Section NR 810.45 - Additional filtration toolbox components(1) BAG OR CARTRIDGE FILTERS. Public water systems receive 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 in pars. (a) to (j). To be eligible for this credit, water suppliers for systems shall report the results of challenge testing that meets the requirements of pars. (b) to (i) to the department. The filters shall treat the entire plant flow taken from a surface water or GWUDI source. (a) The Cryptosporidium treatment credit awarded to bag or cartridge filters shall be based on the removal efficiency demonstrated during challenge testing that is conducted according to the criteria in pars. (b) to (i). 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 shall be applied to challenge testing results to determine removal credit. Systems may use results from challenge testing conducted prior to January 5, 2006 if the prior testing was consistent with the criteria specified in pars. (b) to (i).(b) Challenge testing shall 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 system will use for removal of Cryptosporidium. Bag or cartridge filters shall be challenge tested in the same configuration that the system will use, either as individual filters or as a series configuration of filters.(c) Challenge testing shall 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 shall 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.(d) The maximum feed water concentration that can be used during a challenge test shall be based on the detection limit of the challenge particulate in the filtrate, including filtrate detection limit, and shall be calculated using the following equation: Maximum Feed Concentration = 1 x 104 x (Filtrate Detection Limit)
(e) Challenge testing shall be conducted at the maximum design flow rate for the filter as specified by the manufacturer.(f) Each filter evaluated shall be tested for a duration sufficient to reach 100% 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 chapter.(g) Removal efficiency of a filter shall 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; and Cp= the filtrate concentration measured during the challenge test. In applying this equation, the same units shall be used for the feed and filtrate concentrations. If the challenge particulate is not detected in the filtrate, then the term Cp shall be set equal to the detection limit.
(h) Each filter tested shall be challenged with the challenge particulate during 3 periods over the filtration cycle: within 2 hours of start-up of a new filter; when the pressure drop is between 45% and 55% of the terminal pressure drop; and at the end of the cycle after the pressure drop has reached 100% of the terminal pressure drop. An LRV shall be calculated for each of these challenge periods for each filter tested. The LRV for the filter (LRV filter) shall be assigned the value of the minimum LRV observed during the 3 challenge periods for that filter.(i) If fewer than 20 filters are tested, the overall removal efficiency for the filter product line shall 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 shall be set equal to the 10th 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 10th 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 shall be conducted and submitted to the department.(2) MEMBRANE FILTRATION. (a)Definitions. In this subsection:1. "Flux" means the throughput of a pressure driven membrane process expressed as flow per unit of membrane area.2. "Module" means the smallest component of a membrane unit in which a specific membrane surface area is housed in a device with a filtrate outlet structure.3. "Recovery" means 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 such as backwashing.(b)Removal credit. Systems receive Cryptosporidium treatment credit for membrane filtration that meets the criteria of this paragraph. Membrane cartridge filters that meet the definition of membrane filtration in s. NR 810.02(27) are eligible for this credit. The level of treatment credit a system receives is equal to the lower of the values determined under the following: 1. The removal efficiency demonstrated during challenge testing conducted under the conditions in par. (b).2. The maximum removal efficiency that can be verified through direct integrity testing used with the membrane filtration process under the conditions in par. (c).(c)Challenge testing. The membrane used by the system shall undergo challenge testing to evaluate removal efficiency, and the water supplier for the system shall report the results of challenge testing to the department. Challenge testing shall be conducted according to the criteria in subds. 1 to 7. Systems may use data from challenge testing conducted prior to January 5, 2006, if the prior testing was consistent with the following criteria: 1. Challenge testing shall be conducted on either a full-scale membrane module, identical in material and construction to the membrane modules used in the system's treatment facility, or a smaller-scale membrane module, identical in material and similar in construction to the full-scale module.2. Challenge testing shall 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, shall 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.3. 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 shall be determined according to the following equation: Maximum Feed Concentration = 3.16 x 106 x (Filtrate Detection Limit)
4. Challenge testing shall be conducted under representative hydraulic conditions at the maximum design flux and maximum design process recovery specified by the manufacturer for the membrane module.5. Removal efficiency of a membrane module shall 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; and Cp= the filtrate concentration measured during the challenge test. Equivalent units shall 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 shall be calculated for each membrane module evaluated during the challenge test.
6. The removal efficiency of a membrane filtration process demonstrated during challenge testing shall 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.7. The challenge test shall 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 shall be applied to each production membrane module used by the system 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.8. 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 shall be conducted and submitted to the department.(d)Direct integrity testing. Systems shall 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 subds. 1. to 6. In this subsection, a direct integrity test means a physical test applied to a membrane unit in order to identify and isolate integrity breaches, including one or more leaks that could result in contamination of the filtrate. 1. The direct integrity test shall 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.2. The direct integrity method shall have a resolution of 3 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.3. The direct integrity test shall have a sensitivity sufficient to verify the log treatment credit awarded to the membrane filtration process by the department, where sensitivity is defined as the maximum log removal value that can be reliably verified by a direct integrity test. Sensitivity shall be determined using the approach in either this subd. 3. a. or b. as applicable to the type of direct integrity test the system uses. a. For direct integrity tests that use an applied pressure or vacuum, the direct integrity test sensitivity shall be calculated according to the following equation: LRVDIT= LOG10(Qp/(VCF x Qbreach))
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, and 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.
b. For direct integrity tests that use a particulate or molecular marker, the direct integrity test sensitivity shall 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; and Cp= the filtrate concentration of the marker from an integral membrane unit.
4. Systems 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 department.5. If the result of a direct integrity test exceeds the control limit established under subd. 4., the system shall remove the membrane unit from service. Systems shall conduct a direct integrity test to verify any repairs, and may return the membrane unit to service only if the direct integrity test is within the established control limit.6. Systems shall conduct direct integrity testing on each membrane unit at a frequency of not less than 3 times each day that the membrane unit is in operation. The department may approve less frequent testing, based on demonstrated process reliability, the use of multiple barriers effective for Cryptosporidium, or reliable process safeguards.(e) Indirect integrity monitoring. Systems shall conduct continuous indirect integrity monitoring on each membrane unit according to the criteria in subds. 1. to 5. In this subsection, indirect integrity monitoring means monitoring some aspect of filtrate water quality that is indicative of the removal of particulate matter. A system that implements continuous direct integrity testing of membrane units in accordance with the criteria in par. (d) 1. to 5. is not subject to the requirements for continuous indirect integrity monitoring. Water suppliers for systems shall submit a monthly report to the department summarizing all continuous indirect integrity monitoring results triggering direct integrity testing and the corrective action that was taken in each case. 1. Unless the department approves an alternative parameter, continuous indirect integrity monitoring shall include continuous filtrate turbidity monitoring.2. Continuous monitoring shall be conducted at a frequency of no less than once every 15 minutes.3. Continuous monitoring shall be separately conducted on each membrane unit.4. If indirect integrity monitoring includes turbidity and if the filtrate turbidity readings are above 0.15 NTU for a period greater than 15 minutes, or 2 consecutive 15-minute readings above 0.15 NTU, direct integrity testing shall immediately be performed on the associated membrane unit as specified in par. (d) 1. to 5.5. If indirect integrity monitoring includes a department-approved alternative parameter and if the alternative parameter exceeds a department-approved control limit for a period greater than 15 minutes, direct integrity testing shall immediately be performed on the associated membrane units as specified in par. (d) 1. to 5.(3) SECOND STAGE FILTRATION. Public water systems receive 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 department approves. To be eligible for this credit, the first stage of filtration shall be preceded by a coagulation step and both filtration stages shall treat the entire plant flow taken from a surface water or GWUDI source. A cap, such as GAC, on a single stage of filtration is not eligible for this credit. The department shall approve the treatment credit based on an assessment of the design characteristics of the filtration process.(4) SLOW SAND FILTRATION AS SECONDARY FILTER. Public water systems are eligible to receive 2.5 -log Cryptosporidium treatment credit 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 GWUDI source and no disinfectant residual is present in the influent water to the slow sand filtration process. The department shall approve the treatment credit based on an assessment of the design characteristics of the filtration process. This subsection does not apply to treatment credit awarded to slow sand filtration used as a primary filtration process.Wis. Admin. Code Department of Natural Resources NR 810.45
CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.