Chapter NR 811

NR 811.47(7)(d)11.d. d. Provisions for the operator to observe and sample sludge being withdrawn from the unit.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

NR 811.47(7)(e)3. 3. ‘Chemical feed.’ Chemicals shall be applied at points and by means as to ensure satisfactory mixing of the chemicals with the water.

NR 811.47(7)(e)4. 4. ‘Mixing.’ Mixing devices employed shall be constructed to provide adequate mixing of the raw water with previously formed sludge particles and to prevent deposition of solids in the mixing zone. A rapid mix device or chamber ahead of the solids contact unit may be required by the department.

NR 811.47(7)(e)5. 5. ‘Flocculation.’ Flocculation equipment shall be adjustable by speed, or pitch or both, provide for coagulation to occur in a separate chamber or baffled zone within the unit, and provide a flocculation and mixing period of not less than 30 minutes.

NR 811.47(7)(e)6. 6. ‘Sludge concentrators.’ Sludge concentrators shall provide either internal or external concentrators in order to obtain a concentrated sludge with a minimum of wastewater.

NR 811.47(7)(e)7. 7. ‘Sludge removal.’ Sludge removal design shall provide all of the following:

NR 811.47(7)(e)7.a. a. Sludge pipes not less than 3 inches in diameter, arranged to facilitate cleaning.

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

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

NR 811.47(7)(e)7.d. d. Facilities for an operator to observe or sample sludge being withdrawn from the unit.

NR 811.47(7)(e)8. 8. ‘Cross-connections.’ Sludge blow-off outlets and drains shall terminate and discharge at places approved by the department. Cross-connection control shall be included for all potable water lines such as those used to backflush sludge lines or flush basins if potable water could become contaminated by nonpotable water.

NR 811.47(7)(e)9. 9. ‘Detention period.’ The detention time shall be established on the basis of the raw water characteristics and local conditions that affect the operation of the unit. Based on design flow rates, the minimum detention time shall be 2 to 4 hours for suspended solids contact clarifiers and softeners treating surface waters, and one to 2 hours for the suspended solids contact softeners treating only groundwater.

NR 811.47(7)(e)10. 10. ‘Suspended slurry concentrate.’ Softening units shall be designed so that continuous slurry concentrates of 1% or more, by weight, can be effectively maintained.

NR 811.47(7)(e)11. 11. ‘Water losses.’

NR 811.47(7)(e)11.a. a. Units shall be provided with suitable controls for sludge withdrawal.

NR 811.47(7)(e)11.b. b. Total water loss may not exceed 5% for clarifiers or 3% for softening units.

NR 811.47(7)(e)11.c. c. Solids concentration of sludge discharged to waste shall be at least 3% by weight for clarifiers and 5% by weight for softeners.

NR 811.47(7)(e)12. 12. ‘Weir or orifices.’ The units shall be equipped with either overflow weirs or orifices. Weirs shall be adjustable, at least equivalent in length to the perimeter of the tank, and constructed so that surface water does not travel over 10 feet horizontally to the collection trough.

NR 811.47(7)(e)13. 13. ‘Weir or orifice loading.’ Weir loading may not exceed 20 gallons per minute per foot of weir length for units used for softeners, or 10 gallons per minute per foot of weir length for units used for clarifiers. Where orifices are used, the loading rate per foot shall be equivalent to weir loadings. Orifices or weirs shall produce uniform rising rates over the entire area of the tank.

NR 811.47(7)(e)14. 14. ‘Upflow rates.’ Unless supporting data is submitted to the department and the department grants an exception, the following rates may not be exceeded:

NR 811.47(7)(e)14.a. a. 1.75 gallons per minute per square foot of area at the slurry separation line if units are used for softeners.

NR 811.47(7)(e)14.b. b. 1.0 gallon per minute per square foot of area at the sludge separation line if units are used for clarifiers.

NR 811.47(7)(f) (f) Tube or plate settlers. Proposals for settler unit clarification shall include pilot plant or a full scale demonstration or both satisfactory to the department prior to the preparation of final plans and specifications for approval. Settler units consisting of variously shaped tubes or plates which are installed in multiple layers and at an angle to the flow, may be used for sedimentation, following flocculation. Tube or plate settler installations shall meet the following:

NR 811.47(7)(f)1. 1. ‘Inlet and outlet considerations.’ Design the inlets and outlets to maintain velocities suitable for settling in the basin and to minimize short-circuiting.

NR 811.47(7)(f)2. 2. ‘Drainage.’ Drain piping from the settler units shall be sized to facilitate a quick flush of the settler units and to prevent flooding other portions of the plant.

NR 811.47(7)(f)3. 3. ‘Protection from freezing.’ Units shall be located within a plant or within a covered basin.

NR 811.47(7)(f)4. 4. ‘Application rate for tubes.’ A maximum application rate of 2 gallons per minute per square foot of cross-sectional area, unless higher rates are successfully shown through pilot plant or in-plant demonstration studies and are approved by the department.

NR 811.47(7)(f)5. 5. ‘Application rate for plates.’ A maximum plate loading rate of 0.5 gallons per minute per square foot, based on 80 percent of the projected horizontal plate area.

NR 811.47(7)(f)6. 6. ‘Flushing lines.’ Flushing lines shall be provided to facilitate maintenance and shall be properly protected against backflow or back siphonage.

NR 811.47(7)(f)7. 7. ‘Placement.’ Modules shall be placed in zones of stable hydraulic conditions and in areas nearest effluent launders for basins not completely covered by the modules.

NR 811.47(7)(f)8. 8. ‘Inlets and outlets.’ Inlets and outlets shall conform with par. (d) 2. and 3.

NR 811.47 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (intro.), (7) (b) 1. Register January 2024 No. 817, eff. 2-1-24.

NR 811.48 NR 811.48 Chlorination. Chlorine installations shall meet the following requirements:

NR 811.48(1) (1) Chlorination equipment.

NR 811.48(1)(a) (a) Type. The following types of chemical feed equipment may be used to feed chlorine:

NR 811.48(1)(a)1. 1. Solution-feed-gas-type chlorinators.

NR 811.48(1)(a)2. 2. Positive displacement diaphragm type pumps.

NR 811.48(1)(a)3. 3. Digitally controlled constant stroke length positive displacement type pumps.

NR 811.48(1)(a)4. 4. Peristaltic type pumps.

NR 811.48(1)(a)5. 5. Tablet chlorinator type.

NR 811.48(1)(b) (b) Capacity. The chlorinator capacity shall be such that a free chlorine dose of at least 2 mg/L can be attained when maximum flow rates coincide with anticipated maximum chlorine demands. Liquid chemical feed equipment shall be designed to operate in accordance with the requirements under s. NR 811.39 (2) (c). Solution-feed-gas-type chlorination chemical feed equipment shall be designed to operate between 10 percent and 70 percent of the rotameter capacity. This may require that 2 rotameters be provided, one for normal feed rates and one for emergency feed rates. For all chemical feed systems, the emergency feeder setting shall be designed to provide a minimum of 2 mg/L of chlorine.

NR 811.48(1)(c) (c) Standby equipment. Where chlorination is necessary for protection of the water supply, standby equipment of sufficient capacity shall be available to replace the largest unit during shut-downs. Spare parts shall be made available to replace parts subject to scaling, wear, and breakage.

NR 811.48(1)(d) (d) Automatic proportioning. Automatic proportioning chlorinators shall be required where the rate of flow of the water is not reasonably constant or where the rate of flow of the water is not manually controlled.

NR 811.48(2) (2) Point of application. Chlorine application points shall meet the following requirements:

NR 811.48(2)(a) (a) Chlorine shall be applied at a point which will provide the maximum contact time. Provisions shall be made to minimize short-circuiting.

NR 811.48(2)(b) (b) At plants treating surface water, piping provisions shall be made for applying chlorine to the raw water, settled or clarified water, filtered water, and the plant effluent.

NR 811.48(2)(c) (c) At plants treating groundwater, provision shall be made for applying chlorine to the raw water, the clearwell inlet, and the discharge piping as applicable.

NR 811.48(2)(d) (d) At plants treating groundwater where CT is required by the department, provision shall be made for applying chlorine to the raw water, at the inlet to all CT reservoir detention basins, and the high-lift pump discharge piping as required by the department.

NR 811.48(3) (3) Residual testing equipment. Chlorine residual testing equipment shall meet the following requirements:

NR 811.48(3)(a) (a) Chlorine residual testing methodology shall be as specified in s. NR 809.563 (2), Table R. The equipment shall enable measurement of residuals to the nearest 0.1 mg/1 in the range below 0.5 mg/1 and to the nearest 0.2 mg/1 between 0.5 mg/1 to 2.0 mg/1.

NR 811.48 Note Note: It is recommended that all systems, at a minimum, use an instrument using the DPD colorimetric method with a digital readout and a self contained light source. Automatic chlorine residual pacers and recorders are recommended where the chlorine demand varies appreciably over a short period of time.

NR 811.48(3)(b) (b) Water systems that rely on chlorination for inactivation of bacteria or other microorganisms present in the source water shall have continuous chlorine residual analyzers and other equipment that automatically shut down the facility when the chlorine residuals required by the department are not met. The department may approve less than continuous monitoring for municipal water systems serving 3,300 or fewer people and other-than-municipal water systems on a case-by-case basis provided that replacement measures or practices are implemented to provide comparable public health protection.

NR 811.48(4) (4) Gas chlorinator piping. The water supply piping shall be designed to prevent contamination of the treated water supply by sources of impure or unknown quality. Pipes carrying elemental liquid or dry gaseous chlorine under pressure shall be Schedule 80 seamless steel tubing or other materials recommended by the Chlorine Institute. PVC pipe may not be used. Chlorine solution piping and fittings shall be rubber, PVC, polyethylene, or other materials recommended by the Chlorine Institute.

NR 811.48(5) (5) Chlorine gas housing. Chlorine gas feed and storage installations shall meet the following requirements:

NR 811.48(5)(a) (a) Chlorine gas feed and storage installations shall be separated from other operating areas by gas-tight rooms or enclosures in order to prevent injury to personnel and damage to equipment.

NR 811.48(5)(b) (b) Chlorine gas rooms shall be provided with a safety glass inspection window installed in an interior wall or exterior door to permit viewing of the interior of the room and the equipment.

NR 811.48(5)(c) (c) Chlorine gas rooms shall be provided with a minimum of one door having emergency or panic hardware opening outward to the building exterior. Rooms may have additional doors to the building exterior.

NR 811.48(5)(d) (d) Chlorine gas rooms shall be heated to prevent freezing and insure proper operation of the equipment.

NR 811.48(5)(f) (f) Full and empty cylinders of chlorine gas shall be:

NR 811.48(5)(f)1. 1. Isolated from operating areas.

NR 811.48(5)(f)2. 2. Restrained in position to prevent movement of the cylinders.

NR 811.48(5)(f)3. 3. Stored in rooms separate from ammonia storage.

NR 811.48(5)(f)4. 4. Stored in areas not in direct sunlight or exposed to excessive heat.

NR 811.48(5)(g) (g) Pressurized chlorine feed lines may not carry chlorine gas beyond the chlorine room. Vacuum chlorine feed lines may carry gas beyond the chlorine room if the chlorine lines are either schedule 40 polyethylene tubing or schedule 80 PVC pipe. Polyethylene tubing shall be enclosed in a protective conduit running from the chlorine room to a point near the ejector. The end of the conduit in the chlorine room shall be sealed. Polyethylene tubing connections shall be made using tube adaptors especially designed for this purpose. PVC pipe joints may be socket welded using PVC cement or threaded using polytetrafluoroethylene pipe joint tape.

NR 811.48(5)(h) (h) Premanufactured chlorine cabinets may be used for retrofit situations only. These cabinets shall have an observation window, fan, air intake, and light as required in par. (b) and sub. (6) for normal chlorine gas rooms.

NR 811.48 Note Note: It is recommended that these cabinets not be placed on the sunny side of the building.

NR 811.48(6) (6) Ventilation of chlorine gas rooms. Ventilation of chlorine gas rooms shall meet the following requirements:

NR 811.48(6)(a) (a) One complete air change per minute shall be provided when the room is occupied.

NR 811.48(6)(b) (b) The exhaust fan suction shall be within 12 inches of the floor as far as practical from the door and air inlet, with the point of discharge located to avoid contamination of air inlets to other rooms and structures, and to avoid being blocked by snow or other obstructions.

NR 811.48(6)(c) (c) Air inlets shall be located near the ceiling and controlled to prevent adverse temperature variations.

NR 811.48(6)(d) (d) Louvers for the chlorine room air intake and exhaust shall be corrosion resistant and shall facilitate airtight closure.

NR 811.48(6)(e) (e) The exhaust fan switch shall be located outside the entrance to the chlorine room with a signal light indicating fan operation when the fan can be controlled from more than one point. Outside switches shall be protected from vandalism. As an alternative, the fan may be controlled by an automatic door switch with manual shut-off.

NR 811.48 Note Note: It is recommended that switches for fans and lights be interlocked for simultaneous operation.

NR 811.48(6)(f) (f) Vent lines from feeders and storage shall discharge to the outside atmosphere, above grade, in a downward direction, be screened, and be located as required in par. (b). In addition, vent lines shall conform with the manufacturer’s installation recommendations.

NR 811.48(7) (7) Safety equipment. The following safety equipment shall be provided when chlorine gas is used:

NR 811.48(7)(a) (a) Respiratory protection equipment, known as gas masks, meeting the requirements of the National Institute for Occupational Safety and Health (NIOSH) shall be available where chlorine gas is handled, and shall be stored at a convenient heated location, but not inside any room where chlorine is used or stored. The gas masks shall use compressed air, have at least a 30-minute capacity, and be compatible with or exactly the same as the gas masks used by the fire department responsible for the plant. The gas masks shall be available at all installations where chlorine gas is handled and shall be placed outside every room where chlorine gas is used or stored. At installations utilizing 150-pound, or less, cylinders, an agreement with the local fire department that has an approved type of gas mask for the fire department to handle water system chlorine gas leaks may be approved by the department. Instructions for using, testing and replacing gas mask parts shall be posted. Other protective clothing shall be provided as necessary.

NR 811.48(7)(b) (b) A bottle of concentrated ammonium hydroxide, 56 percent ammonia solution, shall be available for chlorine leak detection.

NR 811.48(7)(c) (c) If pressurized chlorine gas is present, continuous chlorine leak detection equipment shall be installed and equipped with both an audible alarm and a warning light. Automatic emergency chlorine cylinder shutdown valves shall also be provided.

NR 811.48(7)(d) (d) If ton cylinders are used, leak repair kits, approved by the Chlorine Institute, shall be available at the waterworks or a nearby fire department.

NR 811.48(8) (8) Ammonia. Ammonia chemical feed installations shall meet all of the following requirements:

NR 811.48(8)(a) (a) Gaseous ammonia. Housing and ventilation for ammoniation shall meet the requirements under subs. (5) and (6) for chlorine, except that the exhaust fan inlet shall be within 12 inches of the ceiling and the fresh air inlet shall be within 12 inches of the floor. Ammonia storage and feed facilities shall be separate from chlorine facilities because of the combustion hazard. A plastic bottle of hydrochloric acid shall be available and used for leak detection.

NR 811.48(8)(b) (b) Ammonium sulfate. Ammonium sulfate chemical feed installation shall meet the chemical storage requirements under s. NR 811.40.

NR 811.48(8)(c) (c) Aqua ammonia. Aqua ammonia installation shall meet all of the following requirements:

NR 811.48(8)(c)1. 1. An aqua ammonia chemical feed and storage system shall be installed in its own dedicated room.

NR 811.48(8)(c)2. 2. Bulk liquid storage tanks and day tanks shall be vented to the outside of the building and discharge downward facing with a 24-mesh corrosion resistant screen a minimum of 24 inches above grade. The chemical tank vents shall be provided with inert liquid traps.