Current through August 26, 2024
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.
(1) CONVENTIONAL FILTRATION TREATMENT.
(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.
(b) The turbidity level of representative
samples of a system's filtered water may not exceed one NTU, measured as
specified in s.
NR 809.113(1) Tables A and B.
(c) To determine compliance with par. (a),
turbidity measurements shall be performed on representative samples of filtered
water at least every 4 hours that the system serves water to the public.
(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.
(e) A system that uses lime softening may
acidify representative samples prior to analysis if using a protocol approved
by the department.
(2) DIRECT FILTRATION.
(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.
(b) The
turbidity level of representative samples of a system's filtered water may not
exceed 1 NTU, measured as specified in s.
NR 809.113(1), Tables A and B.
(3) SLOW SAND FILTRATION.
(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.
(b) The turbidity level of representative
samples of a system's filtered water may not exceed 5 NTU, measured as
specified in s.
NR 809.113(1), Tables A and B.
(4) DIATOMACEOUS EARTH FILTRATION.
(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.
(b) The turbidity level of representative
samples of a system's filtered water may not exceed 5 NTU, measured as
specified in s.
NR 809.113(1), Tables A and B.
(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.
