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Effect of elevated nitrate and sulfate concentrations on selenate removal by mesophilic anaerobic granular sludge bed reactors

Abstract

Simultaneous removal of selenate (SeO42-), nitrate (NO3-) and sulfate (SO42-), typically present in Se-contaminated wastewaters, by Eerbeek anaerobic granular sludge was investigated in batch and continuous bioreactor experiments. Batch experiments showed SeO42- removal was enhanced to 91% in simulated wastewater with SeO42-+NO3-+SO42- (1:40:100 SeO42-:NO3-:SO42- molar ratios) compared to simulated wastewater with SeO42- alone (67%). SeO42- removal was severely impacted by high concentrations of SO42- (SeO42-:SO42- > 1:300). Removal of SeO42-, NO3- and SO42- at a 1:40:100 ratio was studied in a 2 L lab-scale upflow anaerobic sludge blanket (UASB) reactor operated at 20°C, 24 h hydraulic retention time and 2 g COD L-1 day-1 organic loading rate using lactate as electron donor. The removal efficiencies were stabilized at 100, 30 and 80% for NO3-, SO42- and total Se, respectively, during 92 days of UASB operation. The total Se removal efficiencies dropped to 47% or even to a negative value when, respectively, SO42- and NO3- were sequentially excluded from the influent. Speciation of Se, particularly the microbial production of colloidal Se0 levels, was influenced by both SO42- and NO3-. The results presented here demonstrate that UASB reactors are capable of removing SeO42- in the presence of millimolar concentrations of NO3- and SO42- typically found in Se-wastewaters.

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Publication details

The article was received on 08 Aug 2017, accepted on 01 Dec 2017 and first published on 05 Dec 2017


Article type: Paper
DOI: 10.1039/C7EW00307B
Citation: Environ. Sci.: Water Res. Technol., 2017, Accepted Manuscript
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    Effect of elevated nitrate and sulfate concentrations on selenate removal by mesophilic anaerobic granular sludge bed reactors

    L. C. Tan, Y. V. Nancharaiah, E. D. van Hullebusch and P. N. L. Lens, Environ. Sci.: Water Res. Technol., 2017, Accepted Manuscript , DOI: 10.1039/C7EW00307B

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