Interactive Calculator · 2026
UV Dose Calculator
Work out the UV dose delivered during disinfection and check it against your reuse target. Enter the UV intensity and exposure time — get the delivered dose in mJ/cm² and see, at a glance, whether it clears the target.
Delivered dose (intensity × time) vs reuse target
Your UV system
Irradiance at the water surface — lamp output net of quartz-sleeve and water losses.
Residence time in the UV contact chamber.
Reuse target — commonly ≈40 mJ/cm² for treated water.
Delivered dose vs target
Pass — delivering 50 mJ/cm² against a 40 mJ/cm² target (25% margin).
UV dose (fluence) is simply the UV intensity multiplied by how long the water is exposed. Push either higher and the dose rises in step.
A positive margin means you clear the reuse target with headroom for lamp ageing and fouling; a negative one means you need more intensity, longer contact time, or a lower flow.
How this is calculated
- Delivered dose = intensity × time = 25 × 2 = 50 mJ/cm².
- Margin vs target = (dose ÷ target − 1) × 100 = (50 ÷ 40 − 1) × 100 = 25%.
- Result = dose ≥ target, so this run meets the 40 mJ/cm² reuse target.
Indicative check for concept planning. A validated UV reactor also accounts for UV transmittance, flow distribution, lamp fouling and end-of-life output — confirm with a qualified consultant before procurement.
Related Guides — Deep-dive reading
Chlorination System in an STP: Disinfection Explained
The final disinfection step that kills the pathogens biology and filtration leave behind — how chlorine dosing, contact time and residual work together to make treated sewage safe to reuse or discharge, explained for owners and operators alike.
Sewage Treatment PlantsThe Sewage Treatment Process Flow, Explained: Every Stage From Inlet to Reuse
Follow a drop of sewage through a typical STP — inlet, screening, aeration, clarifier, filtration, disinfection and reuse — as one connected flow, with a block diagram and a unit-by-unit table, in plain language.
Sewage Treatment PlantsOzonation in STPs: Ozone Disinfection, Colour and Odour Removal Explained
How ozone works as a tertiary treatment step in advanced sewage treatment plants, how it compares with chlorine and UV, where it earns its place, and where it does not — written for engineers and informed building owners.
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