AWWA WQTC69478

This powerpoint presentation begins by providing a brief overview of nematodes and protection mechanisms of microorganisms in ultraviolet (UV) disinfection. Research objectives included the following: assess the significance of nematodes in terms of protecting waterborne pathogens against UV disinfection using E. coli OP50 - GFP as a surrogate for enteropathogenic bacteria, and B. subtilis spores as a possible surrogate for Cryptosporidium. Study design included the following: synchronized nematodes (adults); bacterial strains of E. coli OP50 - GFP and B. subtilis spores ATCC 6633; Chlorination - 10 ppm * 5 min for E. coli, and 15 ppm * 20 min for B. subtilis spores; Sonication: 15 W * 60 sec in 5 ml; UV exposure - collimated beam apparatus, LP, 254 nm, 2 UV fluences: 5 - 40 mJ/cm²; culture medium for bacterial counts - m-Endo for E. coli, and TSB for B. subtilis spores. Presentation conclusions indicate the following: internalization by nematode C. elegans offers significant protection to bacteria (E. coli, B. subtilis spores) against UV disinfection at typical fluence applied in WTP (40 mJ/cm²); thus, the authors suppose that pathogenic microorganisms in drinking water could survive UV disinfection treatment when protected inside nematodes; this should be taken into account when assessing the microbial risk associated to drinking water; however, the low concentration of pathogenic microorganisms in most drinking water sources suggests that pathogen ingestion by higher organisms in natural conditions remains a low probability event; and, while higher organisms are known to be ubiquitous in drinking water systems, studies are lacking in terms of quantification of internalized pathogen occurrence in field conditions. Includes 2 references, table, figures.