Section 811.52. Iron and manganese control.

  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. Use, however, is subject to the following conditions:

1. Minimum criteria relative to number, rate of filtration, structural details and hydraulics, filter media, etc., provided for rapid rate gravity filters in s. NR 811.49 also apply to pressure filters, where appropriate.

2. Generally, the design filtration rate shall be 3 gallons per minute per square foot of filter area. Higher or lower rates may be justified based on in-plant or pilot plant studies.

3. Filter design shall provide for:

a. Loss of head gauges with a suitable range in head on the inlet and outlet pipes of each filter.

b. An easily readable meter or flow indicator on each battery of filters.

c. Piping and shut-off valves so that each filter can be operated and backwashed individually.

d. Minimum side wall shell height of 5 feet. A corresponding reduction in side wall height may be approved where proprietary bottoms permit reduction of the gravel depth.

e. Wastewater collection a minimum of 18 inches above the surface of the media.

f. An underdrain system to efficiently collect the filtered water and distribute the backwash water.

g. Backwash and air relief valve discharge piping terminating with a free air break a minimum of 24 inches above the floor or wastewater collection pipe or sump.

h. Inlet and outlet sampling faucets for each filter.

(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.

(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.

History: CR 09-073 : cr. Register November 2010 No. 659 , eff. 12-1-10.

Note

A flow indicator is recommended for each filtering unit. Microsoft Windows NT 6.1.7601 Service Pack 1