Current through Register Vol. 48, No. 38, September 20, 2024
a) Bag
and Cartridge Filters. A supplier receives Cryptosporidium treatment credit of
up to 2.0 -log for individual bag or cartridge filters and up to 2.5 -log for
bag or cartridge filters operated in series by meeting the criteria set forth
in subsections (a)(1) through (a)(10). To be eligible for this credit, the
supplier must report the results of challenge testing that meets the
requirements of subsections (a)(2) through (a)(9) to the Agency. The filters
must treat the entire plant flow taken from a Subpart B source.
1) The Cryptosporidium treatment credit
awarded to bag or cartridge filters must be based on the removal efficiency
demonstrated during challenge testing that is conducted according to the
criteria set forth in subsections (a)(2) through (a)(9). A factor of safety
equal to 1-log for individual bag or cartridge filters and 0.5 -log for bag or
cartridge filters in series must be applied to challenge testing results to
determine removal credit. A supplier may use results from challenge testing
conducted prior to January 5, 2006 if the prior testing was consistent with the
criteria specified in subsections (a)(2) through (a)(9).
2) Challenge testing must be performed on
full-scale bag or cartridge filters, and the associated filter housing or
pressure vessel, that are identical in material and construction to the filters
and housings the supplier will use for removal of Cryptosporidium. Bag or
cartridge filters must be challenge tested in the same configuration that the
supplier will use, either as individual filters or as a series configuration of
filters.
3) Challenge testing must
be conducted using Cryptosporidium or a surrogate that is removed no more
efficiently than Cryptosporidium. The microorganism or surrogate used during
challenge testing is referred to as the challenge particulate. The
concentration of the challenge particulate must be determined using a method
capable of discreetly quantifying the specific microorganism or surrogate used
in the test; gross measurements such as turbidity may not be used.
4) The maximum feed water concentration that
can be used during a challenge test must be based on the detection limit of the
challenge particulate in the filtrate (i.e., filtrate detection limit) and must
be calculated using the following equation:
Maximum Feed Concentration = 1 x
104 x (Filtrate Detection Limit)
5) Challenge testing must be conducted at the
maximum design flow rate for the filter as specified by the
manufacturer.
6) Each filter
evaluated must be tested for a duration sufficient to reach 100 percent of the
terminal pressure drop, which establishes the maximum pressure drop under which
the filter may be used to comply with the requirements of this Subpart
Z.
7) Removal efficiency of a
filter must be determined from the results of the challenge test and expressed
in terms of log removal values using the following equation:
LRV = Log10
(Cf) - Log10
(Cp)
Where:
|
LRV
|
=
|
log removal value demonstrated during challenge
testing
|
|
Cf
|
=
|
the feed concentration measured during the challenge
test
|
|
Cp
|
=
|
the filtrate concentration measured during the
challenge test. In applying this equation, the same units must be used for the
feed and filtrate concentrations. If the challenge particulate is not detected
in the filtrate, then the term Cp must be set equal to
the detection limit.
|
8)
Each filter tested must be challenged with the challenge particulate during
three periods over the filtration cycle: within two hours after start-up of a
new filter; when the pressure drop is between 45 and 55 percent of the terminal
pressure drop; and at the end of the cycle after the pressure drop has reached
100 percent of the terminal pressure drop. An LRV must be calculated for each
of these challenge periods for each filter tested. The LRV for the filter
(LRVfilter) must be assigned the value of the minimum
LRV observed during the three challenge periods for that filter.
9) If fewer than 20 filters are tested, the
overall removal efficiency for the filter product line must be set equal to the
lowest LRVfilter among the filters tested. If 20 or more
filters are tested, the overall removal efficiency for the filter product line
must be set equal to the 10th percentile of the set
of LRVfilter values for the various filters tested. The
percentile is defined by (i/(n+1)) where i is the rank of n individual data
points ordered lowest to highest. If necessary, the
10th percentile may be calculated using linear
interpolation.
10) If a previously
tested filter is modified in a manner that could change the removal efficiency
of the filter product line, challenge testing to demonstrate the removal
efficiency of the modified filter must be conducted and submitted in writing to
the Agency.
b) Membrane
Filtration
1) A supplier receives
Cryptosporidium treatment credit for membrane filtration that meets the
criteria of this subsection (b). Membrane cartridge filters that meet the
definition of membrane filtration in Section
611.102
are eligible for this credit. The level of treatment credit a supplier receives
is equal to the lower of the following values:
A) The removal efficiency demonstrated during
challenge testing conducted under the conditions in subsection (b)(2);
or
B) The maximum removal
efficiency that can be verified through direct integrity testing used with the
membrane filtration process under the conditions in subsection
(b)(3).
2) Challenge
Testing. The membrane used by the supplier must undergo challenge testing to
evaluate removal efficiency, and the supplier must report the results of
challenge testing to the Agency. Challenge testing must be conducted according
to the criteria set forth in subsections (b)(2)(A) through (b)(2)(G). A
supplier may use data from challenge testing conducted prior to January 5, 2006
if the prior testing was consistent with the criteria set forth in subsections
(b)(2)(A) through (b)(2)(G).
A) Challenge
testing must be conducted on either a full-scale membrane module, identical in
material and construction to the membrane modules used in the supplier's
treatment facility, or a smaller-scale membrane module, identical in material
and similar in construction to the full-scale module. A module is defined as
the smallest component of a membrane unit in which a specific membrane surface
area is housed in a device with a filtrate outlet structure.
B) Challenge testing must be conducted using
Cryptosporidium oocysts or a surrogate that is removed no more efficiently than
Cryptosporidium oocysts. The organism or surrogate used during challenge
testing is referred to as the challenge particulate. The concentration of the
challenge particulate, in both the feed and filtrate water, must be determined
using a method capable of discretely quantifying the specific challenge
particulate used in the test; gross measurements such as turbidity may not be
used.
C) The maximum feed water
concentration that can be used during a challenge test is based on the
detection limit of the challenge particulate in the filtrate and must be
determined according to the following equation:
|
Maximum Feed Concentration
|
=
|
3.16 x 106 x (Filtrate
Detection Limit)
|
D)
Challenge testing must be conducted under representative hydraulic conditions
at the maximum design flux and maximum design process recovery specified by the
manufacturer for the membrane module. Flux is defined as the throughput of a
pressure driven membrane process expressed as flow per unit of membrane area.
Recovery is defined as the volumetric percent of feed water that is converted
to filtrate over the course of an operating cycle uninterrupted by events such
as chemical cleaning or a solids removal process (i.e., backwashing).
E) Removal efficiency of a membrane module
must be calculated from the challenge test results and expressed as a log
removal value according to the following equation:
LRV = Log10
(Cf) - Log10
(Cp)
Where:
|
LRV
|
=
|
log removal value demonstrated during the challenge
test
|
|
Cf
|
=
|
the feed concentration measured during the challenge
test
|
|
Cp
|
=
|
the filtrate concentration measured during the
challenge test. Equivalent units must be used for the feed and filtrate
concentrations. If the challenge particulate is not detected in the filtrate,
the term Cp is set equal to the detection limit for the
purpose of calculating the LRV. An LRV must be calculated for each membrane
module evaluated during the challenge test.
|
F)
The removal efficiency of a membrane filtration process demonstrated during
challenge testing must be expressed as a log removal value
(LRVC-Test). If fewer than 20 modules are tested, then
LRVC-Test is equal to the lowest of the representative
LRVs among the modules tested. If 20 or more modules are tested, then
LRVC-Test is equal to the
10th percentile of the representative LRVs among the
modules tested. The percentile is defined by (i/(n+1)) where i is the rank of n
individual data points ordered lowest to highest. If necessary, the
10th percentile may be calculated using linear
interpolation.
G) The challenge
test must establish a quality control release value (QCRV) for a
non-destructive performance test that demonstrates the Cryptosporidium removal
capability of the membrane filtration module. This performance test must be
applied to each production membrane module used by the supplier that was not
directly challenge tested in order to verify Cryptosporidium removal
capability. Production modules that do not meet the established QCRV are not
eligible for the treatment credit demonstrated during the challenge
test.
H) If a previously tested
membrane is modified in a manner that could change the removal efficiency of
the membrane or the applicability of the non-destructive performance test and
associated QCRV, additional challenge testing to demonstrate the removal
efficiency of, and determine a new QCRV for, the modified membrane must be
conducted and submitted to the Agency.
3) Direct Integrity Testing. A supplier must
conduct direct integrity testing in a manner that demonstrates a removal
efficiency equal to or greater than the removal credit awarded to the membrane
filtration process and meets the requirements described in subsections
(b)(3)(A) through (b)(3)(F). A "direct integrity test" is defined as a physical
test applied to a membrane unit in order to identify and isolate integrity
breaches (i.e., one or more leaks that could result in contamination of the
filtrate).
A) The direct integrity test must
be independently applied to each membrane unit in service. A membrane unit is
defined as a group of membrane modules that share common valving that allows
the unit to be isolated from the rest of the treatment system for the purpose
of integrity testing or other maintenance.
B) The direct integrity method must have a
resolution of three micrometers or less, where resolution is defined as the
size of the smallest integrity breach that contributes to a response from the
direct integrity test.
C) The
direct integrity test must have a sensitivity sufficient to verify the log
treatment credit awarded to the membrane filtration process by the Agency,
where sensitivity is defined as the maximum log removal value that can be
reliably verified by a direct integrity test. Sensitivity must be determined
using the appropriate of the following approaches, considering the type of
direct integrity test the supplier uses:
i)
For a direct integrity test that uses an applied pressure or vacuum, the direct
integrity test sensitivity must be calculated according to the following
equation:
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Where:
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LRVDIT
|
=
|
the sensitivity of the direct integrity test
|
|
Qp
|
=
|
total design filtrate flow from the membrane
unit
|
|
Qbreach
|
=
|
flow of water from an integrity breach associated
with the smallest integrity test response that can be reliably measured
|
|
VCF
|
=
|
volumetric concentration factor. The volumetric
concentration factor is the ratio of the suspended solids concentration on the
high pressure side of the membrane relative to that in the feed water;
or
|
ii)
For a direct integrity test that uses a particulate or molecular marker, the
direct integrity test sensitivity must be calculated according to the following
equation:
LRVDIT = Log10
(Cf) - Log10
(Cp)
Where:
|
LRVDIT
|
=
|
the sensitivity of the direct integrity test
|
|
Cf
|
=
|
the typical feed concentration of the marker used in
the test
|
|
Cp
|
=
|
the filtrate concentration of the marker from an
integral membrane unit
|
D) A supplier must establish a control limit
within the sensitivity limits of the direct integrity test that is indicative
of an integral membrane unit capable of meeting the removal credit awarded by
the Agency.
E) If the result of a
direct integrity test exceeds the control limit established under subsection
(b)(3)(D), the supplier must remove the membrane unit from service. The
supplier must conduct a direct integrity test to verify any repairs, and it may
return the membrane unit to service only if the direct integrity test is within
the established control limit.
F) A
supplier must conduct direct integrity testing on each membrane unit at a
frequency of not less than once each day that the membrane unit is in
operation. The Agency may, by a SEP, approve less frequent testing, based on
demonstrated process reliability, the use of multiple barriers effective for
Cryptosporidium, or reliable process safeguards.
4) Indirect Integrity Monitoring. A supplier
must conduct continuous indirect integrity monitoring on each membrane unit
according to the criteria in subsections (b)(4)(A) through (b)(4)(E). "Indirect
integrity monitoring" is defined as monitoring some aspect of filtrate water
quality that is indicative of the removal of particulate matter. A supplier
that implements continuous direct integrity testing of membrane units in
accordance with the criteria in subsections (b)(3)(A) through (b)(3)(E) is not
subject to the requirements for continuous indirect integrity monitoring. The
supplier must submit a monthly report to the Agency summarizing all continuous
indirect integrity monitoring results triggering direct integrity testing and
the corrective action that was taken in each case.
A) Unless the Agency approves an alternative
parameter by a SEP, continuous indirect integrity monitoring must include
continuous filtrate turbidity monitoring.
B) Continuous indirect integrity monitoring
must be conducted at a frequency of no less than once every 15
minutes.
C) Continuous indirect
integrity monitoring must be separately conducted on each membrane
unit.
D) If continuous indirect
integrity monitoring includes turbidity and if the filtrate turbidity readings
are above 0.15 NTU for a period greater than 15 minutes (i.e., two consecutive
15-minute readings above 0.15 NTU), direct integrity testing must immediately
be performed on the associated membrane unit, as specified in subsections
(b)(3)(A) through (b)(3)(E).
E) If
indirect integrity monitoring includes an Agency-approved alternative parameter
and if the alternative parameter exceeds an Agency-approved control limit for a
period greater than 15 minutes, direct integrity testing must immediately be
performed on the associated membrane units, as specified in subsections
(b)(3)(A) through (b)(3)(E).
c) Second Stage Filtration. A supplier
receives 0.5-log Cryptosporidium treatment credit for a separate second stage
of filtration that consists of sand, dual media, GAC, or other fine grain media
following granular media filtration if the Agency approves by a SEP. To be
eligible for this credit, the first stage of filtration must be preceded by a
coagulation step and both filtration stages must treat the entire plant flow
taken from a surface water or groundwater under the direct influence of surface
water source. A cap, such as GAC, on a single stage of filtration is not
eligible for this credit. The Agency must approve the treatment credit based on
an assessment of the design characteristics of the filtration
process.
d) Slow Sand Filtration
(as secondary filter). A supplier is eligible to receive 2.5-log
Cryptosporidium treatment credit by a SEP for a slow sand filtration process
that follows a separate stage of filtration if both filtration stages treat
entire plant flow taken from a surface water or groundwater under the direct
influence of surface water source and no disinfectant residual is present in
the influent water to the slow sand filtration process. The Agency must approve
the treatment credit based on an assessment of the design characteristics of
the filtration process. This subsection (d) does not apply to treatment credit
awarded to slow sand filtration used as a primary filtration process.
BOARD NOTE: Derived from
40 CFR
141.719.
