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BACKGROUND Bacteria capable of heterotrophic nitrification–aerobic denitrification have received increasing attention, and can achieve simultaneous nitrification and denitrification processes to accelerate nitrogen removal rate. However, heavy metals in industrial wastewater seriously affect the nitrogen removal by these bacteria. Thus, this work focused on the nitrogen removal ability of a metal‐resistant bacterium Pseudomonas putida ZN1. RESULTS ZN1 effectively removed ammonium, nitrate and nitrite with maximum removal efficiencies of 97.47%, 86.08% and 71.57%, and it also preferred to utilize ammonium during the simultaneous nitrification and denitrification process. The inhibitory effect of heavy metals on ammonium removal decreased in the order Ni2+ > Cr6+ > Zn2+ > Cu2+, and copB‐I was responsible for the higher copper tolerance of ZN1. The nitrogen removal pathway of ZN1 was proposed to be heterotrophic nitrification combined with aerobic denitrification through the nitrogen source utilization, gas detection, enzyme assay and gene amplification. CONCLUSION ZN1 exhibited excellent heterotrophic nitrification and aerobic denitrification capacity, and it effectively removed ammonium from wastewater containing the heavy metals Cu2+, Zn2+, Cr6+ and Ni2+. All results make strain ZN1 a promising candidate for future application in treating actual wastewater. © 2018 Society of Chemical Industry

In this study, the γ-MnO 2 catalyst modified with PEG exhibits outstanding low-temperature performances for NO oxidation, and in-situ DRIFTS experiments were used to systematically investigate the low-temperature NO oxidation mechanisms over γ-MnO 2 . These results demonstrated that NO was first adsorbed on the surface of γ-MnO 2 to form the nitrosyls, which could be further oxidized to nitrates under the action of the chemisorbed oxygen or lattice oxygen, and afterwards the formed nitrates were decomposed into nitrogen dioxide. Moreover, the inhibitory mechanism of SO 2 on γ-MnO 2 was also studied, and SO 2 severely inhibit the NO oxidation performance of γ-MnO 2 through forming stable sulfates that could easily consume the active sites of the catalyst to hinder the formation of nitrates, resulting in the termination of oxidation of NO to NO 2 . Clarifying the mechanisms of NO oxidation and SO 2 poison is very essential for developing better NO oxidation catalysts.