Reclaimed water must meet the minimum technology-based treatment methods and treatment reliability standards in WAC 173-219-350 before distribution and use. Reclaimed water must also meet the applicable performance standards established in Table 1 and Table 2 under WAC 173-219-330. Source water for the reclaimed water facility must meet or exceed minimum secondary treatment requirements in WAC 173-221-040 to satisfy the biological oxidation performance standards in this chapter. Raw source water must meet these standards through the reclaimed water treatment process.

(1) Allowable treatment methods for Class B reclaimed water. Class B reclaimed water must also meet the following treatment process train requirements: Biological oxidation followed by disinfection.

(2) Allowable treatment methods for Class A reclaimed water. Class A reclaimed water must also meet one of the following treatment process train requirements:

(a) Biological oxidation, followed by coagulation, filtration, and disinfection, demonstrating at least a 4-log virus removal or inactivation.

(b) Biological oxidation, followed by membrane filtration and disinfection, demonstrating at least a 4-log virus removal or inactivation.

(c) Combination of biological oxidation and membrane filtration via a membrane bioreactor, followed by disinfection, demonstrating at least a 4-log virus removal or inactivation.

(d) An alternative treatment method, that demonstrates to the satisfaction of the lead agency that it provides for equivalent treatment and reliability.

Minimum performance standards for an equivalent process or treatment must demonstrate assurance that reclaimed water quality limits are consistently achieved through proper design, operation, and maintenance of each of the treatment units in the proposed alternative treatment process.

(3) Class A+ reclaimed water. Class A+ reclaimed water requirements must be established by health, on a case-by-case basis, and must have approval of the state board of health before it can be beneficially used for direct potable reuse.