18 AAC 80.650. Filtration

(a) Failure to meet a requirement of this section after the applicable date specified in this subsection is a treatment technique violation. The owner or operator of a Class A or Class B public water system using a surface water source or a GWUDISW source shall install filtration and provide filtration treatment as specified in this section, and disinfection treatment as specified in 18 AAC 80.635(c) and 18 AAC 80.645, within the following periods:

(1) if the department or EPA has determined, in writing, that filtration is required, by the date set by EPA in its determination, or within 18 months after a determination by the department; or

(2) for a system that fails to meet a requirement of 18 AAC 80.620(a) - (d), within 18 months after the failure occurs.

(b) For a system using conventional filtration or direct filtration,

(1) the turbidity level of representative samples of a system's filtered water must be less than or equal to 0.5 NTU in at least 95 percent of the measurements reported each month, measured as specified in 18 AAC 80.340(d) (1) and 18 AAC 80.665(b) ;

(2) if the department finds that the system is capable of achieving at least 99.9 percent removal or inactivation of Giardia lamblia cysts at a turbidity level higher than 0.5 NTU in at least 95 percent of the measurements taken each month, the department will substitute that higher turbidity level for that system; however, the department will not approve a turbidity level that allows more than one NTU in more than five percent of the samples taken each month, measured as specified in 18 AAC 80.340(d) (1) and 18 AAC 80.665(b) ;

(3) the turbidity level of representative samples of a system's filtered water may not exceed five NTUs, measured as specified in 18 AAC 80.340(d) (1) and 18 AAC 80.665(b) ;

(4) upon written request, the department will determine whether to allow turbidity levels of up to one NTU on a case-by-case basis; requests must include sufficient information to allow a determination in accordance with standard sanitary engineering practices and principles; and

(5) notwithstanding 18 AAC 80.010(a) (15)(D), adopting by reference 40 C.F.R. 141.173 (Filtration), a public water system that serves 10,000 or more individuals has until January 1, 2002 to comply with the turbidity requirements of 40 C.F.R. 141.173(a), as adopted by reference in 18 AAC 80.010(a) (15)(D).

(c) For a system using slow sand filtration, the turbidity level of representative samples of a system's filtered water must be less than or equal to one NTU in at least 95 percent of the measurements reported each month, measured as specified in 18 AAC 80.340(d) (1) and 18 AAC 80.665(b) . If the department finds that a higher turbidity level does not cause significant interference with disinfection, the department will substitute that higher turbidity level for that system. However, the turbidity level of representative samples of a system's filtered water may not exceed five NTUs, measured as specified in 18 AAC 80.340(d) (1) and 18 AAC 80.665(b) . Upon written request, the department will determine whether to allow turbidity levels of up to five NTUs on a case-by-case basis and in accordance with standard sanitary engineering principles and practices. A request must include enough information to allow a determination in accordance with standard sanitary engineering principles and practices.

(d) For a system using diatomaceous earth filtration, the turbidity level of representative samples of the system's filtered water must be less than or equal to one NTU in at least 95 percent of the measurements reported each month, measured as specified in 18 AAC 80.340(d) (1) and 18 AAC 80.665(b) . However, the turbidity level of representative samples of the system's filtered water may not exceed five NTUs, measured as specified in 18 AAC 80.340(d) (1) and 18 AAC 80.665(b) .

(e) The owner or operator may use a filtration technology not listed in (b) - (d) of this section if the owner or operator demonstrates to the department, using a pilot plant study or a full-scale study, or in accordance with standard sanitary engineering practices and principles, that the alternative filtration technology, in combination with disinfection treatment that meets the requirements of 18 AAC 80.635(c) and 18 AAC 80.645, consistently achieves 99.9 percent removal and inactivation of Giardia lamblia cysts and 99.99 percent removal and inactivation of viruses. For a system that makes this demonstration and obtains approval to use an alternate filtration system, the requirements of (c) of this section apply.

(f) Notwithstanding 18 AAC 80.010(a) (15)(D), adopting by reference 40 C.F.R. 141.173 (Filtration), a public water system that serves 10,000 or more individuals has until January 1, 2002 to comply with the requirements set out for other filtration technologies in 40 C.F.R. 141.173(b), as adopted by reference in 18 AAC 80.010(a) (15)(D).

History: Eff. 10/1/99, Register 151; am 9/28/2001, Register 159; am 1/11/2006, Register 177

Authority: AS 46.03.020

Editor's note: Guidance on standard sanitary engineering practices and principles, as addressed in 18 AAC 80.650(b) -(c), may be found in the department's Alaska Water Treatment Guidance Manual, and in EPA's Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources . Guidance on standard sanitary engineering practices and principles, as addressed in 18 AAC 80.650(e) , may be found in State Alternative Technology Approval Protocol, by the Association of State Drinking Water Administrators. Information about how to review or obtain these documents is in the editor's note to 18 AAC 80.010.

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