NR 811.48(10) (10) Sodium chlorite for chlorine dioxide generation. Proposals for the storage and use of sodium chlorite shall be submitted to the department for approval. Department approval shall be obtained prior to the preparation of final plans and specifications. Provision shall be made for proper storage and handling of sodium chlorite to eliminate any danger of fire or explosion.

NR 811.48(10)(a) (a) Storage.

NR 811.48(10)(a)1. 1. Sodium chlorite shall be stored by itself in a separate room and preferably shall be stored in an outside building detached from the water treatment facility. Sodium chlorite shall be stored away from organic materials with which it could react violently.

NR 811.48(10)(a)2. 2. Storage structures shall be constructed of noncombustible materials.

NR 811.48(10)(a)3. 3. If the storage structure is located in an area where a fire may occur, water shall be available to keep the sodium chlorite area cool enough to prevent heat induced explosive decomposition of the sodium chlorite.

NR 811.48(10)(b) (b) Handling.

NR 811.48(10)(b)1. 1. Care shall be taken to prevent spillage of sodium chlorite.

NR 811.48(10)(b)2. 2. An emergency plan of operation shall be available for the clean up of any spillage.

NR 811.48(10)(b)3. 3. Storage drums containing sodium chlorite shall be thoroughly flushed and the waste shall be discharged to an acceptable location prior to recycling or disposal.

NR 811.48(10)(c) (c) Feeders.

NR 811.48(10)(c)1. 1. Chemical feed pumps shall meet the requirements of s. NR 811.39 (2).

NR 811.48(10)(c)2. 2. Tubing for conveying sodium chlorite or chlorine dioxide solutions shall be Type 1 PVC, polyethylene or materials recommended by the manufacturer.

NR 811.48(10)(c)3. 3. Chemical feeders may be installed in chlorine gas rooms if sufficient space is provided or in separate rooms meeting the requirements of subs. (5) and (6).

NR 811.48(10)(c)4. 4. Feed lines shall be installed in a manner to prevent formation of gas pockets and shall terminate at a point of positive pressure.

NR 811.48(10)(c)5. 5. Check valves shall be provided to prevent the backflow of chlorine into the sodium chlorite line.

NR 811.48 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (1) (a) 2. to 4., (b), (4) (title), (5) (title), r. (5) (e), am. (6) (b), (7) (a), r. and recr. (8) Register January 2024 No. 817, eff. 2-1-24.

NR 811.49 NR 811.49 Filtration — gravity. The application of any type of gravity filter and media shall be supported by water quality data representing a period of use sufficient to characterize any variations in water quality. Experimental or pilot plant treatment studies may be required to demonstrate the applicability of the method or rate of filtration proposed. Pressure filters will not be approved for surface water applications. The following specific requirements shall be met:

NR 811.49(1) (1) Rapid rate gravity filters.

NR 811.49(1)(a) (a) Pretreatment. Rapid rate gravity filters may only be utilized after coagulation, flocculation and sedimentation.

NR 811.49(1)(b) (b) Number. At least 2 filter units or cells shall be provided. Provisions shall be made to meet the plant design capacity at the approved filtration rate with one filter out of service. If only 2 units or cells are provided, each shall be capable of meeting the plant design capacity, normally the projected maximum daily demand.

NR 811.49(1)(c) (c) Rate of filtration. The permissible rate of filtration shall be determined after consideration of factors such as raw water quality, degree of pretreatment provided, filter media, water quality control parameters, competency of operating personnel, and other factors required by the department. If effective coagulation, flocculation, sedimentation, and filtration processes are to be utilized with relatively clean water sources, the following filtration rates may be approved:

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In all cases, the filtration rate shall be proposed and justified by the design engineer and shall be approved by the department prior to the preparation of final plans and specifications. The department may approve higher rates than indicated in this paragraph with sufficient justification by the design engineer or through pilot testing under s. NR 811.44.

NR 811.49(1)(d) (d) Structural details and hydraulics. The filter structure shall be designed to provide:

NR 811.49(1)(d)1. 1. Vertical walls within the filter.

NR 811.49(1)(d)2. 2. No protrusion of the filter walls or other structures into the filter media or the area between the top of the media and the high water line during backwashing.

NR 811.49(1)(d)3. 3. Cover by superstructure.

NR 811.49(1)(d)4. 4. Head room to permit normal inspection and operation.

NR 811.49(1)(d)5. 5. Minimum filter box depth of 8.5 feet.