NR 810.27(1)(1) This subchapter establishes criteria under which filtration is required as a treatment technique for public water systems supplied by a surface water source or a groundwater source under the direct influence of surface water. Direct influence shall be determined for individual sources by the department. The department determination of direct influence may be based on site-specific measurements of water quality characteristics such as those stated in s. NR 810.02 (25) or documentation of well construction characteristics and geology with field evaluation. These regulations also establish requirements for treatment techniques in lieu of maximum contaminant levels for Giardia lamblia, viruses, heterotrophic plate count bacteria, Legionella, Cryptosporidium and turbidity. Treatment technique requirements apply to every public water system which utilizes surface water or groundwater under the direct influence of surface water and the requirements consist of installing and properly operating water treatment processes which reliably achieve:

NR 810.27(1)(a)(a) At least 99.9% or 3-log removal or inactivation of Giardia lamblia cysts between a point where the raw water is not subject to recontamination by surface water runoff and a point downstream before or at the first customer.

NR 810.27(1)(b)(b) At least 99.99% or 4-log removal or inactivation of viruses between a point where the raw water is not subject to recontamination by surface water runoff and a point downstream before or at the first customer.

NR 810.27(1)(c)(c) At least 99.9% or 3-log removal of Cryptosporidium between a point where the raw water is not subject to recontamination by surface water runoff and a point downstream before or at the first customer for filtered systems, or Cryptosporidium control under the watershed control system for unfiltered GWUDI systems.

NR 810.27(2)(2) A public water system using a surface water source is considered to be in compliance with the requirements of sub. (1) if it meets the filtration requirements in s. NR 810.29 and the disinfection requirements in s. NR 810.31.

NR 810.27(3)(3) A public water system using groundwater under the direct influence of surface water is considered to be in compliance with the requirements or sub. (1) if it meets the criteria for avoiding filtration in s. NR 810.30 along with the disinfection requirements in s. NR 810.31; or if it meets the filtration requirements in s. NR 810.29 and it meets the disinfection requirements in s. NR 810.31.

NR 810.27(4)(4) Each public water system using a surface water source or a groundwater under the direct influence of surface water shall be operated by qualified personnel who meet the requirements specified by the department.

NR 810.28NR 810.28 Requirements for covers on water storage structures. All finished water storage reservoirs and treatment plant basins shall be covered. Finished water is that water which has received all required treatment. Treatment plant basins contain water at various stages of treatment.

NR 810.29NR 810.29 Basic filtration requirements. Public water systems that use a surface water source shall provide filtration which complies with the requirements of sub. (1), (2), (3), (4), or (5) and meets the disinfection criteria specified in s. NR 810.31 (2). Public water systems that use a groundwater source under the direct influence of surface water shall provide filtration which complies with the specifications of sub. (1), (2), (3), (4) or (5) and meets the disinfection criteria specified in s. NR 810.31 (2) within 18 months of the date that a source is determined, by the department, to be under the direct influence of surface water unless they meet the filtration avoidance criteria in s. NR 810.30. Failure to meet the applicable requirements of this section is a treatment technique violation.

NR 810.29(1)(1) Conventional filtration treatment.

NR 810.29(1)(a)(a) For systems using conventional filtration treatment, the turbidity level of representative samples of a system’s filtered water shall be less than or equal to 0.3 nephelometric turbidity units (NTU) in at least 95% of the measurements taken each month, measured as specified in s. NR 809.113 (1) Tables A and B.

NR 810.29(1)(d)(d) In lieu of the requirements of par. (c), turbidity measurements from a continuous reading and recording turbidity monitoring device shall be recorded at predetermined 4-hour intervals to determine compliance with par. (a). The highest turbidity measurement recorded at any time during the day shall be reported under s. NR 809.80 (7) (a) 1.

NR 810.29(2)(2) Direct filtration.

NR 810.29(2)(a)(a) For systems using direct filtration, the turbidity level of representative samples of a system’s filtered water shall be less than or equal to 0.3 NTU in at least 95% of the measurements taken each month, measured as specified in s. NR 809.113 (1), Tables A and B. The department may approve a turbidity limit up to one NTU if the water supplier provides the department with documentation which reliably indicates the system achieves at least 99.9% removal or inactivation of Giardia lamblia cysts at a turbidity level above 0.5 NTU at least 95% of the time that the system delivers water to the public.

NR 810.29(3)(3) Slow sand filtration.

NR 810.29(3)(a)(a) For systems using slow sand filtration, the turbidity level of representative samples of a system’s filtered water shall be less than or equal to 1 NTU in at least 95% of the measurements taken each month, measured as specified in s. NR 809.113 (1), Tables A and B.

NR 810.29(4)(4) Diatomaceous earth filtration.

NR 810.29(4)(a)(a) For systems using diatomaceous earth filtration, the turbidity level of representative samples of a system’s filtered water shall be less than or equal to one NTU in at least 95% of the measurements taken each month, measured as specified in s. NR 809.113 (1), Tables A and B.

NR 810.29(5)(5) Other filtration technologies. A public water system may use a filtration technology not listed in subs. (1) to (4) if the water supplier for the system demonstrates to the department, using pilot studies or other means, that the alternative filtration technology, in combination with disinfection treatment that meets the requirements of s. NR 810.31, consistently achieves 99.9% removal or inactivation of Giardia lamblia cysts and 99.99% removal or inactivation of viruses, and 99.9% removal of Cryptosporidium oocysts, and the department approves the use of the filtration technology. For each approval, the department shall set turbidity performance requirements that the water system shall meet at least 95% of the time at a level that consistently achieves 99.9% removal or inactivation of Giardia lamblia cysts, 99.99% removal or inactivation of viruses, and 99% removal of Cryptosporidium oocysts. The department may set other performance requirements to assure the integrity of the technology.