Chapter NR 811

NR 811.45(3m)(d)2. 2. The air inlet shall be in a location protected from airborne contaminants.

NR 811.45(3m)(d)3. 3. An air flow meter or an alternative method to determine air flow shall be provided on the influent air line.

NR 811.45(3m)(d)4. 4. A positive air flow sensing device and a pressure gauge shall be installed on the air influent line. The positive air flow sensing device shall be a part of an automatic control system that will turn off the influent water if positive air flow is not detected. The pressure gauge shall serve as an indicator of the fouling buildup. The backup motor for the air blower shall be readily available.

NR 811.45(3m)(e) (e) Other design features shall meet all of the following requirements:

NR 811.45(3m)(e)1. 1. Include 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 811.45(3m)(e)2. 2. Include a method of cleaning the packing material when fouling may occur.

NR 811.45(3m)(e)3. 3. Tower effluent collection and pumping wells shall be constructed to potable reservoir construction standards as required under subch. IX.

NR 811.45(3m)(e)4. 4. Include provisions for extending the tower height without major reconstruction.

NR 811.45(3m)(e)5. 5. Include disinfection application points both ahead of and after the tower to control biological growth.

NR 811.45(3m)(e)6. 6. Include disinfection and adequate contact time after the water has passed through the tower, prior to the distribution system.

NR 811.45(3m)(e)7. 7. Include adequate packing support to allow free flow of water and prevent deformation with deep packing heights.

NR 811.45(3m)(e)8. 8. Include adequate foundation to support the tower and lateral support to prevent overturning to wind loading.

NR 811.45(3m)(e)9. 9. Include protections to prevent vandalism to the tower.

NR 811.45(3m)(e)10. 10. Provide access of all components of the tower, including the exhaust port and demister.

NR 811.45(3m)(e)11. 11. The operation of the blower and chemical feed pump shall be interlocked with the operation of the appropriate well or service pump.

NR 811.45(4) (4) Other methods of aeration. Other methods of aeration may be approved by the department only if a pilot plant study conducted in accordance with s. NR 811.44 demonstrates the method’s effectiveness. Methods include spraying, diffused air, and mechanical aeration. The treatment processes shall be designed to meet the particular needs of the water to be treated.

NR 811.45(5) (5) Disinfection. Aerated water other than from pressure aeration shall receive continuous disinfection treatment. A corporation stop shall be provided on the inlet piping to all non-pressure aerators to allow disinfection for emergency or maintenance purposes.

NR 811.45(6) (6) Protection from wind. Aerators that discharge through the atmosphere shall be protected by being placed in a louvered enclosure designed to provide easy access to the interior.

NR 811.45(7) (7) Protection from contamination. Aerators that are used for oxidation or removal of dissolved gases from waters that will be given no further treatment other than chlorination shall be protected from contamination from insects and birds, obnoxious fumes, all types of precipitation and condensation, and windborne debris or dust.

NR 811.45(8) (8) Bypass piping. Bypass piping and any associated valves or other appurtenances shall be installed to allow water to be bypassed around a non-pressure aerator unless the aerator is necessary to comply with primary maximum contaminant levels or the requirement is waived by the department because the water system has access to other water sources that can provide at least an average day supply of water.

NR 811.45(9) (9) Redundancy. Redundant aeration systems shall be provided for units installed to comply with primary maximum contaminant levels unless the requirement is waived by the department because the water system has access to other water sources that can provide at least an average day supply of water.

NR 811.45(10) (10) Water quality. A metal smooth-end sampling faucet installed on the aerator outlet piping and test equipment shall be provided to test for appropriate water quality parameters following aeration such as dissolved oxygen, pH, iron, manganese, radon gas, and carbon dioxide when required by the department to insure proper operation of the aeration equipment.

NR 811.45 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (1) (e), r. and recr. (2) (k), cr. (3m) Register January 2024 No. 817, eff. 2-1-24.

NR 811.46 NR 811.46 Arsenic removal. The following minimum requirements shall be met when the following treatment methods are employed for arsenic removal:

NR 811.46(1) (1) Pilot testing. All process designs shall be based on information from a pilot study unless waived by the department based upon previous demonstration that the process design will effectively remove arsenic based upon the water quality to be treated. Documentation shall be submitted to the department to support any pilot test waiver.

NR 811.46(2) (2) Oxidation and filtration. Arsenic III shall be oxidized by chemical or physical processes or both to arsenic V and then filtered out.

NR 811.46(2)(a) (a) Adequate detention time shall be provided if necessary to complete the conversion to arsenic V before filtration.

NR 811.46(2)(b) (b) Ferric chloride or ferric sulfate shall be added to the water supply for water with less than a 20 to 1 ratio of iron to arsenic if necessary in order to provide adequate arsenic removal efficiency.

NR 811.46(3) (3) Adsorptive media. Metal oxide coated adsorptive media may be used as the sole means of removing arsenic or in cooperation with or as a polishing unit after oxidation and filtration of arsenic.

NR 811.46(3)(a) (a) The adsorptive media shall be NSF/ANSI Standard 61 approved in accordance with s. NR 810.09 (5).

NR 811.46(3)(b) (b) The pilot study and final design shall address the following issues:

NR 811.46(3)(b)1. 1. Pre- and post-filtration adjustment of pH to enhance the arsenic removal rate and reduce water corrosivity.

NR 811.46(3)(b)2. 2. Conversion of the arsenic III to arsenic V prior to filtration.

NR 811.46(3)(b)3. 3. Oxidation and filtration of iron and manganese to prevent fouling of the media.

NR 811.46(3)(b)4. 4. Concentrations of sulfate and dissolved solids in the source water and the need to remove or reduce the concentrations in order to maintain treatment efficiency and minimize media fouling.

NR 811.46(4) (4) Other acceptable treatment methods. Coagulation and filtration, anion exchange, electrodialysis, membrane filtration, and lime softening are treatment methods that may also be used to remove arsenic. The pilot study and final design shall address the following issues, if applicable:

NR 811.46(4)(a) (a) Pre- and post-treatment adjustment of pH to enhance the arsenic removal rate, prevent scaling, or fouling of the treatment equipment, and reduce water corrosivity.

NR 811.46(4)(b) (b) Conversion of the arsenic III to arsenic V prior to removal.

NR 811.46(4)(c) (c) Oxidation and filtration of iron and manganese to prevent fouling of the treatment equipment.

NR 811.46(4)(d) (d) The use of ferric chloride, ferric sulfate, alum, or a polymer as coagulant aids.

NR 811.46(4)(e) (e) Concentrations of sulfate and dissolved solids in the source water and the need to remove or reduce the concentrations in order to maintain treatment efficiency and minimize treatment equipment fouling.

NR 811.46 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.

NR 811.47 NR 811.47 Clarification. Clarification plants prior to filtration shall meet all of the following requirements unless other design criteria are justified through pilot testing under s. NR 811.44 or other specific information provided to the department supports the proposed design, as determined by the department:

NR 811.47(1) (1) Provide a minimum of 2 units each for rapid mix, flocculation and sedimentation.

NR 811.47(2) (2) Permit operation of the units either in series or parallel.

NR 811.47(3) (3) Be constructed to permit units to be taken out of service without disrupting operation with drains or pumps sized to allow dewatering in a reasonable period of time.

NR 811.47(4) (4) Provide multiple-stage treatment facilities if required by the department.

NR 811.47(5) (5) Be started manually following shutdown.

NR 811.47(6) (6) Minimize hydraulic head losses between units to allow future changes in processes without the need for repumping.

NR 811.47(7) (7) Meet the following specific requirements:

NR 811.47(7)(a) (a) Presedimentation. Waters containing high turbidity or having unusual treatment requirements may require pretreatment, usually sedimentation or detention either with or without the addition of coagulation chemicals.

NR 811.47(7)(a)1. 1. ‘Basin design.’ Presedimentation basins shall have the following:

NR 811.47(7)(a)1.a. a. Hopper bottoms or be equipped with continuous mechanical sludge removal apparatus, and provide arrangements for dewatering.

NR 811.47(7)(a)1.b. b. Cover or superstructure.

NR 811.47(7)(a)2. 2. ‘Inlet.’ Incoming water shall be dispersed across the full width of the line of travel as quickly as possible. Short circuiting shall be prevented.

NR 811.47(7)(a)3. 3. ‘Bypass.’ Provisions for bypassing presedimentation basins shall be included.

NR 811.47(7)(a)4. 4. ‘Detention time.’ Three hours detention is the minimum period required for presedimentation. Greater detention may be required in individual cases of chemical pretreatment.

NR 811.47(7)(a)5. 5. ‘Raw water samples.’ A means for collecting raw water samples prior to any chemical addition shall be provided.

NR 811.47(7)(b) (b) Rapid mix. Mixing shall mean the rapid dispersion of chemicals throughout the water to be treated, usually by violent agitation. For surface water plants using direct or conventional filtration, the use of a primary coagulant is required at all times.

NR 811.47(7)(b)1. 1. ‘Mixing.’ The detention period shall not be more than 30 seconds with mixing equipment capable of imparting a minimum velocity gradient (G) of at least 750 feet per second per foot or as determined through jar testing. The appropriate G value and detention time shall be determined through jar testing.

NR 811.47(7)(b)2. 2. ‘Equipment.’ Basins shall be equipped with mechanical mixing devices unless other methods, such as baffling, or injection of chemicals at a point of high velocity, are approved by the department after determining that the other requirements of this chapter will be met. Variable speed drive equipment is recommended.

NR 811.47(7)(b)3. 3. ‘Location.’ The rapid mix and flocculation basin shall be as close together as possible.

NR 811.47(7)(c) (c) Flocculation — slow mixing. Flocculation installations shall meet all of the following requirements:

NR 811.47(7)(c)1. 1. ‘Basin design.’ Inlet and outlet design shall prevent short circuiting and destruction of floc. Series compartments shall be provided to minimize short-circuiting and to provide decreasing mixing energy with time. Basins shall be designed so that individual basins may be isolated without disrupting plant operation. A drain or pumps or both shall be provided to allow dewatering and sludge removal.

NR 811.47(7)(c)2. 2. ‘Detention.’ Flow-through velocity may be not less than 0.5 nor greater than 1.5 feet per minute with a detention time for floc formation of at least 30 minutes. Tapered energy with diminishing velocity gradient shall be considered in the design of the flocculation basin.

NR 811.47(7)(c)3. 3. ‘Equipment.’ Agitators shall be driven by variable speed drives or other means which vary the peripheral speed of paddles in the range of 0.5 to 3.0 feet per second and the tip speed of vertical shaft impellors in the range of 6 to 10 feet per second. Uniform mixing shall be provided to prevent settling in the flocculation basin.

NR 811.47(7)(c)4. 4. ‘Piping.’ Flocculation and sedimentation basins shall be as close together as possible. The velocity of flocculated water through pipes or conduits to settling basins may not be less than 0.5 nor greater than 1.5 feet per second. Allowances shall be made to minimize turbulence at bends and changes in direction.

NR 811.47(7)(c)5. 5. ‘Other designs.’ Baffling may be used to provide flocculation only after approval by the department. The design shall be such that the velocities and flows in this section shall be maintained.

NR 811.47(7)(c)6. 6. ‘Superstructure.’ A superstructure shall be provided over the flocculation basins.

NR 811.47(7)(d) (d) Sedimentation. Sedimentation shall follow flocculation. The detention time for effective clarification is dependent upon factors related to basin design as well as the nature of the raw water, such as turbidity, color and colloidal matter, and taste and odor causing compounds.

NR 811.47(7)(d)1. 1. ‘Detention time.’ Plants with conventional sedimentation shall provide a minimum of 4 hours of settling time. This may be reduced to 2 hours for lime-soda softening facilities treating only groundwater. Also, reduced sedimentation time may be approved when equivalent effective settling is demonstrated or when overflow rate is not more than 0.5 gallons per minute per square foot.

NR 811.47(7)(d)2. 2. ‘Inlet devices.’ Inlets shall be designed to distribute the water equally and at uniform velocities. Open ports, submerged ports, and similar entrance arrangements are required. A baffle shall be constructed across the basin, close to the inlet end, and project several feet below the water surface to dissipate inlet velocities and provide uniform flows across the basin.

NR 811.47(7)(d)3. 3. ‘Outlet devices.’ Outlet devices shall be designed to maintain velocities suitable for settling in the basin and to minimize short circuiting. The use of submerged orifices is recommended in order to provide volume above the orifices for storage when there are fluctuations in flow.

NR 811.47(7)(d)4. 4. ‘Weir overflow rate.’ The rate of flow over the outlet weir may not exceed 20,000 gallons per day per foot of weir length. If submerged ports or orifices are used as an alternate for overflow weirs, they may not be lower than 3 feet below the flow line with flow rates equivalent to weir loadings. The entrance velocity through the submerged orifices shall not exceed 0.5 feet per second.

NR 811.47(7)(d)5. 5. ‘Drainage.’ Basins shall be provided with a means for dewatering. Basin bottoms shall slope toward the drain not less than one foot in 12 feet where mechanical sludge collection is not provided.

NR 811.47(7)(d)6. 6. ‘Covers.’ Covers or superstructures are required at all plants. Where covers are used, access hatches shall be provided as well as drop light connections so that observation of the floc can take place at the inlet, midpoint and outlet of the basin.

NR 811.47(7)(d)7. 7. ‘Velocity.’ The velocity through settling basins may not exceed 0.5 feet per minute. The basins shall be designed to minimize short circuiting. Fixed or adjustable baffles shall be provided as necessary to achieve the maximum potential for clarification.

NR 811.47(7)(d)8. 8. ‘Overflow.’ An overflow weir or pipe shall be installed, which will establish the maximum water level desired on top of the filters. It shall discharge by gravity with a downturned pipe elbow a minimum of one foot above a concrete splash pad and shall be covered with 4-mesh corrosion resistant screen at a location where the discharge is visible and where the water can be appropriately drained.

NR 811.47(7)(d)9. 9. ‘Safety.’ Guard rails shall be installed around openings which may be hazardous to maintenance personnel. Permanent holders or handholds shall be provided on the inside walls of basins above the water level.

NR 811.47(7)(d)10. 10. ‘Sludge collection.’ Mechanical sludge collection equipment may be provided.

NR 811.47(7)(d)11. 11. ‘Sludge removal.’ Facilities for disposal of sludge are required by the department. Sludge removal design shall provide:

NR 811.47(7)(d)11.a. a. Sludge pipes not less than 3 inches in diameter and so arranged as to facilitate cleaning.

NR 811.47(7)(d)11.b. b. Entrance to sludge withdrawal piping to prevent clogging.

NR 811.47(7)(d)11.c. c. Valves located outside the tank for accessibility.

NR 811.47(7)(d)11.d. d. Provisions for the operator to observe and sample sludge being withdrawn from the unit.

NR 811.47(7)(d)12. 12. ‘Sludge disposal.’ Sections NR 811.858 and 811.861 contain additional specific requirements for sludge disposal. Flushing lines or hydrants shall be provided to backflush sludge lines and basins or for other purposes. Protection shall be provided for all potable water lines used if potable water could become contaminated by nonpotable water.

NR 811.47(7)(e) (e) Solids contact unit. Units designed for combined softening and clarification, if water characteristics, especially temperature, do not fluctuate rapidly and flow rates are uniform and operation is continuous, may be used if specifically approved by the department. Units shall be designed for the maximum uniform rate and be adjustable to changes in flow, which are less than the design rate and for changes in water characteristics. A minimum of 2 units are required unless the department waives this requirement. For plants with multiple units, the rated capacity of the plant shall be available with one unit out of service.

NR 811.47(7)(e)1. 1. ‘Installation of equipment.’ Supervision by a representative of the manufacturer shall be provided whenever mechanical equipment is installed and at the time of initial operation.

NR 811.47(7)(e)2. 2. ‘Operating equipment.’ A complete outfit of tools and accessories shall be provided. Laboratory equipment to control the treatment process shall be provided at all waterworks. In addition, sampling taps with adequate piping located to permit the collection of samples of water from critical portions of the units shall be provided.