Ozone Dosing & CT Screening

Methodology

CT compliance follows the official US EPA Long Term 2 Enhanced Surface Water Treatment Rule (40 CFR §141.720(b)(2)) Cryptosporidium ozone CT table, evaluated via its own sanctioned continuous equation — Log credit = (0.0397 × 1.09757^Temp) × CT — which reproduces the published table exactly at every tabulated temperature. T10 is computed as hydraulic retention time (contact volume ÷ flow) times a baffling factor from the standard EPA/AWWA contact-basin classification (0.1 unbaffled to 0.7 superior).

Theoretical ozone rate (g/h) equals flow (m³/h) times target applied dose (mg/L) — dimensionally exact, since 1 mg/L applied across 1 m³/h is 1 gram of ozone per hour. Required generator output divides that rate by the transfer efficiency of the injection/contact system, since not all generated ozone dissolves into the water — typical well-designed systems achieve 85-95%, and this should be confirmed against actual equipment performance.

Standards / Reference Basis

Assumptions

• CT is estimated as hydraulic retention time multiplied by a generic baffling factor.
• The screening uses the entered water temperature, baffling factor, and residual.

Scope / Limitations

• This is a preliminary CT screen; generic baffling is not a regulatory compliance basis.
• No approved contact-time/residual basis is included, so the screen cannot determine regulatory compliance.