how use ultraviolet light to sterilize?

John P. Hegarty jph10 at psu.edu
Sun Jan 3 00:23:35 EST 1999

I have read papers supporting this claim, indicating a combined thermal and
optical phenomenon. While not ideal, the use of solar heating is a
remarkably effective, low-cost method for water disinfection in equatorial
regions. (Joyce et al. 1996) demonstrated that water contained in 2 liter
transparent bottles, spiked with _E. coli_ and exposed to full Kenyan
sunshine showed no viable bacteria after 7 hours, (or 12 hours later when
removed from sunshine, indicating no bacterial recovery).  A related study
(Conroy et al. 1996) implemented this process in the field and was
associated with a significant reduction in morbidity in communities with no
other means of disinfecting drinking water. This process was further
characterized (McGuigan et al. 1998) showing inactivation effects even in
highly turbid water (200 ntu) and at low irradiances of only 10 mW cm-2.
Thermal inactivation is found to be important only at water temperatures
above 45 degrees C, at which point strong synergy between optical and
thermal inactivation processes is observed. This process would be of
particular use to refugee camps in disaster areas. Quite an inspiring
example of innovative, applied microbiology!

Baker K.H. and J.P. Hegarty (1997) Detection and occurrence of indicator
organisms and pathogens. Water Environment Research. 69(4):406.
Convoy R.M et al.(1996) Solar disinfection  of drinking water and diarrhea
in Maasai children: A controlled field trial. Lancet 348:1695.
Joyce T.M.et al.(1996) Inactivation of fecal bacteria in drinking water by
solar heating. Applied and Environmental Microbiology 62:399.
McGuigan K.G. et al. (1998) Solar disinfection of drinking water contained
in transparent plastic bottles: characterizing the bacterial inactivation
process. Journal of Applied Microbiology Jun;84(6):1138.

- John P. Hegarty, jph10 at psu.edu
  Environmental Microbiology - Penn State
  Helicobacter Research Lab

> Dr. Michael J. Miller wrote in message ...
> Is there any scientific data to support the claim below?

>> In article <3683ED68.E247049A at a-net.net.th>, comfortc at infonews.co.th
>> In Thailand we have easy way to produce bottle drinking water
>> in the urban area (the province up country). By using UV from sunlight
>> to disinfect the normal flora in water by bring the bottle of water to
>> in sunlight for more than 12 hrs. This is the easy way to produce when
>> there are no sterile expensive equipments. It can kill the pathogens in
water as well.

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