Panthogen(s) to be inactivated
Different pathogens require different amounts of UV energy to inactivate them. Therefore for any UV system, it must be clear which pathogens are to be inactivated. The table below is taken from the USEPA UV Disinfection Guidance Manual (UVDGM) and shows the UV dose required to achieve different log removals of pathogens.
For example to achieve 99% removal (log 2) removal of Cryptosporidium requires 5.8 mJ/cm2. To achieve 4-log removal (99.99% removal) requires 22 mJ/cm2. It is important to note that the relationship between the dose and the log removal, the so called dose response, is not linear. It takes a very much higher dose to achieve log-4 removal compared to log-2 removal.
UV dose requirements in mJ/cm2 to achieve stated log reductions for some typical water-borne pathogens.
Graham Smith. Fluidquip Australia Pty Ltd.