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)(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 HistoryHistory: 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(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.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)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.