Section 327IAC8-2.6-3. Enhanced filtration

   By December 31, 2001, Subpart H systems serving a population of at least ten thousand (10,000) individuals and, beginning January 1, 2005, Subpart H systems serving a population of fewer than ten thousand (10,000) individuals shall provide treatment consisting of both disinfection, as specified in 327 IAC 8-2-8.6, and filtration treatment that complies with the following:

(1) Requirements for systems using conventional filtration or direct filtration are as follows:

(A) For Subpart H systems using conventional filtration or direct filtration, the turbidity level of representative samples of the system’s filtered water must be less than or equal to three-tenths (0.3) nephelometric turbidity unit in at least ninety-five percent (95%) of the measurements taken each month, measured as specified in 327 IAC 8-2-8.7 and 327 IAC 8-2-8.8.

(B) The turbidity level of representative samples of the system’s filtered water must at no time exceed one (1) nephelometric turbidity unit, measured as specified in 327 IAC 8-2-8.7 and 327 IAC 8-2-8.8.

(C) A system that uses lime softening may acidify representative samples prior to analysis using a protocol approved by the commissioner.

(2) A Subpart H system may use filtration technologies other than:

(A) conventional filtration treatment;

(B) direct filtration;

(C) slow sand filtration; or

(D) diatomaceous earth filtration;

if it demonstrates to the commissioner, using pilot plant studies or other means, that the alternative filtration technology, in combination with disinfection treatment that meets the requirements of 327 IAC 8-2-8.6, consistently achieves ninety-nine and nine-tenths percent (99.9%) removal or inactivation of Giardia lamblia cysts and ninety-nine and ninety-nine hundredths percent (99.99%) removal or inactivation of viruses, and ninety-nine percent (99%) removal of Cryptosporidium oocysts, and the commissioner approves the use of the filtration technology.

(3) For each approval under subdivision (2), the commissioner will set turbidity performance requirements that the system must meet at least ninety-five percent (95%) of the time (not to exceed 1 NTU) and that the system may not exceed at any time at a level that consistently achieves ninety-nine and nine-tenths percent (99.9%) removal or inactivation of Giardia lamblia cysts, ninety-nine and ninety-nine hundredths percent (99.99%) removal or inactivation of viruses, and ninety-nine percent (99%) removal of Cryptosporidium oocysts (not to exceed 5 NTU).

(Water Pollution Control Division; 327 IAC 8-2.6-3; filed May 1, 2003, 12:00 p.m.: 26 IR 2857; filed Jun 13, 2005, 2:30 p.m.: 28 IR 3252)