(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.
