New technologies for wastewater resource recovery by anoxigenic photoheterotrophic biological processes

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Tightening regulations on biosolids disposal and growing energy utilization increase the operational costs of wastewater treatment plants, and reduce the sustainability of municipal infrastructures. In response, the wastewater industry is converting from only treating wastewater for environmental protection to additionally recovering resources wasted with the water. In terms of energy content, recoverable organics and nutrients (nitrogen, phosphorus) account for ~15% of the per capita electricity consumption; accordingly, recovery will improve sustainability and reduce CO2 footprint. However, recovery using current aerobic biological processes is limited. Thus, the current program will contribute to the development of new anaerobic biological processes enabling recovery. The results will improve infrastructure efficiencies and reduce burden to tax payers. Anaerobic processes pose challenges for Canada because many wastewater facilities operate below 12C for periods of up to 6 months. Indeed, anaerobic microbes typically have lower maximum growth rates than aerobic ones, resulting in lower process stability and capacity to meet discharge regulations at low temperatures. Additionally, municipal wastewater is relatively dilute for nutrient recovery, and biological concentration is necessary prior to physico-chemical extractions. We propose to use purple non-sulfur bacteria (PNSB) to address these challenges. Their ability to simultaneously obtain energy from light and carbon from organics provides them with higher biomass yields and faster growth rates than other anaerobes. Consequently, high biomass yields make them suitable for concentration of nutrients in biomass, and high growth rates reduce their sensitivity to colder operation temperatures. Finally, because they are the only photosynthetic organisms utilizing infrared light (>800 nm), engineers would possess powerful selection tools to control microbial communities in mixed open cultures. Published studies mainly focused on pure culture PNSB wastewater processes and operation at 20-35C. These conditions are inapplicable to full-scale Canadian municipal wastewater facilities; thus, significant knowledge gaps persist in developing PNSB processes. Additionally, reactor conditions need to be tightly controlled such that metabolism maximizes biomass yields instead of competing H2 and polyhydroxyalkanoate syntheses. This proposal will investigate operation conditions of non-sterile PNSB photobioreactors that are relevant to Canada for enabling implementation of wastewater resource recovery. Furthermore, control strategies for PNSB metabolism and microbial community composition will be developed by using genome-scale metabolic modeling and high-throughput metagenomic molecular tools. The program will train 2 PhD, 4 MEng and 10 undergraduate students.