R 325.10611b Filtration and disinfection; filtration.

Rule 611b. (1) Subpart H supplies shall comply with all of the following filtration requirements, as applicable: For a supply using... (i) The turbidity level of representative samples of a supply's filtered water shall at no time exceed... (ii) Not less than 95% of the measurements taken each month shall be less than or equal to... (a) Conventional, direct, or membrane filtration 1 ntu 0.3 ntu (b) Slow sand or diatomaceous earth filtration 5 ntu 1 ntu (c) An alternative filtration technology approved by the department, based on the demonstration described in subrule (3) of this rule. The department-set turbidity level, not to exceed 5 ntu, based on the demonstration described in subrule (3) of this rule. The department-set turbidity level, not to exceed 1 ntu, based on the demonstration described in subrule (3) of this rule. (2) A supply using lime softening, where the final pH exceeds 8.3, may acidify representative samples before turbidity analysis using a protocol approved by the department. The approved protocol shall require the use of a concentrated acid in sufficient quantities to lower the pH to less than 8.3, dissolve only calcium carbonate and magnesium hydroxide, and not to dilute the representative sample. (3) A public water supply may use a filtration technology not listed in subrule (1)(a) or (b) of this rule if the supply demonstrates to the department, using pilot plant studies or other means, that the alternative filtration technology, in combination with disinfection treatment that meets the requirements of R 325.10611a(2), consistently achieves the removal or inactivation percentages in R 325.10611(3), and the department approves the use of the filtration technology. For each approval, the department will set turbidity performance requirements that the supply shall meet not less than 95% of the time and the supply shall not exceed, at any time, at a level in subrule (1)(c) of this rule that consistently achieves the removal or inactivation percentages in R 325.10611(3).