Section 327IAC8-2.6-19. Additional filtration toolbox components; requirements for microbial toolbox components; enhanced treatment for Cryptosporidium

   (a) A PWS using additional filtration toolbox components may receive Cryptosporidium treatment credit of up to 2.0-log for individual bag or cartridge filters and up to 2.5-log credit for bag or cartridge filters operated in series if the PWS complies with the following:

(1) The PWS shall report to the commissioner the results of challenge testing that meets the requirements of subdivision (3)(B) through (3)(I).

(2) The filters must treat the entire plant flow taken from a Subpart H system source.

(3) The PWS shall meet the following criteria:

(A) The Cryptosporidium treatment credit awarded to bag or cartridge filters must be based on the removal efficiency demonstrated during challenge testing that meets the following:

(i) Challenge testing is conducted according to clauses (B) through (I).

(ii) A factor of safety equal to:

(AA) 1-log for individual bag or cartridge filters; and

(BB) 0.5-log for bag or cartridge filters in series;

must be applied to challenge testing results to determine removal credit.

(iii) A PWS may use challenge testing results conducted prior to January 5, 2006, if the prior testing was consistent with the criteria specified under clauses (B) through (I).

(B) Challenge testing must be performed according to the following:

(i) 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 housing the PWS will use for removal of Cryptosporidium.

(ii) Bag or cartridge filters must be challenge tested in the same configuration that the PWS will use, either as individual filters or as a series configuration of filters.

(C) Challenge testing must be conducted using Cryptosporidium or a surrogate, either of which are referred to during challenge testing as the challenge particulate, according to the following:

(i) A surrogate, if used, must be a microorganism that is removed not more efficiently than Cryptosporidium.

(ii) 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.

(iii) Gross measurements, such as turbidity, may not be used.

(D) The maximum feed water concentration that may be used during a challenge test must be based on the detection limit of the challenge particulate in the filtrate (filtrate detection limit) and must be calculated using the following equation:

Maximum Feed Concentration = 1 × 10⁴ × (Filtrate Detection Limit)

(E) Challenge testing must be conducted at the maximum design flow rate for the filter as specified by the manufacturer.

(F) Each filter evaluated must be tested for a duration sufficient to reach one hundred percent (100%) of the terminal pressure drop in order to establish the maximum pressure drop under which the filter can be used to comply with the requirements of sections 7 through 18 of this rule, this section, and sections 20 through 22 of this rule.

(G) 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:	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 C_p must be set equal to the detection limit.

(H) Each filter tested must be challenged with the challenge particulate during three (3) periods over the filtration cycle, as follows:

(i) Within the first two (2) hours of start-up of a new filter.

(ii) When the pressure drop is between forty-five percent (45%) and fifty-five percent (55%) of the terminal pressure drop.

(iii) At the end of the cycle after the pressure drop has reached one hundred percent (100%).

An LRV must be calculated for each of the challenge periods listed under items (i) and (ii) for each filter tested. The LRV for the filter (LRV_filter) must be assigned the value of the minimum LRV observed during the three (3) challenge periods for that filter.

(I) Overall removal efficiency for the filter product line shall be established as follows:

(i) If fewer than twenty (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.

(ii) If twenty (20) or more filters are tested, the following apply:

(AA) Overall removal efficiency for the filter product line must be set equal to the tenth percentile of the set of LRV_filter values for the various filters tested.

(BB) The percentile is defined by (i/(n+1)) where i is the rank of n individual data points ordered lowest to highest.

(CC) If necessary, the tenth percentile may be calculated using linear interpolation.

(J) 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:

(i) conducted; and

(ii) submitted to the commissioner.

  (b) The following requirements apply to the use of membrane filtration for Cryptosporidium treatment credit:

(1) A PWS may receive Cryptosporidium treatment credit for membrane filtration according to the following:

(A) The PWS meets the criteria of this subsection.

(B) Membrane cartridge filters that meet the definition of membrane filtration in 327 IAC 8-2-1 are eligible for this credit.

(C) The level of treatment credit a PWS receives is equal to the lower of the values determined under the following:

(i) The removal efficiency demonstrated during challenge testing conducted under subdivision (2).

(ii) The maximum removal efficiency that can be verified through direct integrity testing used with the membrane filtration process under the conditions in subdivision (3).

(2) The PWS shall comply with the following regarding challenge testing in order to be eligible for Cryptosporidium treatment credit:

(A) Conduct challenge testing on the membrane used by the PWS to evaluate removal efficiency.

(B) Report the results of challenge testing to the commissioner.

(C) A PWS may use data from challenge testing conducted prior to January 5, 2006, if the prior testing was consistent with the criteria under clause (D).

(D) Challenge testing must be conducted according to the following criteria:

(i) Challenge testing must be conducted on either a:

(AA) full-scale membrane module that is identical in material and construction to the membrane modules used in the PWS's treatment facility; or

(BB) smaller-scale membrane module that is 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.

(ii) Challenge testing must be conducted using Cryptosporidium oocysts or a surrogate either of which are referred to during challenge testing as the challenge particulate, according to the following:

(AA) A surrogate, if used, must be a microorganism that is removed not more efficiently than Cryptosporidium oocysts.

(BB) 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.

(CC) Gross measurements, such as turbidity, may not be used.

(iii) The maximum feed water concentration that may 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 × 10⁶ × (Filtrate Detection Limit)

(iv) 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, where:

(AA) flux is defined as the throughput of a pressure driven membrane process expressed as flow per unit of membrane area; and

(BB) 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 like backwashing.

(v) 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:	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 C_p must be 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.

(vi) The overall removal efficiency of a membrane filtration process demonstrated during challenge testing must be expressed as a log removal value (LRV_C-Test) and established according to the following:

(AA) If fewer than twenty (20) modules are tested, then LRV_C-Test is equal to the lowest of the representative LRVs among the modules tested.

(BB) If twenty (20) or more modules are tested, then LRV_C-Test is equal to the tenth 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 tenth percentile can be calculated using linear interpolation.

(vii) The PWS shall establish a quality control release value (QCRV) according to the following:

(AA) The challenge test must establish a QCRV for a nondestructive performance test that demonstrates the Cryptosporidium removal capability of the membrane filtration module.

(BB) The performance test must be applied to each production membrane module used by the system that was not directly challenge tested in order to verify Cryptosporidium removal capability.

(CC) Production modules that do not meet the established QCRV are not eligible for the treatment credit demonstrated during the challenge test.

(viii) If a previously tested membrane is modified in a manner that could change the removal efficiency of the membrane or the applicability of the nondestructive 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 commissioner.

(3) A PWS shall conduct direct integrity testing that meets the following criteria:

(A) For the purpose of this section, a direct integrity test is defined as a physical test applied to a membrane unit in order to identify and isolate integrity breaches, for example, one (1) or more leaks that could result in contamination of the filtrate.

(B) Direct integrity testing must be conducted in a manner that demonstrates a removal efficiency equal to or greater than the removal credit awarded to the membrane filtration process.

(C) Direct integrity testing must meet the following requirements:

(i) 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 system for the purpose of integrity testing or other maintenance.

(ii) The direct integrity method must have a resolution of at least three (3) micrometers (µm) or less, where resolution is defined as the size of the smallest integrity breach that contributes to a response from the direct integrity test.

(iii) The direct integrity test must have a sensitivity sufficient to verify the log treatment credit awarded to the membrane filtration process by the commissioner, 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 approach in either of the following, as applicable to the type of direct integrity test the system uses:

(AA) For direct integrity tests that use an applied pressure or vacuum, the direct integrity test sensitivity must be calculated according to the following equation:

LRV_DIT = LOG₁₀ (Q_p/(VCF X Q_breach))

Where:	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 suspended solids concentration on the high pressure side of the membrane relative to that in the feed water.

(BB) For direct integrity tests that use 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:	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

(iv) A PWS shall 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 commissioner.

(v) If the result of a direct integrity test exceeds the control limit established under item (iv), the PWS:

(AA) shall remove the membrane unit from service;

(BB) shall conduct a direct integrity test to verify any repairs; and

(CC) may return the unit to service only if the direct integrity test is within the established control limit.

(vi) A PWS shall 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 commissioner may approve less frequent direct integrity testing based on:

(AA) demonstrated process reliability;

(BB) the use of multiple barriers effective for Cryptosporidium; or

(CC) reliable process safeguards.

(4) A PWS shall conduct continuous indirect integrity monitoring that meets the following criteria:

(A) For the purpose of this section, indirect integrity monitoring is defined as monitoring some aspect of filtrate water quality that is indicative of the removal of particulate matter.

(B) A PWS that implements continuous direct integrity testing of membrane units in accordance with the criteria under subdivision (3)(C)(i) through (3)(C)(v) is not subject to the requirements of this subdivision for continuous indirect integrity monitoring.

(C) A PWS shall submit a monthly report to the commissioner that includes the following:

(i) A summary of all continuous indirect integrity monitoring results triggering direct integrity testing.

(ii) The corrective action that was taken in each case that direct integrity testing was triggered.

(D) Continuous indirect integrity monitoring must be conducted on each membrane unit according to the following criteria:

(i) Unless the commissioner approves an alternative parameter, continuous indirect integrity monitoring must include continuous filtrate turbidity monitoring.

(ii) Continuous monitoring must be conducted at a frequency of not less than once every fifteen (15) minutes.

(iii) Continuous monitoring must be separately conducted on each membrane unit.

(iv) If indirect integrity monitoring includes turbidity and if the filtrate turbidity readings are above fifteen-hundredths (0.15) NTU for a period greater than fifteen (15) minutes (for example, two (2) consecutive fifteen (15) minute readings are above fifteen-hundredths (0.15) NTU), direct integrity testing must immediately be performed on the associated membrane unit as specified under subdivision (3)(C)(i) through (3)(C)(v).

(v) If indirect integrity monitoring includes an alternative parameter approved by the commissioner under item (i) and if the alternative parameter exceeds the control limit approved by the commissioner for a period greater than fifteen (15) minutes, direct integrity testing must immediately be performed on the associated membrane units as specified under subdivision (3)(C)(i) through (3)(C)(v).

  (c) A PWS may receive 0.5-log Cryptosporidium treatment credit for a separate second stage of filtration if the following are met:

(1) The separate second stage of filtration must consist of:

(A) sand;

(B) dual media;

(C) granular activated carbon (GAC); or

(D) other fine grain media;

following granular media filtration if the commissioner approves.

(2) To be eligible for this credit, the PWS shall meet the following:

(A) The first stage of filtration must be preceded by a coagulation step.

(B) Both filtration stages must treat the entire plant flow taken from a:

(i) surface water source; or

(ii) ground water under the direct influence of surface water source.

(3) A cap, for example, a cap comprised of GAC, on a single stage of filtration is not eligible for this credit.

(4) The commissioner shall approve the treatment credit based on an assessment of the design characteristics of the filtration process.

  (d) A PWS may receive 2.5-log Cryptosporidium treatment credit for a slow sand filtration process that follows a separate stage of filtration if the following are met:

(1) Both filtration stages must treat the entire plant flow taken from a:

(A) surface water source; or

(B) ground water under the direct influence of surface water source.

(2) No disinfectant residual is present in the influent water of the slow sand filtration process.

(3) This treatment credit is not available where treatment credit is awarded to slow sand filtration used as a primary treatment process.

(4) The commissioner shall approve the treatment credit based on an assessment of the design characteristics of the filtration process.

(Water Pollution Control Division; 327 IAC 8-2.6-19; filed May 7, 2010, 9:30 a.m.: 20100602-IR-327080198FRA)