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)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)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)12.
12. The inlet piping shall be supported separately from the tower's main structural support.
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)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)1.
1. Loss of head gauges on the inlet and outlet pipes of each filter.
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)(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.
NR 811.54(1)(b)
(b) When ozone is used as a disinfectant, ozonation and detention shall provide the required disinfection CT value. Additionally, application of a disinfectant which maintains a measurable residual in the distribution system shall be required.
NR 811.54(1)(c)
(c) Where ozonation is approved by the department to be used for disinfection of a bacteriologically unsafe water supply, duplicate process streams shall be provided. This includes air supply, air preparation equipment, ozone generators, ozone contact chambers, ozone diffusers, power supply, and post disinfection equipment. This requirement may be waived by the department where other acceptable water sources having sufficient capacity are available.
NR 811.54(2)
(2)
Feed gas preparation. Feed gas can be air, oxygen enriched air, or high purity oxygen. Sources of high purity oxygen include purchased liquid oxygen; on site generation using cryogenic air separation; or temperature, pressure or vacuum swing, adsorptive separation, technology. For high purity oxygen-feed systems, dryers typically are not required. Feed gas preparation shall meet the following requirements:
NR 811.54(2)(a)
(a) Air handling equipment. Air handling equipment on conventional low pressure air-feed systems shall consist of an air compressor unless drawn by vacuum, water or air separator, refrigerant and desiccant dryers and particulate filters. For oxygen-feed systems, compressors, separators, and dryers may not be required by the department depending on the purity of the oxygen. In all cases the design shall ensure that the maximum dew point of -60
°C (-76
°F) will not be exceeded at any time.
NR 811.54(2)(b)1.1. Air compressors shall be of the liquid-ring or rotary lobe, oil-less, positive displacement type for smaller systems or dry rotary screw compressors for larger systems.
NR 811.54(2)(b)2.
2. The air compressors shall have the capacity to simultaneously provide for maximum ozone demand, provide the air flow required for purging the desiccant dryers, where required, and allow for standby capacity.
NR 811.54(2)(b)3.
3. Air feed for the compressor shall be drawn from a point protected from rain, snow, condensation, mist, and fog to minimize moisture content of the air supply. The air feed shall be protected from contaminated air sources. Outside air intakes shall consist of a downturned pipe elbow installed at a location least susceptible to vandalism and covered with a 24-mesh corrosion resistant screen.
NR 811.54(2)(b)4.
4. A compressed air after-cooler or entrainment separator or both with automatic drain shall be provided prior to the dryers to reduce the water vapor.
NR 811.54(2)(c)1.1. Dry, dust-free, and oil-free feed gas shall be provided to the ozone generator. Sufficient drying to a maximum dew point of -60
°C (-76
°F) shall be provided at the end of the drying cycle.
NR 811.54(2)(c)2.
2. Drying for high pressure systems shall be accomplished using desiccant dryers. For low pressure systems, a refrigeration air dryer in series with desiccant dryers shall be used.
NR 811.54(2)(c)3.
3. A refrigeration dryer capable of reducing the inlet air temperature to 4
°C (40
°F) shall be provided for low pressure air preparation systems. The dryer may be of the compressed refrigerant type or chilled water type.
NR 811.54(2)(c)4.
4. The desiccant dryers shall be of the external heated or heatless type.
NR 811.54(2)(c)5.
5. For heat-reactivated desiccant dryers, the unit shall contain 2 desiccant filled towers complete with pressure relief valves, 2 4-way valves and a heater. In addition, external type dryers shall have a cooler unit and blowers. The size of the unit shall be such that the specified dew point will be achieved during a minimum absorption cycle time of 16 hours while operating at the maximum expected moisture loading conditions.
NR 811.54(2)(c)6.
6. Each dryer shall be capable of venting dry gas to the atmosphere, prior to the ozone generator, to allow start-up when other dryers are on-line.
NR 811.54(2)(d)1.1. Air filters shall be provided on the suction side of the air compressors, between the air compressors and the dryers and between the dryers and the ozone generators.
NR 811.54(2)(d)2.
2. The filter before the compressor shall be of the coalescing type and be capable of removing all particles larger than 10 microns in diameter. The filter before the dryer shall be of the coalescing type and be capable of removing all particles larger than 0.3 microns in diameter. The filter after the dryer shall be of the particulate type and be capable of removing all particles larger than 0.1 microns in diameter or a size specified by the generator manufacturer.
NR 811.54(2)(e)
(e)
Air preparation piping. Piping in a compressed air preparation system shall be common grade steel, seamless copper, stainless steel, or galvanized steel. The piping shall be designed to withstand the maximum pressures in the air preparation system. PVC piping may be used in a vacuum air preparation system when located and supported to be protected from physical damage including from heat.
NR 811.54(3)
(3)
Ozone generators. Ozone generators shall meet the following requirements:
NR 811.54(3)(a)
(a) Capacity. The production rating of the ozone generators shall be provided in pounds per day and pounds per kilowatt-hour. The capacity of any ozone generators shall be determined by ozone demand tests including tests under critical conditions. Where ozone is approved for use by the department as a disinfectant, the generators shall be sized in conjunction with the detention basins to provide the required inactivation CT values for viruses,
Giardia lamblia, and
Cryptosporidium contained in ss.
NR 810.59,
810.60, and
810.61.
NR 811.54(3)(a)1.
1. The design shall ensure that the minimum concentration of ozone in the generator exit gas will be 1.0% by weight.
NR 811.54(3)(a)2.
2. Generators shall be sized to have sufficient reserve capacity so that the system does not operate at peak capacity for extended periods of time. Low, medium, and high frequency systems which operate at lower peak voltages require less reserve capacity.
NR 811.54(3)(a)3.
3. Generators with individual dielectrics shall have the capability of operating satisfactorily while individual dielectrics are out-of-service. This shall be accomplished through the use of individually fused dielectrics.
NR 811.54(3)(a)4.
4. At least 2 generators, each with a capacity of supplying the normal ozone demand, shall be provided. If determined by the department to be not critical to maintaining production capacity, smaller installations employing ozone generators with multiple individually fused dielectrics may be able to employ a fewer number of generators each having excess ozone production capacity.
NR 811.54(3)(a)5.
5. If there is to be a variation in the supply temperature of the generator cooling water throughout the year, then curves or other data shall be furnished to the department to show ozone production changes due to the varying temperature of the supplied cooling water. The design shall ensure that the generators can produce the required ozone at the maximum coolant temperature.
NR 811.54(3)(b)
(b) Electrical. The generators may be low, medium, or high frequency type. The specifications shall require that the transformers and other electrical hardware be proven, high quality components designed for ozone service.
