ENG-BIOTECH: Enhancing conditions for comammox bacteria to facilitate mainstream anammox processes.

Conventional nitrogen removal in wastewater treatment systems is highly energy intensive, accounting for nearly 30% of the total energy demand in the plant. In addition, conventional nitrogen removal processes emit nitrous oxide to the atmosphere, which is a highly potent greenhouse gas. Thus, the energy demand and greenhouse gas emissions of nitrogen removal processes have a large impact on the carbon footprint of wastewater treatment. This project will advance novel biological treatment strategies that use highly specialized comammox and anammox bacteria for nitrogen removal as opposed to conventional nitrifying bacteria. This process holds great promise to reduce the carbon footprint of wastewater treatment by lowering energy demand and reducing greenhouse gas emissions. This research project also includes substantial collaboration with wastewater utilities ensuring that the outcomes will rapidly translate to industry benefits. This collaboration also provides a unique opportunity for training of undergraduate and graduate students by academic researchers and industry practitioners. The goal of this project is to advance the sustainability of wastewater treatment by systematically investigating the recently discovered synergistic nitrogen removal by comammox and anammox bacteria in a full-scale mainstream nitrogen removal process. Specific research objectives designed to achieve this goal include: i) evaluating the impact of nitrogen loading rates on the synergy between comammox and anammox bacteria, ii) determining the impact of dissolved oxygen concentrations on mechanisms governing nitrite provision to anammox bacteria, and iii) conducting pilot-scale testing of two different process configurations that leverage comammox and anammox bacterial synergy for nitrogen removal. Using anammox bacteria in mainstream nitrogen removal has the potential to reduce aeration costs by nearly 60%, thus significantly reducing the carbon footprint of the wastewater treatment sector. Further, shifting aerobic nitrification from strict ammonia-oxidizing bacteria to comammox bacteria combined with potentially eliminating the need for denitrification will substantially reduce nitrous oxide emissions from wastewater treatment. A better understanding of comammox-anammox synergy will also have a beneficial impact on nitrogen pollution management in other sectors like agriculture where managing the nitrogen cycle is becoming increasingly urgent. This industry-facing interdisciplinary project will also provide a unique opportunity for graduate and undergraduate researchers to be mentored by academics and industry practitioners. These training and stakeholder engagement efforts will contribute to a skilled and diverse STEM workforce. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.