Assessment of indigenous surrogate microorganisms for UV disinfection dose verification

Abstract

UV disinfection reactors are an effective and economic means to inactivate oocysts of the protozoan parasite Cryptosporidium in drinking water. Cryptosporidiosis outbreaks can occur as a result of filter breakthrough following increased oocyst loading of treatment processes (Bouchier, 1998). Oocysts are resistant to commonly used chlorine-based disinfectants and therefore filter failure can result in outbreaks of cryptosporidiosis (Korich et al., 1990). Low and medium pressure UV disinfection has been demonstrated to be effective at reducing oocyst infectivity at economic UV doses, and hence UV reactors have become increasingly common as drinking water treatments for inactivating oocysts and other waterborne pathogens

Immunological detection of thymine dimers in indigenous genomic DNA from pre-disinfection drinking water as an ultraviolet disinfection dosimeter

“…average. 16 It is noted that high UV doses gave the lowest DNA recovery in both cases at plant 1, but this was not the case at Plant 2. UV dose did not seem to affect DNA recovery in a predictable fashion.…”

“…However, the total number of individual heterotrophic bacterial species are unlikely to be sufficient to use in routine dose verification and the culturable population in drinking water is likely a minority in the context of the total microbial population. [14][15][16] This suggests culture-based methods, while the basis of validation, are of limited use for routine verification. [14][15][16] The biological mechanism of UV disinfection is based on the absorbance of UV light by nucleic acids, although a contribution for UV absorbance by proteins is increasingly becoming apparent.…”

“…[14][15][16] This suggests culture-based methods, while the basis of validation, are of limited use for routine verification. [14][15][16] The biological mechanism of UV disinfection is based on the absorbance of UV light by nucleic acids, although a contribution for UV absorbance by proteins is increasingly becoming apparent. 17,18 DNA, RNA and proteins absorb UV light over a broad range of wavelengths, but UV-C light (220-300 nm) is often referred to as the germicidal range.…”