Michigan Administrative Code › Department - Environmental Quality › Drinking Water And Municipal Assistance Division › Supplying Water to the Public › Part 6 - STATE DRINKING WATER STANDARDS AND ANALYTICAL › Section R. 325.10611l - Enhanced treatment for Cryptosporidium; microbial toolbox; additional filtration toolbox components

Current through Vol. 24-12, July 15, 2024
Rule 611l.
(1) Bag
				  and cartridge filters is an additional filtration toolbox component. Subpart H
				  supplies that are subject to R 325.10611d 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. To be eligible for
				  this credit, supplies shall report the results of challenge testing that meets
				  the requirements of subdivisions (b) to (i) of this subrule to the department.
				  The filters shall treat the entire plant flow taken from a surface water or
				  GWUDI source. All of the following apply to bag and cartridge filters as an
				  additional filtration toolbox component:
(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 subdivisions (b) to (i) of this
				  subrule. 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. Subpart H supplies may
				  use results from challenge testing conducted before January 5, 2006 if the
				  prior testing was consistent with the criteria specified in subdivisions (b) to
				  (i) of this subrule.
(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 supply will use for removal of
				  Cryptosporidium. Bag or cartridge filters shall be challenge tested in the same
				  configuration that the supply 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, that is filtrate detection limit,
				  and shall be calculated using the following equation:
Maximum Feed Concentration = 1 x 10[superscript]4 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 R 325.10611d to R
				  325.10611n and R 325.10720b to R 325.10720e.
(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 all of the following periods over the
				  filtration cycle:
(i) Within 2 hours of
				  start-up of a new filter.
(ii) When
				  the pressure drop is between 45 and 55% of the terminal pressure
				  drop.
(iii) At the end of the cycle
				  after the pressure drop has reached 100% of the terminal pressure drop. Note to
				  subdivision (h) of this subule: 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.
(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.
(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.