Ultraviolet (UV) light reactors used for disinfection of drinking water require validation to
ensure they are delivering UV doses sufficient to protect public health. Validation methods
involve inactivation of biological surrogates (challenge organisms) or non-biological approaches
such as chemical or particle actinometry. The bacteriophage MS2 has typically been the most
frequently used challenge organism for reactor validation; it is non-pathogenic and considerably
more UV resistant than many bacterial, viral, or protozoan pathogens. However,
Cryptosporidium oocysts are significantly more sensitive and adenoviruses display much higher
levels of UV-resistance, thereby limiting the utility of MS2 as an accurate validation surrogate.
Surrogates that more closely model the response to UV of target pathogens are required. The
primary objective of this study was to evaluate the response to UV of a variety of potential
challenge organisms that might be used for reactor validation. Inactivation of MS2 was within
the 90% prediction limits specified in the US Environmental Protection Agency (USEPA) Disinfection Guidance Manual and the
response of PP7, PM2, and B. pumilus overlapped MS2 within the range of doses investigated
with 80 mJ/cm<sup>2</sup> achieving 4 - 4.5 log inactivation. The T phages were very sensitive to UV; T4,
T7 and Phi29 were the organisms that most closely modeled Cryptosporidium inactivation.
Bam35 and PRD1 were similar with a response mid-way between the T phages and the MS2
group. For many bacteriophages, their response to UV light was independent of their respective
host's response. The only organisms with UV responses falling within the adenovirus
inactivation zone were Deinococcus spp. A UV dose of 120 mJ/cm<sup>2</sup> resulted in 4.6 log, 4.0 log,
and 4.1 log inactivation of D. radiodurans, D. radiopugnans, and adenovirus 2, respectively.
Therefore, Deinococcus spp. may be good surrogates for adenoviruses in bench level testing.
Further work is necessary to determine whether they are also suitable surrogates in larger scale
reactors. Includes 32 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 590 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 14 |
| Published : | 11/01/2007 |
