57(2)(j)6.
6. The underdrain collection system shall be covered with a screen or perforated plate to allow brine but not salt to pass through.
NR 811.57(2)(j)7.
7. A sampling tap shall be provided on the brine discharge line in order that the concentration of brine can be determined. A suitable means for measuring the volume of brine used for regeneration shall be provided.
NR 811.57(2)(j)8.
8. Pipes and contact materials shall be resistant to the aggressiveness of salt. Steel and concrete shall be coated with a non-leaching protective coating that is compatible with salt and brine and is certified by ANSI/NSF standard 61, dated March 15, 2022, which is incorporated by reference.
NR 811.57 Note
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.
NR 811.57(2)(j)9.
9. Bagged salt and dry bulk salt storage shall be enclosed and separated from other operating areas to prevent damage to equipment.
NR 811.57(2)(L)
(L) 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.
NR 811.57(2)(m)
(m) Water from ion exchange treatment plants shall be stabilized as required in s.
NR 811.58 (4), except where it can be shown that the treated water will be non-corrosive.
NR 811.57 History
History: CR 09-073: cr.
Register November 2010 No. 659, eff. 12-1-10;
CR 22-074: am. (2) (intro.), (j) 3., 4., cr. (2) (j) 8., 9. Register January 2024 No. 817, eff. 2-1-24.
NR 811.575
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:
NR 811.575(1)
(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.
NR 811.575 Note
Note: The department recommends automatic regeneration for small municipal water systems.
NR 811.575(2)
(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.
NR 811.575(3)
(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.
NR 811.575(4)
(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.
NR 811.575(5)
(5) The anion exchange resin shall have high selectivity for the contaminant of concern.
NR 811.575(6)
(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.
NR 811.575(7)
(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.
NR 811.575(8)
(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).
NR 811.575(9)
(9) Brine storage tanks shall conform to all of the following requirements:
NR 811.575(9)(a)
(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.
NR 811.575(9)(b)
(b) Each tank shall be isolated from possible sources of contamination.
NR 811.575(9)(c)
(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).
NR 811.575(9)(e)
(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.
NR 811.575(9)(f)
(f) The underdrain collection system shall be covered with a screen or perforated plate to allow brine but not salt to pass through.
NR 811.575(9)(g)
(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.
NR 811.575(9)(h)
(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.
NR 811.575 Note
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.
NR 811.575(9)(i)
(i) Bagged salt and dry bulk salt storage shall be enclosed and separated from other operating areas to prevent damage to equipment.
NR 811.575(11)
(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.
NR 811.575(12)
(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.
NR 811.575(13)
(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.
NR 811.575(14)
(14) Appropriate test equipment for the target contaminant shall be provided to determine treatment effectiveness.
NR 811.575 History
History: CR 22-074: cr. Register January 2024 No. 817, eff. 2-1-24. NR 811.58
NR 811.58 Stabilization. Water that is unstable to the extent of causing corrosion or deposition problems in the distribution system, whether a result of natural causes or water treatment processes, shall be stabilized. The following standards shall apply:
NR 811.58(1)(a)1.
1. A total detention time of 20 minutes or as approved by the department.
NR 811.58(1)(a)2.
2. Two compartments, with a depth that will provide a diffuser submergence not less than 7.5 feet nor greater than recommended by the manufacturer and as follows:
NR 811.58(1)(b)
(b) The design shall prevent carbon dioxide from entering the plant from the recarbonation and reaction chamber.
NR 811.58(1)(c)
(c) Plants generating carbon dioxide from combustion shall have open top recarbonation tanks in order to dissipate carbon monoxide gas.
NR 811.58(1)(d)
(d) Provisions shall be made for draining the recarbonation basin and removing sludge.
NR 811.58(2)
(2)
Phosphates. Phosphates may be used for sequestering calcium in lime softened water, corrosion control and in conjunction with alkali feed following ion exchange softening. When used:
NR 811.58(2)(b)
(b) Phosphate chemicals shall meet the NSF/ANSI Standard 60 requirements.
NR 811.58(2)(c)
(c) Stock phosphate solution shall be kept covered and disinfected by carrying an approximate 10 mg/1 chlorine residual. The department may exempt phosphate solutions having a pH of 2.0 or less from this requirement.
NR 811.58(2)(e)
(e) The total phosphate applied may not exceed 10 mg/1 as PO
4.
NR 811.58(3)
(3)
Split treatment. If approved by the department, a lime-soda water treatment plant may be designed using `split treatment' in which raw water is blended with lime-treated water to partially stabilize the water. Treatment plants designed to utilize `split treatment' shall contain facilities for further stabilization by other methods.
NR 811.58(4)
(4)
Alkali feed. An alkali feeder shall be provided for all ion exchange water softening plants to provide stable water unless the effluent water is shown to be non-corrosive. Other waters may also be corrosive and require pH adjustment. The chemical shall be adequately mixed and the point of application located such that any deposition in the piping is minimized. The piping shall be accessible for cleaning or replacement. Equipment for monitoring pH shall be provided.
NR 811.58(5)
(5)
Carbon dioxide reduction by aeration. The carbon dioxide content of an aggressive water may be reduced by aeration. Aeration devices shall conform to s.
NR 811.45.
NR 811.58(6)
(6)
Other treatment. Other treatment for controlling corrosive waters by the use of sodium silicate and sodium bicarbonate may be used where necessary. Any proprietary compound shall receive the specific approval of the department before use. Chemical feeders shall comply with the requirements in subch.
VI.
NR 811.58(7)
(7)
Control. Laboratory equipment shall be provided for determining the effectiveness of stabilization treatment.
