NR 810.45(1)(b)(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.

NR 810.45(1)(c)(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.

NR 810.45(1)(d)(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:

NR 810.45(1)(e)(e) Challenge testing shall be conducted at the maximum design flow rate for the filter as specified by the manufacturer.

NR 810.45(1)(f)(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.

NR 810.45(1)(g)(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 = 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.

NR 810.45(1)(h)(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 (LRVfilter) shall be assigned the value of the minimum LRV observed during the 3 challenge periods for that filter.

NR 810.45(1)(i)(i) If fewer than 20 filters are tested, the overall removal efficiency for the filter product line shall 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 shall 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.

NR 810.45(1)(j)(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.

NR 810.45(2)(a)(a) Definitions. In this subsection:

NR 810.45(2)(a)1.1. “Flux” means the throughput of a pressure driven membrane process expressed as flow per unit of membrane area.

NR 810.45(2)(a)2.2. “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.

NR 810.45(2)(a)3.3. “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.

NR 810.45(2)(b)(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:

NR 810.45(2)(b)1.1. The removal efficiency demonstrated during challenge testing conducted under the conditions in par. (b).

NR 810.45(2)(b)2.2. The maximum removal efficiency that can be verified through direct integrity testing used with the membrane filtration process under the conditions in par. (c).

NR 810.45(2)(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:

NR 810.45(2)(c)1.1. 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.

NR 810.45(2)(c)2.2. 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.

NR 810.45(2)(c)3.3. 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:

NR 810.45(2)(c)4.4. 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.

NR 810.45(2)(c)5.5. 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: