Disinfection CT (USEPA SWTR)
CT achieved (C * t10) compared to USEPA SWTR Guidance Manual required CT for 3-log Giardia inactivation by temperature and pH. Bundled <= 0.4 mg/L free-chlorine table; state primacy agency table governs final compliance.
Formula and source
CT_achieved (mg-min/L) = chlorine_mg_l * t10_minutes. CT_required from bilinear interpolation of SWTR Table A-1 (free chlorine, 3-log Giardia, <=0.4 mg/L band) over the 6 temperature x 4 pH grid. 4-log virus credit from the SWTR Table E-1 simplified contact-time relation.
USEPA Surface Water Treatment Rule Guidance Manual EPA 815-R-99-014, Tables A-1 and E-1 (public domain).
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