Ill. Admin. Code tit. 35, § 611.533 - Filtered PWSs
A supplier using a surface water source or a groundwater source under the direct influence of surface water and providing filtration treatment must monitor in accordance with this Section.
a) The supplier must perform turbidity
measurements Section 611.250 requires on
representative samples of the PWS's filtered water every four hours (or more
frequently) when the supplier serves water to the public. A supplier may
substitute continuous turbidity monitoring for grab sample monitoring if it
validates the continuous measurement for accuracy on a regular basis using a
protocol the Agency approved in a SEP. For a supplier using slow sand
filtration or filtration treatment other than conventional treatment, direct
filtration, or diatomaceous earth filtration, the Agency must reduce the
sampling frequency to once per day in a SEP if the Agency determines that less
frequent monitoring is sufficient to indicate effective filtration performance.
For a supplier serving 500 or fewer persons, the Agency must reduce the
turbidity sampling frequency to once per day in a SEP if the Agency determines
that less frequent monitoring is sufficient to indicate effective filtration
performance regardless of the type of filtration treatment used.
b) RDC Entering Distribution System
1) Suppliers Serving More Than 3300 Persons.
The supplier must continuously monitor the RDC of the water entering the
distribution system, and the supplier must record the lowest value each day,
except that the supplier may conduct grab sampling every four hours in lieu of
continuous monitoring if there is a failure in the continuous monitoring
equipment, but not for more than five working days following the equipment
failure.
2) Suppliers Serving 3,300
or Fewer Persons. The supplier may take grab samples in lieu of providing
continuous monitoring on an ongoing basis at the frequencies each day Table C
prescribes. If at any time the RDC falls below
0.2 mg/L in a system using grab
sampling in lieu of continuous monitoring, the supplier must take a grab sample
every four hours until RDC is equal to or greater than
0.2 mg/L.
c) Points of Measurement
1) The supplier must measure the RDC at least
at the same points in the distribution system and at the same time as sampling
total coliforms, as Sections
611.1054 through
611.1058 specify. The Agency
must allow a supplier using both a surface water source and a groundwater
source or a groundwater source under direct influence of surface water and a
groundwater source to take RDC samples at points other than the total coliform
sampling points if the Agency determines that such points are more
representative of treated (disinfected) water quality within the distribution
system. The supplier may measure HPC, as Section
611.531(a)
specifies, in lieu of RDC.
2)
Subsection (c)(1) does not apply if the Agency determines under Section
611.213(c) that
a system has no means for having a certified laboratory analyze a sample for
PHC under the requisite time and temperature conditions Section
611.531(a)
specifies and the supplier provides adequate disinfection in its distribution
system.
Notes
Amended at 38 Ill. Reg. 3608, effective January 27, 2014
BOARD NOTE: This Section derives from 40 CFR 141.74(c).
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