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Optimization of nitrate and selenate reduction in an ethanol-fed fluidized bed reactor via redox potential feedback control

Yan, S., Cheng, K.Y., Ginige, M.P., Zheng, G., Zhou, L. and Kaksonen, A.H. (2020) Optimization of nitrate and selenate reduction in an ethanol-fed fluidized bed reactor via redox potential feedback control. Journal of Hazardous Materials . Article 123770.

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Link to Published Version: https://doi.org/10.1016/j.jhazmat.2020.123770
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Abstract

Electron donors are a major cost-factor in biological removing oxyanions, such as nitrate and selenate from wastewater. In this study, an online ethanol dosing strategy based on feedback control of oxidation-reduction potential (ORP) was designed to optimize the performance of a lab-scale fluidized bed reactor (FBR) in treating selenate and nitrate (5 mM each) containing wastewater. The FBR performance was evaluated at various ORP setpoints ranging between −520 mV and −240 mV (vs. Ag/AgCl). Results suggested that both nitrate and selenate were completely removed at ORPs between −520 mV and −360 mV, with methylseleninic acid, selenocyanate, selenosulfate and ammonia being produced at low ORP between −520 mV and −480 mV, likely due to overdosing of ethanol. At ORPs between −300 mV and −240 mV, limited ethanol dosing resulted in an apparent decline in selenate removal whereas nitrate removal remained stable. Resuming the ORP to −520 mV successfully restored complete selenate reduction. An optimal ORP of −400 mV was identified for the FBR, whereby near complete selenate and nitrate were removed with a minimal ethanol consumption. Overall, controlling ORP via feedback-dosing of the electron donor was an effective strategy to optimize FBR performance for reducing selenate and nitrate in wastewater.

Item Type: Journal Article
Murdoch Affiliation: School of Engineering and Information Technology
Publisher: Elsevier BV
Copyright: © 2020 Elsevier B.V.
URI: http://researchrepository.murdoch.edu.au/id/eprint/57405
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