Unraveling nitrogen removal and microbial response of marine anammox bacteria-dominated consortia to Mo(VI) addition in nitrogen-laden saline wastewater treatment

Enhanced performance of anammox process has attracted public attention in treating saline wastewater with marine anammox bacteria. The addition of some key metal elements would enhance metabolic activity in wastewater treatment. Herein, responses of marine anammox bacteria (MAB) to Mo(VI) addition were explored in nitrogen-laden saline wastewater treatment. The experiment was conducted at a low temperature (15 ± 1 °C). With the optimal Mo(VI) concentration of 2.1 mg/(g VSS), the substrate removal rate reached the maximum of 1.41 kg N/(m³·d). Specific anammox activity and substrate conversion rate increased by 16.0% and 36.9%, respectively. The lower ΔNO₂^--N/ΔNH₄⁺-N indicated the presence of the potential electron acceptor. Moreover, the relative abundance of Cadidatus Scalindua increased by 4.18% during this experiment. Dynamic analysis showed that the remodified Logistic model was proper to analyze nitrogen removal with Mo(VI) addition. An appropriate Mo(VI) dosage (0.5–4 mg/L) would shorten the lag time of anammox process greatly.