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The increasing lack of drinking water around the globe is of great concern. Although UV irradiation, photocatalysis, and electrocatalysis for bacterial disinfection have been widely explored, the synergistic kinetics involved in these strategies have not been reported to date. Herein, we report on an efficient and cost-effective strategy for the remediation of a model bacterium (E. coli), through the integration of photochemistry and electrochemistry based on a bifunctional electrode, which utilizes titanium (Ti) as the substrate, nanoporous titanium dioxide (TiO 2 ) as a photocatalyst, and ruthenium oxide (RuO 2 ) nanoparticles as an electrocatalyst. The nanoporous TiO 2 was grown directly onto a Ti substrate via a three-step anodization process, and its photocatalytic activity was significantly enhanced by a facile electrochemical treatment. A high disinfection rate at 0.62 min -1 , with >99.999% bacterial removal within 20 min was achieved using the novel TiO 2 /Ti/RuO 2 bifunctional electrode. Complete bacterial disinfection was attained within 30 min as assessed by a spread plate method. Bacterial survival strategies, including a viable but non-culturable state of the bacteria, were also investigated during the bifunctional treatment process. The novel strategy demonstrated in this study has strong potential to be utilized for water purification and wastewater treatment as an advanced environmentally compatible technology., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A total of 177 naturally contaminated water samples were analyzed by membrane filtration according to the Standard Methods for the Examination of Water and Wastewater published by the American Public Health Association. Filters were incubated in parallel on mHPC-agar and 3M Petrifilm Aerobic Count Plates (Petrifilm AC plates) for heterotrophic counts. Fecal coliforms and Escherichia coli were enumerated on mFC-agar and 3M Petrifilm E. coli/Coliform Count Plates (Petrifilm EC plates). Typical colonies on each media type were confirmed following standard procedures. Heterotrophic counts were between 10(3) and 10(4) CFU/mL and the average log10 counts obtained on Petrifilm AC plates were about two-fold lower than on mHPC-agar. Counts for fecal coliforms and E. coli were between 10(2) and 10(3) CFU/mL. Average log10 counts for confirmed fecal coliforms obtained on Petrifilm EC plates were slightly lower than on mFC agar with a correlation coefficient of 0.949. The average log10 counts for confirmed E. coli on Petrifilm EC plates and on mFC agar were statistically not different (P=0.126) with a correlation coefficient of 0.879. Specificity of Petrifilm EC plates and mFC agar was evaluated by comparing typical colony counts with confirmed counts. On mFC agar, counts for typical colonies were by 2 log10 CFU higher than the actual confirmed counts. In contrast, on Petrifilm EC plates typical colony counts were almost identical to confirmed colony counts for both fecal coliforms and E. coli. This comparison illustrates the high specificity of Petrifilm EC plates for enumeration of both fecal coliforms and E. coli in water.

A multiplex PCR-DNA probing assay was developed to detect four major Escherichia coli virotypes. Six highly specific polymerase chain reaction (PCR) primer sets and DIG-labeled chemiluminescent probes were designed to target the Shiga-like toxin I and II genes (stxI and stxII) of verotoxigenic E. coli (VTEC), heat-stable and heat-labile toxin genes of enterotoxigenic E. coli (ETEC), adherence factor (EAF) of enteropathogenic E. coli (EPEC) and a fragment of the invasiveness plasmid (IAL) of enteroinvasive E. coli (EIEC). The primer pairs generate products of 350, 262, 170, 322, 293 and 390 bp in length, respectively. The multiplex primers and probes were tested for specificity against 31 pathogenic E. coli strains, nine nonpathogenic E. coli and non-E.coli enteric and environmental bacterial strains. The results showed a high degree of specificity of the primers and probes for strains from corresponding virotypes and no reaction with the nontarget bacterial strains. The proposed multiplex PCR-DNA probing assay provides rapid and specific detection of four major virotypes of E. coli.