Issue 2, 2018

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 that 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, a 24 h hydraulic retention time and a 2 g COD L−1 day−1 organic loading rate using lactate as the 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-contaminated wastewaters.

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

Supplementary files

Article information

Article type
Paper
Submitted
08 Ago 2017
Accepted
01 Des 2017
First published
05 Des 2017

Environ. Sci.: Water Res. Technol., 2018,4, 303-314

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., 2018, 4, 303 DOI: 10.1039/C7EW00307B

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