Innovative method for prioritizing emerging disinfection by-products (DBPs) in drinking water on the basis of their potential impact on public health.

Providing microbiologically safe drinking water is a major public health issue. However, chemical disinfection can produce unintended health hazards involving disinfection by-products (DBPs). In an attempt to clarify the potential public health concerns associated with emerging disinfection by-products (EDBPs), this study was intended to help to identify those suspected of posing potential related health effects. In view of the ever-growing list of EDBPs in drinking water and the lack of consensus about them, we have developed an innovative prioritization method that would allow us to address this issue. We first set up an exhaustive database including all the current published data relating to EDBPs in drinking water (toxicity, occurrence, epidemiology and international or local guidelines/regulations). We then developed a ranking method intended to prioritize the EDBPs. This method, which was based on a calculation matrix with different coefficients, was applied to the data regarding their potential contribution to the health risk assessment process. This procedure allowed us to identify and rank three different groups of EDBPs: Group I, consisting of the most critical EDBPs with regard to their potential health effects, has moderate occurrence but the highest toxicity. Group II has moderate to elevated occurrence and is associated with relevant toxicity, and Group III has very low occurrence and unknown or little toxicity. The EDBPs identified as posing the greatest potential risk using this method were as follows: NDMA and other nitrosamines, MX and other halofuranones, chlorate, formaldehyde and acetaldehyde, 2,4,6-trichlorophenol and pentachlorophenol, hydrazine, and two unregulated halomethanes, dichloromethane and tetrachloromethane. Our approach allowed us to define the EDBPs that it is most important to monitor in order to assess population exposure and related public health issues, and thus to improve drinking water treatment and distribution. It is also important to extend our knowledge about exposure to mixtures of emerging DBPs and possible related health effects.

Assessment of the removal and inactivation of influenza viruses H5N1 and H1N1 by drinking water treatment.

Since 2003, there has been significant concern about the possibility of an outbreak of avian influenza virus subtype H5N1. Moreover, in the last few months, a pandemic of a novel swine-origin influenza A virus, namely A(H1N1), has already caused hundreds of thousands of human cases of illness and thousands of deaths. As those viruses could possibly contaminate water resources through wild birds excreta or through sewage, the aim of our work was to find out whether the treatment processes in use in the drinking water industry are suitable for eradicating them. The effectiveness of physical treatments (coagulation-flocculation-settling, membrane ultrafiltration and ultraviolet) was assessed on H5N1, and that of disinfectants (monochloramine, chlorine dioxide, chlorine, and ozone) was established for both the H5N1 and H1N1 viruses. Natural water samples were spiked with human H5N1/H1N1 viruses. For the coagulation-settling experiments, raw surface water was treated in jar-test pilots with 3 different coagulating agents (aluminum sulfate, ferric chloride, aluminum polychorosulfate). Membrane performance was quantified using a hollow-fiber ultrafiltration system. Ultraviolet irradiation experiments were conducted with a collimated beam that made it possible to assess the effectiveness of various UV doses (25-60 mJ/cm2). In the case of ozone, 0.5 mg/L and 1 mg/L residual concentrations were tested with a contact time of 10 min. Finally, for chlorine, chlorine dioxide and monochloramine treatments, several residual oxidant target levels were tested (from 0.3 to 3 mg/L) with contact times of 5-120 min. The infectivity of the H5N1 and H1N1 viruses in water samples was quantified in cell culture using a microtiter endpoint titration. The impact of coagulation-settling on the H5N1 subtype was quite low and variable. In contrast, ultrafiltration achieved more than a 3-log reduction (and more than a 4-log removal in most cases), and UV treatment was readily effective on its inactivation (more than a 5-log inactivation with a UV dose of 25 mJ/cm2). Of the chemical disinfection treatments, ozone, chlorine and chlorine dioxide were all very effective in inactivating H5N1 and H1N1, whereas monochloramine treatment required higher doses and longer contact times to achieve significant reductions. Our findings suggest that the water treatment strategies that are currently used for surface water treatment are entirely suitable for removing and/or inactivating influenza A viruses. Appropriate preventive actions can be defined for single disinfection treatment plants.