Drinking Water Biofiltration: Addressing 21st Century Challenges

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Biofiltration has become an important process in drinking water treatment. The process uses a granular media filter (usually sand, anthracite or granular activated carbon) in which a biofilm is encouraged to develop. Biofiltration can remove biodegradable substances, including specific contaminants, as well as remove particles. The long-term goal of this research program is to increase the fundamental understanding of biological filtration (biofiltration) in drinking water treatment. Facilitating its use contributes to greener and more sustainable treatment processes. Understanding and improving biofiltration has been a major focus of the applicant's research for a number of years, including his most recent Discovery Grant. Drinking water treatment, including biofiltration, faces new challenges. The proposed research will focus on three of them for the next five years: cyanotoxins, microplastics/nanoplastics, and pretreatment for reverse osmosis desalination. The following specific objectives will be addressed in this granting period: Objective 1: To further develop our understanding of the role of the biofilm community in a biofilter's ability to remove cyanotoxins (specifically microcystin-LR) during an algal/cyanotoxin bloom) Objective 2: To understand the ability of biofiltration to remove micro- and nanoplastics Objective 3: To understand and improve the ability of biofiltration to provide greener pretreatment for reverse osmosis membranes used in desalination The cyanotoxin microcystin-LR is a regulated parameter in Canada. Cyanotoxins can be removed by biofiltration, however this is not immediate during a bloom, because acclimation is required. It is important to develop a mechanistic understanding of the factors that impact a biofilter's response to a cyanobacterial bloom, and the impact on the removals achieved. Drinking water is a potential route of human exposure to microplastics/nanoplastics. Although biofiltration can contribute to microplastics/nanoplastics removal, it is crucial to understand the mechanisms of removal (likely physical rather than biodegradation, because of the short contact time). The biofilm may enhance removals, compared to conventional filtration processes. This research has unique aspects because it focuses on a biofilter's physical particle removal, rather than its function as a "bioreactor". The third objective builds on previous proof-of-concept work conducted by the applicant in Singapore. That pilot scale research demonstrated the potential of biofiltration to be a greener pretreatment for reverse osmosis desalination, however much further investigation is required so that this approach might ultimately be broadly adopted. This research will provide understanding that will contribute to the provision of safe drinking water in Canada. The students conducting the research will gain valuable knowledge and experience that will help them to obtain good positions in the drinking water sector.