UV light effect on fecal coliforms, fecal streptococci, Salmonella typhi and Acanthamoeba spp.

Abstract

The aim of this work was to evaluate the efficiency of UV-light to inactivate indicators of fecal contamination, Salmonella typhi and Acanthamoeba spp., in three different secondary effluents from biological treatment. Even though effluents differed in terms of their suspended solids content, transmittance, and particle size distribution, the UV-light dose required to meet WHO agricultural water reuse criteria was 30 mW·s/cm2, this was so because the particle content with sizes >40 ¼m was similar and very low for the three effluents. Using this dose, 3 log of Salmonella typhi and fecal streptococci were also inactivated. However, to avoid fecal coliform and Salmonella typhi photoreactivation and to inactivate 2.5 log of Acanthamoeba spp., the UV dose had to be doubled. Results regarding Acanthamoeba spp. UV inactivation are interesting because their pathogenicity, presence in wastewater, and resistance to conventional disinfection processes have been reported in literature. It was found that the fecal coliforms' inactivation coefficient was the lowest of all the bacteria studied (Salmonella typhi and fecal streptococci), suggesting the limitation of this indicator when several kinds of pathogens are present, as is the case in developing countries.