Adapting to life in a changing climate: optimizing water treatment processes

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Many drinking water treatment plants (WTPs) now use membranes to remove harmful microorganisms. Climate change is expected to increase algal and cyanobacterial-related problems at WTPs including greater taste and odour incidents, greater fouling of membranes and the release of cyanobacterial toxins. Dissolved air floatation (DAF) is an effective process for the removal of algae and cyanobacteria, but it used in only some WTPs. Activated carbon adsorption processes are one of the best technologies for the removal of taste and odour compounds, cyanobacterial toxins and other trace contaminants; due to the 5 to 15% AC mass losses during thermal regeneration, alternative adsorbents, such as NYEX, are currently being developed. The objective of this proposal is to help improve WTPs and make them more climate-change resilient through the following initiatives. First, to develop a new bench-scale DAF testing unit, and test it for different waters, including one during an algal bloom. Second, to compare the efficiency of DAF with that of ballasted sedimentation, a competing separation process, for the treatment of water during algal blooms. The applicant's team has found that for Ottawa River water, to reduce membrane fouling pretreatment by DAF was superior to pretreatment by sedimentation. Third, to confirm if this DAF superiority is impacted by the membrane system type and the type of water treated. Planned experiments include testing during algal bloom conditions. Fourth, to continue researching the NYEX adsorption/electrochemical regeneration system as an alternative to activated carbon adsorption for the removal of trace contaminants. Specifically, the applicant's team will determine if NYEX's capacity to remove trace contaminants (such as pesticides and cyanobacterial toxins) is less impacted than that of activated carbon by the presence of natural organic matter, which is a drawback of activated carbon. All of these initiatives will help design water treatment systems that can perform better under the more frequent algal/cyanobacterial blooms expected in the future, and avoid situations like the 3-day “no drink order` in Toledo, OH in August 2014.