Inactivation of Pseudomonas aeruginosa in electrochemical advanced oxidation process with diamond electrodes.

The electrochemical advanced oxidation process (EAOP) with diamond electrodes may serve as an additional technology to the currently approved methods for water disinfection. Only few data exist on the microbicidal effect of the EAOP. The aim of our study was to investigate the microbicidal effect of a flow-through oxidation cell with diamond electrodes, using Pseudomonas aeruginosa as the test organism. Without electrical current the EAOP had no measurable effect on investigated microbiological and chemical parameters. For direct electrical current a stronger impact was observed at low flow rate than at higher flow rate. Depending on the contact time of the oxidants and the type of quenching reagent added, inactivation of P. aeruginosa was in the range log 1.6-3.6 at the higher flow rate and log 2.4-4.4 at the lower rate. Direct electrical current showed a stronger microbicidal effect than alternating current (maximum reduction log 4.0 and log 2.9, respectively). The microbiological results of experiments with this EAOP prototype revealed higher standard deviations than expected, based on our experience with standard water disinfection methods. Safe use of an EAOP system requires operating parameters to be defined and used accurately, and thus specific monitoring tests must be developed.

Escherichia coli and enterococci are sensitive and reliable indicators for human, livestock and wildlife faecal pollution in alpine mountainous water resources.

AIMS: This study evaluated the applicability of standard faecal indicator bacteria (SFIB) for alpine mountainous water resources monitoring. METHODS AND RESULTS: Escherichia coli, enterococci (ENTC) and Clostridium perfringens were investigated by standard or frequently applied phenotypic and genotypic methods in a broad range of animal and human faecal sources in a large alpine mountainous area. Clostridium perfringens occurred only in human, livestock and carnivorous source groups in relevant average concentrations (log 4·7-7·0CFU g(-1) ) but not in herbivorous wildlife sources. Escherichia coli proved to be distributed in all faecal source groups with remarkably balanced average concentrations (log 7·0-8·4CFU g(-1) ). Except for single faecal samples from the cattle source group, prevalence rates for ENTC source groups were generally >87% with average concentrations of log 5·3-7·7 CFUg(-1) . To test the faecal indication capacity in the environment, faecal prevalence data were comparatively analysed with results from the concurrently performed multi-parametric microbial source tracking effort on karst spring water quality from the investigated alpine mountainous catchment (Reischer et al. 2008; Environ Microbiol 10:2598-2608). CONCLUSION: Escherichia coli and enterococci are reliable faecal indicators for alpine mountainous water resources monitoring, although E. coli is the more sensitive one. Clostridium perfringens did not prove to be an indicator of general faecal pollution but is suggested a conservative microbial source tracking marker for anthropogenic faecal influence. SIGNIFICANCE AND IMPACT OF THE STUDY: Applicability of SFIB is currently hotly debated. This is the first study providing comprehensive information on the applicability of SFIB at alpine mountainous habitats.

Acid phosphatase test proves superior to standard phenotypic identification procedure for Clostridium perfringens strains isolated from water.

Clostridium perfringens is used as an indicator for persistent faecal pollution as well as to monitor the efficacy of water treatment processes. For these purposes, differentiation between C. perfringens and other Clostridia is essential and is routinely carried out by phenotypic standard tests as proposed in the ISO/CD 6461-2:2002 (ISO_LGMN: lactose fermentation, gelatine liquidation, motility and nitrate reduction). Because the ISO_LGMN procedure is time consuming and labour intensive, the acid phosphatase test was investigated as a possible and much more rapid alternative method for confirmation. The aim of our study was to evaluate and compare confirmation results obtained by these two phenotypic methods using genotypically identified strains, what to our knowledge has not been accomplished before. For this purpose, a species specific PCR method was selected based on the results received for type strains and genotypically characterised environmental strains. For the comparative investigation type strains as well as presumptive C. perfringens isolates from water and faeces samples were used. The acid phosphatase test revealed higher percentage (92%) of correctly identified environmental strains (n=127) than the ISO_LGMN procedure (83%) and proved to be a sensitive and reliable confirmation method.