Abstract Submission: Nature-based solutions offer a low-energy choice for reclamation of wastewater that are particularly beneficial in locations with limited treatment infrastructure. It is important to understand the fate of wastewater contaminants, particularly nitrogen, in these systems. We constructed field-scale wastewater soil filtration reactors, comparing the treatment efficacy of including poplar trees (planted) to bare-soil systems (unplanted). Poplar trees (a biofuel crop) were selected to validate a potential role of resource-limited wastewater recovery facilities in the circular bioeconomy. The treatment system was tested over two years with the application of synthetic primary and secondary effluent. Planted reactors receiving tap water (control) were also maintained to document the impacts of the wastewater on the poplar trees. Greater than 70% of the applied water was recovered from the bottom of the reactors, demonstrating the potential of the reactors for direct water reclamation. Effluent was tested for N-species using Hach kits and soils were tested for the presence of N-cycling microbial genes using ddPCR. Total nitrogen and nitrate concentrations were consistently lowest in effluent from the planted reactors. The leaves from planted reactors had a higher nitrogen concentration and greater average leaf biomass than leaves from control reactors, demonstrating the active role of the trees in nitrogen removal from the wastewater. amoA gene abundance increased in the soils over the course of the experiment with exposure to ammonium and was lower in control reactors that did not receive wastewater. nirK was equally abundant across treatments, though ex-situ batch tests revealed differences in denitrification potential. These results suggested planted soils have a greater capacity for wastewater reclamation including the control of nitrogen removal.
