WAC 246-290-676   Filtration technology and design criteria.  (1) General.

     (a) The purveyor proposing to construct new water treatment facilities or to make additions to existing water treatment facilities for surface and GWI sources shall ensure that the facilities comply with the treatment, design, and reliability requirements of Part 6 of chapter 246-290 WAC.

     (b) The purveyor shall submit an engineering report to the department describing how the treatment facilities will be designed to comply with the requirements specified in Subparts A, B, and C of Part 6 of chapter 246-290 WAC.

     (2) Filtration technology.

     (a) The purveyor shall select a filtration technology acceptable to the department using criteria such as those outlined in department guidance on surface water treatment. The following filtration technologies are considered acceptable:

     (i) Conventional;

     (ii) Direct;

     (iii) Diatomaceous earth; and

     (iv) Slow sand.

     (b) In addition to the technologies specified in subsection (2)(a) of this section, alternative filtration technologies may be acceptable, if the purveyor demonstrates to the department's satisfaction all of the following:

     (i) Through acceptable third party testing, that system components do not leach or otherwise add substances to the finished water that would violate drinking water standards, or otherwise pose a threat to public health;

     (ii) The technology's effectiveness in achieving at least 99 percent (2 log) removal of Giardia lamblia cysts or cyst surrogate particles, and at least 99 percent (2 log) removal of Cryptosporidium oocysts or oocyst surrogate particles. The purveyor shall further demonstrate the technology's removal capability through research conducted:

     (A) By a party acceptable to the department; and

     (B) In accordance with protocol and standards acceptable to the department.

     (iii) Through on-site pilot plant studies or other means, that the filtration technology:

     (A) In combination with disinfection treatment consistently achieves 99.9 percent (3 log) removal and inactivation of Giardia lamblia cysts and 99.99 percent (4 log) removal and inactivation of viruses; and

     (B) Meets the applicable turbidity performance requirements as determined by the department for the specific treatment process being considered, but in no case to exceed 1.0 NTU for the finished water.

     (3) Pilot studies.

     (a) The purveyor shall ensure pilot studies are conducted for all proposed filtration facilities, except where waived based on engineering justification acceptable to the department.

     (b) The purveyor shall obtain department approval for the pilot study plan before the pilot filter is constructed and before the pilot study is undertaken.

     (c) The pilot study plan shall identify at a minimum:

     (i) Pilot filter design;

     (ii) Water quality and operational parameters to be monitored;

     (iii) Type of data to be collected, frequency of data collection, and length of pilot study; and

     (iv) Pilot plant operator qualifications.         

     (d) The purveyor shall ensure that the pilot study is:

     (i) Conducted to simulate proposed full-scale design conditions;

     (ii) Conducted over a time period that will demonstrate the effectiveness and reliability of the proposed treatment system during changes in seasonal and climatic conditions; and

     (iii) Designed and operated in accordance with good engineering practices and that ANSI/NSF standards 60 and 61 are considered.

     (e) When the pilot study is complete, the purveyor shall submit a project report to the department for approval under WAC 246-290-110.

     (4) Design criteria.

     (a) The purveyor shall ensure that water treatment facilities for surface and GWI sources are designed and constructed in accordance with good engineering practices documented in references such as those identified in WAC 246-290-200.

     (b) Filtration facilities.

     (i) The purveyor shall ensure that all new filtration facilities and improvements to any existing filtration facilities (excluding disinfection) are designed to achieve at least 99 percent (2 log) removal of Giardia lamblia cysts, and 99 percent (2 log) removal of Cryptosporidium oocysts; and

     (ii) The purveyor shall ensure that all new filtration facilities contain provisions for filtering to waste with appropriate measures for backflow prevention.

     (c) The purveyor shall ensure that disinfection systems for new filtration facilities or improvements to existing disinfection facilities are designed to meet the requirements of WAC 246-290-662.



[Statutory Authority: RCW 70.119A.180 and 43.20.050. 08-03-061, § 246-290-676, filed 1/14/08, effective 2/14/08. Statutory Authority: RCW 43.20.050 (2) and (3) and70.119A.080 . 03-08-037, § 246-290-676, filed 3/27/03, effective 4/27/03. Statutory Authority: RCW 43.02.050 [43.20.050]. 99-07-021, § 246-290-676, filed 3/9/99, effective 4/9/99. Statutory Authority: RCW 43.20.050. 93-08-011 (Order 352B), § 246-290-676, filed 3/25/93, effective 4/25/93.]