40 CFR §141.534
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Use the tables in § 141.74(b)(3)(v) to determine the appropriate CT99.9 value. Calculate the total inactivation ratio as follows, and multiply the value by 3.0 to determine log inactivation of Giardia lamblia: