Autotrophic nitrogen removal for low organic wastewater treatment

Abstract

Municipal wastewater can be directly anaerobically treated to recover energy in the form of biogas. By using an autotrophic process, such as anaerobic ammonium oxidation (anammox) process, to remove the ammonium from the anaerobic effluent, one can further reduce the energy needed for wastewater treatment. Up until now, anammox has primarily been utilized to treat waste streams at elevated temperatures (>25°C) for concentrated (>500 mg N/L) flows. The challenges of anammox process are its application of the water line of municipal wastewater treatment include lower nitrogen concentrations (100 mg N/L), high organic carbon (pharmaceutical presence) and lower temperatures (20 °C). Two 20-liter moving bed biofilm reactors were used for this study, and they were run at 22 °C for 918 days after being injected with a significant amount of anamox bacteria coming from anaerobic digester suspended biomass. The specific nitrogen removal rate (NRR) and removal efficiency increased significantly, reaching values of 0.642 g N/L/d and 92% volume, respectively. Additionally, five pharmaceuticals—ciprofloxacin, norfloxacin, ofloxacin, sulfamethaxazole, and sulfadimethoxine were employed in this investigation to assess their impact on anammox activity. The diversity of anammox bacteria was impacted by the presence of the targeted pharmaceutical chemicals, but these microorganisms were able to withstand and effectively eliminate nitrogenous substances. Throughout the course of the experiment, several conditions, including anoxic and aerobic conditions, starvation and non-starvation phases, and other conditions, were observed.