Harnessing microbially mediated redox processes for sustainable water treatment

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With the international community under considerable pressure to reduce greenhouse gas emissions as part of climate change mitigation strategies, the development of low carbon footprint, sustainable technologies is critical to humanity's adaptation to our changing climate. Given the UN's Sustainable Development Goal 6 (SDG6), which aims to achieve universal access to safe and affordable drinking water for all by 2030, the need for low cost and sustainable global wastewater treatment systems, has rapidly become more urgent. This project will use an interdisciplinary approach, exploiting the natural interaction of iron-rich sedimentary minerals with indigenous microbial communities, to treat wastewater via a novel advanced oxidation process (AOP) and remove target organic pollutants, at very low cost. Although these coupled biogeochemical processes can occur in isolation in the laboratory, it is not yet clear whether this potentially dynamic system is able to self-regenerate and therefore perform effective treatment of water pollutants over several oxidation-reduction (redox) cycles and under realistic environmental conditions. This project aims to address these knowledge gaps, by: a) monitoring the treatment performance over several cycles of treatment and regeneration at mesocosm scale, using only water flow and column saturation for stimulating reducing environments and oxidation; b) investigating the naturally present microbial communities that drive iron reduction during regeneration periods, their evolution over several treatment cycles, and how this affects treatment efficiency; c) examining whether and how network ecology tools and geochemical parameters can be used to evaluate the performance of this sustainable wastewater treatment system. To provide the proof of concept for this wastewater treatment system, laboratory mesocosm experiments will be undertaken using different combinations of iron-rich clay minerals and redox-active sediments (including in-situ indigenous microbiology) to treat selected organic pollutants. Water flow and oxygen saturation will be adjusted over time to stimulate successive redox cycles that would occur in the natural environment. Collection of time-series data sets on contaminant degradation, changes in mineralogy and microbial communities will allow for assessing how the in-situ microbiology of the system affects the performance of, and is affected by, the treatment process. Applying a combination of geochemical, engineering, microbiological and ecological methods to understand the interactions and underpinning processes in the mesocosm experiments will be crucial for further developing this novel water treatment technology at scale.