Section NR 210.06 - Disinfection requirements(1) DISINFECTION REQUIREMENTS. Disinfection shall be required of dischargers subject to the provisions of this chapter when the department determines, based on the information identified in sub. (3), the discharge of wastewater poses a risk to human and animal health. Disinfection shall be required: (a) From May 1 through September 30 annually to protect recreational uses, or(b) Year-round to protect public drinking water supplies.(c) The period during which disinfection under pars. (a) and (b) is required may be adjusted in a WPDES permit where necessary to protect human and animal health. (2) EFFLUENT LIMITATIONS. Where and when disinfection is required, the following effluent limitations shall apply: (a)Bacterial indicators.1. 'Recreation protection.' During the period of disinfection to protect recreational uses as determined under sub. (1) (a) or (c), all of the following shall apply:a. The geometric mean of E. coli bacteria in effluent samples collected in any calendar month may not exceed 126 counts/100 mL. Note: To calculate the geometric mean, a value of 1 should be used for any result of 0.
Note: As specified in ch. NR 102, Table A, for determining attainment or compliance with bacteria criteria or limits, counts are equivalent to either colony forming units or most probable number.
b. No more than 10 percent of E. coli bacteria samples collected in any calendar month may exceed 410 counts/100 mL. Note: U.S. EPA developed the E. coli criteria in s. NR 102.04(6), on which these effluent limits are based using membrane filtration to count E. coli colony forming units.
2. 'Public drinking water supply protection.' If a facility is required to disinfect to protect public drinking water supplies outside of the recreation period specified in sub. (1) (a) or (c), it may either continue to meet the E. coli limits specified in par. (a) 1. year-round, or the geometric mean of the fecal coliform bacteria for effluent samples collected in a period of 30 consecutive days may not exceed 400 counts/100 mL. (b)Chlorine.When chlorine is used for disinfection, the daily maximum total residual chlorine concentration of the discharge may not exceed 0.1mg/l. In addition, when chlorine is used for disinfection, a dechlorination process shall be in operation for the period during which disinfection is required. Note: The 0.1 mg/l total residual chlorine limit reflects best analytical technique for domestic wastewater effluents. An effluent limitation for total residual chlorine based on best available technology for dechlorination of effluents was determined to be below detection levels of currently available analytical techniques.
Note: Compliance schedules for effluent limits established under this subsection are authorized in s. NR 205.14 and procedures are detailed in s. NR 106.117. Language on tentative and final determinations related to the permit, public notice processes, and review procedures are provided for all facilities in ch. NR 203.
(3) DISINFECTION DETERMINATION. A permittee subject to this chapter shall at the time of application for a WPDES permit provide information identified in this subsection which the department shall use in the determination of the need for effluent disinfection. The following information shall be used in identifying risks to human and animal health: (a) Proximity of the wastewater outfall to swimming beaches and other waters which have a high level of human contact recreational activities.(b) Proximity of the wastewater outfall to public drinking water supply intakes. At a minimum, whenever a drinking water intake is within a radius of 5 miles of a wastewater outfall in a lake or impoundment or within 20 miles downstream of a wastewater outfall on a flowing surface water, disinfection shall be provided.(c) Proximity of the wastewater outfall to wetlands which support populations of waterfowl subject to disease outbreaks, which may be caused by the discharge of wastewater which has not been disinfected.(d) Quality of the wastewater being discharged.(e) Dilution and mixing characteristics of the wastewater with the receiving water.(f) Bacterial indicator organism levels or sanitary survey results from sampling conducted in the vicinity of the wastewater outfall and near the sites used for recreational purposes.(g) The classification of the receiving water and downstream waters as determined in s. NR 104.02(1).(h) The detention time of the wastewater treatment system. Except in extenuating circumstances, the discharge of wastewater to surface water from a treatment system with a detention time of 180 days or longer does not pose a risk to human and animal health.(i) Other factors that are necessary to determine if there is a risk posed to human and animal health by the discharge of wastewater that has not been disinfected.(7) DISINFECTION CONTINUATION. In the absence of a specific determination under sub. (1), all dischargers which are required to disinfect as of November 1, 1986, or thereafter shall continue to disinfect.Wis. Admin. Code Department of Natural Resources NR 210.06
Cr. Register, October, 1986, No. 370, eff. 11-1-86.Amended by, CR 19-014: cr. (1) (title), (2) (title), am. (2) (intro.), r. and recr. (2) (a), cr. (2) (b) (title), (3) (title), r. (4) to (6), am. (7) Register April 2020 No. 772, eff. 5-1-20; correction in (7) made under s. 35.17, Stats., Register April 2020 No. 772, eff. 5/1/2020