UV Dose for Potable Water
Required UV-C dose 40 mJ/cm² at 254 nm per WHO drinking-water guideline for log-4 viral inactivation.
Applied UV dose
5mJ/cm²
Status
Below 40 mJ/cm² - increase UV power or reduce flow
Formula, assumptions, and limits
Rough order-of-magnitude estimate; real UV reactors use bio-dosimetry (NSF 55, USEPA UVDGM). 40 mJ/cm² is the accepted threshold for log-4 inactivation of rotavirus. Post-UV chlorination (0.2 mg/L) provides residual protection in tanks.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Lamp UV-C output | W | lamp spec | |
| Reactor volume | m³ | reactor spec | |
| UV transmittance at 254 nm | - | UVT sensor |