Chapter NR 811

NR 811.52(1) (1) Removal by oxidation-detention-filtration or oxidation-filtration.

NR 811.52(1)(a) (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.

NR 811.52(1)(b) (b) Detention or reaction.

NR 811.52(1)(b)1. 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.

NR 811.52(1)(b)2. 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.

NR 811.52(1)(c) (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.

NR 811.52(1)(d) (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.

NR 811.52(2) (2) Removal by lime processes. The removal of iron and manganese by lime processes shall meet the requirements in s. NR 811.57.

NR 811.52(3) (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:

NR 811.52(3)(a) (a) The permanganate shall be applied as far ahead of the filter as practical.

NR 811.52(3)(b) (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.

NR 811.52(3)(c) (c) The normal filtration rate shall be 3 gallons per minute per square foot.

NR 811.52(3)(d) (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.

NR 811.52(3)(e) (e) Air washing may be provided.

NR 811.52(3)(f) (f) Sampling faucets shall be provided prior to application of permanganate, immediately ahead of filtration and at the filter outlet.

NR 811.52(4) (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.

NR 811.52(5) (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.

NR 811.52 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: renum. (1) (d) (intro.) to (1) (d) and am., r. (1) (d) 1. to 3., am. (3) (d) Register January 2024 No. 817, eff. 2-1-24.

NR 811.53 NR 811.53 Organics removal.

NR 811.53(1) (1) General requirements. Organic compounds may be removed by a variety of processes. All process designs shall be based on information from a pilot study conducted in accordance with s. NR 811.44 with the compounds to be removed unless the pilot study is waived by the department. Unless the department approves other requirements, the processes shall be designed to remove a minimum of 99% of the contaminant in question.

NR 811.53(2) (2) Packed tower aeration. Packed tower aeration units shall meet the following requirements:

NR 811.53(2)(a) (a) General. Packed tower aeration, which is also known as air stripping, may be used for the removal of volatile organic chemicals, trihalomethanes, carbon dioxide, and radon.

NR 811.53(2)(b) (b) Process design. The process design shall include determination of the Henry’s Constant for each contaminant, the mass transfer coefficient, air pressure drop, and stripping factor. Justification shall be provided for the selected design parameters including the height and other dimensions of the unit, air to water ratio, packing specifications, packing depth, and surface loading rate.

NR 811.53(2)(b)1. 1. Pilot testing considerations:

NR 811.53(2)(b)1.a. a. The pilot study shall evaluate a variety of loading rates and air to water ratios at the peak contaminant concentration. Special consideration shall be given to removal efficiencies when multiple contaminants occur.

NR 811.53(2)(b)1.b. b. If there is adequate past performance data on the contaminant to be treated, including at the peak contaminant concentration, the department may approve the process design based on the appropriate calculations without pilot testing.

NR 811.53(2)(b)2. 2. The installation shall be designed to reduce contaminants to below the maximum contaminant level and to the lowest practical level.

NR 811.53(2)(b)3. 3. The packing material shall be NSF/ANSI Standard 61 approved for use in potable water in accordance with s. NR 810.09 (5). The packing material shall be resistant to the aggressiveness of the water, dissolved gasses, any chemicals added to the water supply, and any cleaning materials.

NR 811.53(2)(b)4. 4. The packing tower shall be constructed of materials compatible with potable water including stainless steel, reinforced concrete, aluminum, reinforced fiberglass, or plastic. The tower construction materials shall be resistant to the aggressiveness of the water, dissolved gasses, any chemicals added to the water supply, and any cleaning materials. Towers constructed of light weight materials shall be provided with adequate support to prevent damage from wind.

NR 811.53(2)(b)5. 5. The ratio of the column diameter to the packing diameter shall be at least 7:1 for the pilot unit and at least 10:1 for the full scale tower. The type and size of the packing used in the full scale unit shall be the same as that used in the pilot unit.

NR 811.53(2)(b)6. 6. The blower shall be adequately sized to provide sufficient air to achieve the desired removal rates. The minimum volumetric air to water ratio at the maximum water flow rate shall be 25:1. The maximum air to water ratio shall not exceed 80:1.

NR 811.53(2)(b)7. 7. The design shall give consideration to potential fouling problems from calcium carbonate, iron and manganese precipitation, and from bacterial growth. Pretreatment shall be provided where necessary to prevent significant fouling. Disinfection capability shall be provided immediately before and after packed tower aeration.

NR 811.53(2)(b)8. 8. The effects of temperature shall be considered in the process design as a drop in water temperature can result in a drop in contaminant removal efficiency.

NR 811.53(2)(c) (c) Water flow system.

NR 811.53(2)(c)1. 1. Water shall be distributed uniformly at the top of the tower using spray nozzles or orifice-type distributor trays that prevent short circuiting. For multi-point injection, a minimum of one injection point for every 30 square inches of tower cross-sectional area shall be installed.

NR 811.53(2)(c)2. 2. A mist eliminator shall be provided above the water distributor system.

NR 811.53(2)(c)3. 3. A side wiper redistribution ring shall be provided at least every 10 feet in order to prevent water channeling along the tower wall and short circuiting.

NR 811.53(2)(c)4. 4. Sample faucets shall be provided on the tower inlet and outlet piping.

NR 811.53(2)(c)5. 5. An outlet sump, if provided, shall be accessible for cleaning purposes and be equipped with a drain valve. The drain shall not be directly connected to a storm or sanitary sewer.

NR 811.53(2)(c)6. 6. A drain fitting shall be installed in the outlet piping to allow for the discharge of water and any chemicals used to clean the tower. The drain shall not be directly connected to a storm or sanitary sewer.

NR 811.53(2)(c)7. 7. The design shall prevent freezing of the inlet riser, tower, and the outlet piping when the unit is not operating.

NR 811.53(2)(c)8. 8. All buried piping shall be maintained under a positive pressure greater than the elevation of the ground surface.

NR 811.53(2)(c)9. 9. The water flow to each tower shall be metered.

NR 811.53(2)(c)10. 10. Consideration shall be given to installing a butterfly valve in the inlet piping to control the water flow rate and to minimize air entrainment.

NR 811.53(2)(c)11. 11. A means shall be provided to prevent flooding of the air blower.

NR 811.53(2)(c)12. 12. The inlet piping shall be supported separately from the tower’s main structural support.

NR 811.53(2)(d) (d) Air flow system.

NR 811.53(2)(d)1. 1. The air inlet shall be installed in a protected location.

NR 811.53(2)(d)2. 2. The air inlet to the blower and the tower discharge vent shall be screened and provided with a downturned, hooded or mushroom cap that protects the screen from the entrance of extraneous matter including insects and birds, obnoxious fumes, all types of precipitation and condensation, and windborne debris or dust. The screens shall be constructed of 24-mesh corrosion resistant material and installed at a location least susceptible to vandalism or damage. The air inlet shall also be provided with a dust filter.

NR 811.53 Note Note: It is recommended that a 4-mesh corrosion resistant screen be installed in front of the 24-mesh screen on the air inlet system.

NR 811.53(2)(d)3. 3. The blower shall be provided with a weather-proof motor, a tight housing, and an adequate foundation.

NR 811.53(2)(d)4. 4. An air flow meter or department approved alternative method for determining the air flow shall be installed on the air inlet piping.

NR 811.53(2)(d)5. 5. A positive air flow sensing device and a pressure gauge shall be installed on the air inlet line to the tower. If positive air flow is not detected, the device shall automatically shut down the water flow.

NR 811.53(2)(d)6. 6. A backup motor for the blower shall be readily available where the tower is used to maintain primary drinking water standards.

NR 811.53(2)(e) (e) Other requirements.

NR 811.53(2)(e)1. 1. The tower shall be provided with a sufficient number of access ports with a minimum diameter of 24 inches to facilitate inspection, media replacement, media cleaning, and maintenance of the interior.

NR 811.53(2)(e)2. 2. A means shall be provided for cleaning the packing material should it become fouled.

NR 811.53(2)(e)3. 3. Any clearwell or reservoir constructed to receive water from a tower shall be constructed to meet the potable water reservoir requirements of s. NR 811.64.

NR 811.53(2)(e)4. 4. The tower shall be designed and constructed so that it can be extended without major reconstruction.

NR 811.53(2)(e)5. 5. A means of bypassing the tower shall be provided unless the requirement is waived by the department because the water system has access to other water sources that can provide an average day supply of water at minimum.

NR 811.53(2)(e)6. 6. Disinfection application points shall be provided on the tower inlet and outlet piping.

NR 811.53(2)(e)7. 7. Any water passed through the tower shall be continuously disinfected. If raw water has bacteriological issues, the department may require a minimum of 4-log inactivation of viruses as determined by the department on a case-by-case basis.

NR 811.53(2)(e)8. 8. The water supply pump or pumps, blower motor, disinfection equipment, and the positive air flow sensing device shall be electrically interconnected to operate in series.

NR 811.53(2)(e)9. 9. Adequate packing support shall be provided to allow the free flow of water and to prevent packing deformation.

NR 811.53(2)(e)10. 10. Adequate auxiliary power shall be provided to operate the air blower and disinfection equipment during power failures unless the requirement is waived by the department because the water system has access to other water sources that can provide an average day supply of water at minimum or operation of the tower is not mandatory to meet primary drinking water standards.

NR 811.53(2)(e)11. 11. The tower shall be provided with an adequate foundation and lateral support to prevent overturning due to wind loading.

NR 811.53(2)(e)12. 12. The equipment shall be located within a secure building or within a locked security fence to prevent vandalism.

NR 811.53(2)(e)13. 13. An access ladder with safety cage shall be provided to allow access and inspection of all areas of the tower.

NR 811.53(2)(e)14. 14. Exhaust air shall be discharged directly to the outside atmosphere and in a location that will be protective of public health. Air emissions controls shall be provided if necessary to meet air quality standards.

NR 811.53(2)(e)15. 15. Noise control equipment shall be provided where systems are located in residential areas.

NR 811.53(3) (3) Granular activated carbon filters. Granular activated carbon filter installations shall meet the following requirements:

NR 811.53(3)(a) (a) The maximum filtration rate for pressure filters shall be 6 gallons per minute per square foot of filter area. The maximum filtration rate for gravity filters shall be 3 gallons per minute per square foot of filter area. Higher rates may be justified based on pilot studies for removal of the contaminant in question.

NR 811.53(3)(b) (b) The water from the carbon filter shall be continuously disinfected.

NR 811.53(3)(c) (c) The filter design shall provide for:

NR 811.53(3)(c)1. 1. Loss of head gauges on the inlet and outlet pipes of each filter.

NR 811.53(3)(c)2. 2. A meter or flow indicator.

NR 811.53(3)(c)3. 3. Adequate freeboard for backwashing based on the specific gravity of the media.

NR 811.53(3)(c)4. 4. An underdrain system to effectively collect the filtered water and distribute the backwash water.

NR 811.53(3)(c)5. 5. Backwash and air relief valves having discharges that terminate in a free air break at least 24 inches above the floor.

NR 811.53(3)(c)6. 6. Smooth-end sampling faucets on the inlet and outlet pipes of each filter.

NR 811.53(3)(c)7. 7. The ability to conveniently inspect, replace, or regenerate the media.

NR 811.53(3)(d) (d) The carbon used shall be virgin carbon.

NR 811.53(3)(e) (e) Information supporting selection of the carbon for removal of the contaminants in question shall be provided to the department.

NR 811.53(3)(f) (f) A plan for the disposal of the spent carbon shall be included in the specifications. Disposal of spent granular activated carbon shall comply with s. NR 811.859.

NR 811.53(3)(g) (g) An assessment of the impacts of radon and its decay products on operation, operator safety, and waste disposal shall be provided to the department.

NR 811.53 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (2) (e) 7. Register January 2024 No. 817, eff. 2-1-24.

NR 811.54 NR 811.54 Ozonation. Ozonation can be used for a variety of purposes including disinfection, oxidation, and microflocculation. When applied, all of these reactions may occur but typically only one is the primary purpose for its use. Ozonation can be used for the removal of color, taste and odors, organics, algae, cyanide, hydrogen sulfide, iron, manganese, and heavy metals. In addition to these treatment processes, ozone is an acceptable alternative to chlorine disinfectants. Given the sophisticated nature of the ozone process, consideration shall be given to the need for maintaining qualified operators to operate and maintain the equipment. The following requirements shall be met:

NR 811.54(1) (1) General. The following general requirements shall be met:

NR 811.54(1)(a) (a) All process designs shall be based on bench or pilot scale studies of dosage requirements, application points, and detention times conducted in accordance with s. NR 811.44.