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Environmental problems - Chemical approaches
RESEARCH ARTICLE

Simultaneous denitrification and hexavalent chromium removal by a newly isolated Stenotrophomonas maltophilia strain W26 under aerobic conditions

Qiang An https://orcid.org/0000-0002-1717-5232 A B , Shu-man Deng A , Bin Zhao A , Zheng Li A , Jia Xu A and Jia-Li Song A
+ Author Affiliations
- Author Affiliations

A The Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Chongqing University, Chongqing 400045, China.

B Corresponding author. Email: anqiang@cqu.edu.cn

Environmental Chemistry 18(1) 20-30 https://doi.org/10.1071/EN20097
Submitted: 2 July 2020  Accepted: 4 November 2020   Published: 22 January 2021

Environmental context. Industrial development has caused the release of hexavalent chromium and nitrates into the environment. Interactions of hexavalent chromium and nitrates with microorganisms are important both for understanding environmental behaviour and for treatment options. Bacterial removal of both chromium and nitrate was optimised in waters relevant to waste streams and the environment.

Abstract. An isolated strain of the bacterium Stenotrophomonas maltophilia strain W26, is shown to be capable of the simultaneous removal of nitrate and CrVI under aerobic conditions. Notably, 10 mg L−1 of CrVI and 500 mg L−1 of nitrate were reduced by 92.6 % and 85.2 %, respectively, by strain W26. Results showed that an excellent denitrification efficiency of 96.0 % could be reached at the optimal conditions of a C/N ratio of 10, using a carbon source of trisodium citrate, at pH 7.5, and a nitrate concentration of 500 mg L−1. Strain W26 could also effectively remove high concentrations of CrVI (50 mg L−1, 93.2 %) and nitrate (700 mg L−1, 97.4 %). By using the N balance analysis, energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), the denitrification and CrVI transformation processes were verified. CrVI, immobilised on the cell surface by W26, was reduced to CrIII, through interaction with of O=C and N-H groups. This study indicates that the isolated strain W26 has the potential to treat wastewater containing combined nitrate and CrVI contamination.

Keywords: aerobic denitrification, biosorption, CrVI reduction, Stenotrophomonas maltophilia.


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