I note water is to be used for drinking, not lab work, therefore need not
be sterile, only safe, ie free of pathogens. Bacteria such as Salmonella
etc. can be killed by UV exposure. Other pathogens eg. cysts of
Cryptosporidia, Giardia, are far more resistant. Good ways of ensuring
low/absent levels of these parasitic pathogens in water are boiling, ozone
treatment &/or filtration. Chlorine levels in commercial water supplies
can not guarantee eradication of these parasites.
I was involved in an investigation of campylobacter/cryptosporidium
infection caused by contaminated spring water where UV disinfection system
was in place ( In Epidemiology and Infection ( 1996) vol 116, pages
303-308. A mixed outbreak of cryptosporidium and campylobacter infection
associated with a private water supply ). One of the problems here was
that the quartz UV housing had been overgrown by biofilm-producing
bacteria, drastically reducing efficiency. I think it is a bad idea to
rely on UV to disinfect a spring source, which should be clean to start
with. It would be wiser to ensure that no contamination, microbiological
or chemical, of the supply occurs between the source and consumption, eg
by sewage or other effluent.
Best wishes
David Jenkins
drsiencyns at aol.com
