Tim Castillo is a Wastewater Facility Manager at Rivanna Wastewater Treatment Plant in Charlottesville, Virginia. He gave us a tour of the Rivanna facility, gave a presentation on the wastewater treatment process, and sent us data from the Rivanna plant with regular to influent and effluent concentrations of various compounds. We have corresponded with Mr. Castillo throughout the project.

Before our visit to Rivanna, the team had already decided we would be concentrating our efforts in wastewater treatment. We had conducted research into where wastewater originates and what kind of consequences exist, both pathogenic and environmental, if it goes untreated. The purpose of our visit, then, was to gain insight into what a device to improve the efficiency of wastewater treatment processes would look like.

While Castillo gave us a full tour, we were focused specifically on the Bardonpho process. This five-step process is the Biological, or Secondary, treatment because it uses bacteria to remove harmful compounds. We were focused on ammonia, as our previous research indicated the importance of keep effluent ammonia levels low. The Bardonpho process is multiple steps because, within the process, oxygen concentrations vary between anaerobic, anoxic, and aerobic. In the aerobic condition, aerators pump air to fuel nitrification. Nitrification is the oxidation of ammonia to nitrites, which are then converted to nitrates.

Professor Mills of the Environmental Sciences Department at UVA has worked extensively with wastewater and the bacteria involved in its processing. We approached him as we were finalizing the design of our project.

Mills provided Insight into the best way to culture Paracoccus denitrificans and Nitrosomonas europaea, but more importantly, our discussion helped us find a niche for our project. From our meeting with Tim Castillo, we knew that aeration costs accounted for a major portion of wastewater treatment energy bills. The goal of our device, we hope, is to slash these costs by oxidizing ammonia at a lower oxygen demand. Professor Mills revealed that this is already a process for oxidizing ammonia anaerobically, called Anammox (ANaerobic AMMonium OXidation). He was optimistic that this microbial process would one day revolutionize wastewater treatment. The problem with Anammox today is its highly restrictive growth rate and extreme sensitivity to oxygen. Aside from the infrastructural changes that would need to take place for Anammox’s implementation, there is clearly further research to be done before it can be maximally harnessed in treatment plants. While we look forward to the use of Anammox in the future, we found a niche for our device. It can flourish in the transition, functioning more efficiently than current methods without requiring the major infrastructure changes of Anammox. Our time with Professor Mills helped provide context and scope for the project.

Professor Mills also provided additional considerations that went into our experimental design. He helped teach us how to culture bacteria anaerobically. Once our device is fully functioning in wastewater aerobically, we want to find the level of aeration necessary for efficient, yet cost-effective functioning. To do so, we will culture our device anaerobically first, and in ensuing experiments, test at varying oxygen concentrations.

Our kinetic model makes it possible to predict and monitor the concentrations of denitrification intermediates, many of which are harmful to the environment. For instance, according to Pan et al. (2014), nitrous oxide N₂O is "[...] a potent greenhouse gas with a 300-fold stronger radiative force than carbon dioxide, and is also [the] primary ozone depleting substancein the 21st century". If accumulation of any intermediate is a concern, our model allows one to simulate a range of conditions and pick the one where no such issues occur. See our modeling page for details!