Current through Register Vol. 48, No. 38, September 20, 2024
a) Applicability. A Subpart B system supplier
that serves fewer than 10,000 persons, which is required to filter, and which
utilizes filtration other than slow sand filtration or diatomaceous earth
filtration must meet the combined filter effluent turbidity requirements of
subsections (b) through (d). If the supplier uses slow sand or diatomaceous
earth filtration the supplier is not required to meet the combined filter
effluent turbidity limits of this Subpart X, but the supplier must continue to
meet the combined filter effluent turbidity limits in Section
611.250.
b) Combined Filter Effluent Turbidity Limits.
A supplier must meet two strengthened combined filter effluent turbidity
limits.
1) The first combined filter effluent
turbidity limit is a "95th percentile" turbidity
limit that a supplier must meet in at least 95 percent of the turbidity
measurements taken each month. Measurements must continue to be taken as
described in Sections
611.531
and
611.533. Monthly
reporting must be completed according to Section
611.957(a).
The following are the required limits for specific filtration technologies:
A) For a system with conventional filtration
or direct filtration, the 95th percentile turbidity
value is 0.3 NTU.
B) For a system
with any other alternative filter technology, the
95th percentile turbidity value is a value (not to
exceed 1 NTU) to be determined by the Agency, by a SEP, based on the
demonstration described in subsection (c).
2) The second combined filter effluent
turbidity limit is a "maximum" turbidity limit that a supplier may at no time
exceed during the month. Measurements must continue to be taken as described in
Sections
611.531
and 611.533. Monthly reporting must be completed according to Section
611.957(a).
The following are the required limits for specific filtration technologies:
A) For a system with conventional filtration
or direct filtration, the maximum turbidity value is 1 NTU.
B) For a system with any other alternative
filter technology, the maximum turbidity value is a value (not to exceed 5 NTU)
to be determined by the Agency, by a SEP, based on the demonstration described
in subsection (c).
c) Requirements for an Alternative Filtration
System
1) If a supplier's system consists of
alternative filtration (filtration other than slow sand filtration,
diatomaceous earth filtration, conventional filtration, or direct filtration)
the supplier is required to conduct a demonstration (see tables in subsection
(b)). The supplier must demonstrate to the Agency, using pilot plant studies or
other means, that its system's filtration, in combination with disinfection
treatment, consistently achieves the following:
A) 99 percent removal of Cryptosporidium
oocysts;
B)99.9 percent removal or
inactivation of Giardia lamblia cysts; and
C)99.99 percent removal or inactivation of
viruses.
2) This
subsection (c)(2) corresponds with
40
CFR 141.552(b), which USEPA
has designated as "reserved". This statement maintains structural
correspondence with the corresponding federal regulation.
d) Requirements for a Lime-Softening System.
If a supplier practices lime softening, the supplier may acidify representative
combined filter effluent turbidity samples prior to analysis using a protocol
approved by the Agency.
BOARD NOTE: Derived from
40
CFR 141.550 through
141.553.
