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 811.52 - Iron and manganese control

Universal Citation: WI Admin Code ยง NR 811.52

Current through August 26, 2024

Iron and manganese control refers solely to treatment processes designed specifically for this purpose. The treatment process used will depend upon the character of the raw water. The selection of treatment processes shall meet specific local conditions as determined by engineering investigations, including chemical analyses of representative samples of water to be treated. The department may require the operation of a pilot plant in accordance with s. NR 811.44 in order to gather all information pertinent to the design. Consideration shall be given to adjusting the pH of the raw water to optimize the chemical reaction. The following requirements for specified treatment processes shall be met:

(1) REMOVAL BY OXIDATION-DETENTION-FILTRATION OR OXIDATION-FILTRATION.

(a) Oxidation. Oxidation may be by aeration, as indicated in s. NR 811.45, or by chemical oxidation with chlorine, potassium permanganate, sodium permanganate, hydrous manganese oxides, ozone or chlorine dioxide.

(b) Detention or reaction.
1. A detention period of 0.5 to 3 hours, as determined by pilot studies, shall be provided following oxidation by aeration in order to insure that the oxidation reactions are as complete as possible. The detention period may be omitted or reduced where a pilot plant study indicates no need for detention or that a detention period less than 30 minutes will be adequate and department approval is obtained.

2. The detention basin shall be designed as a holding tank with sufficient baffling to prevent short circuits. Sludge collection equipment is not required. The floor shall be sloped to facilitate cleaning. Detention basins shall meet all potable water reservoir standards as required by subch. IX.

(c) Sedimentation. Sedimentation basins shall be provided when treating water with high iron or manganese content or both and a significant volume of oxidized material will be created or where chemical coagulation is used to reduce the load on the filters. Provisions for sludge removal shall be made. Sedimentation basins shall meet all potable water reservoir standards as required by subch. IX.

(d) Rapid rate pressure filters. Use of rapid rate pressure filters as well as gravity filters may be considered for iron and manganese removal. Rapid rate pressure filters for iron and manganese shall meet the requirements under s. NR 811.49.

(2) REMOVAL BY LIME PROCESSES. The removal of iron and manganese by lime processes shall meet the requirements in s. NR 811.57.

(3) REMOVAL BY MANGANESE GREENSAND TYPE FILTRATION. The removal of iron and manganese by greensand type filtration consisting of a continuous feed of potassium or sodium permanganate to the influent of a manganese greensand filter, is more applicable to the removal of iron plus manganese than to the removal of iron only because of economic considerations. As an alternate method, application of the potassium permanganate to the greensand on a "batch" basis may be installed when the department determines "batch" application is as effective as continuous feed. The following requirements apply:

(a) The permanganate shall be applied as far ahead of the filter as practical.

(b) Other oxidizing agents or processes, such as chlorination or aeration, may be used prior to the permanganate feed to reduce the cost of the chemical.

(c) The normal filtration rate shall be 3 gallons per minute per square foot.

(d) The normal backwash rate shall be 8 to 10 gallons per minute per square foot for manganese greensand media and 15 to 20 gallons per minute per square foot for manganese coated media. Lesser backwash rates may be used if justified to the department by filter vessel manufacturers or through pilot studies under s. NR 811.44.

(e) Air washing may be provided.

(f) Sampling faucets shall be provided prior to application of permanganate, immediately ahead of filtration and at the filter outlet.

(4) REMOVAL BY ION EXCHANGE. The removal of iron and manganese by ion exchange may not be used unless pilot plant studies have demonstrated that satisfactory removal efficiencies can be continuously provided. There may be no oxidation of the iron or manganese prior to the process.

(5) TESTING EQUIPMENT. Testing equipment shall be provided for all plants. The equipment shall have the capacity to accurately measure the iron content to a minimum of 0.1 mg/l and the manganese content to a minimum of 0.05 mg/l.

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