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 811.58 - Stabilization

Universal Citation: WI Admin Code ยง NR 811.58

Current through August 26, 2024

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:

(1) CARBON DIOXIDE ADDITION.

(a) Recarbonation chamber design shall provide:
1. A total detention time of 20 minutes or as approved by the department.

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:
a. A mixing compartment having a detention time of at least 3 minutes.

b. A reaction compartment.

(b) The design shall prevent carbon dioxide from entering the plant from the recarbonation and reaction chamber.

(c) Plants generating carbon dioxide from combustion shall have open top recarbonation tanks in order to dissipate carbon monoxide gas.

(d) Provisions shall be made for draining the recarbonation basin and removing sludge.

(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:

(a) Feed equipment shall conform to requirements in ss. NR 811.38 to 811.40.

(b) Phosphate chemicals shall meet the NSF/ANSI Standard 60 requirements.

(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.

(d) Facilities shall be designed to maintain satisfactory chlorine residuals as indicated in s. NR 810.09 (2) and (3).

(e) The total phosphate applied may not exceed 10 mg/1 as PO 4.

(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.

(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.

(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.

(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.

(7) CONTROL. Laboratory equipment shall be provided for determining the effectiveness of stabilization treatment.

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