Section 611.1019  Requirements for Microbial Toolbox Components:  Additional Filtration Toolbox Components

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 (C_f) – Log₁₀ (C_p)

Where:

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 (LRV_filter) 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 LRV_filter 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 10^th percentile of the set of LRV_filter 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 10^th 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:

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 (C_f) – Log₁₀ (C_p)

Where:

F)         The removal efficiency of a membrane filtration process demonstrated during challenge testing must be expressed as a log removal value (LRV_C-Test).  If fewer than 20 modules are tested, then LRV_C-Test is equal to the lowest of the representative LRVs among the modules tested. If 20 or more modules are tested, then LRV_C-Test is equal to the 10^th 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 10^th 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:

Where:

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:

LRV_DIT = Log₁₀ (C_f) - Log₁₀ (C_p)

Where:

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.

(Source:  Amended at 44 Ill. Reg. 6996, effective April 17, 2020)