Effect of influent COD/SO42- ratios on UASB treatment of a synthetic sulfate-containing wastewater

摘要

The effect of the chemical oxygen demand/sulfate (COD/SO42-) ratio on the anaerobic treatment of synthetic chemical wastewater containing acetate, ethanol, and sulfate, was investigated using a UASB reactor. The experimental results show that at a COD/SO42- ratio of 20 and a COD loading rate of 25.2 gCOD L-1 d(-1), a COD removal of as high as 87.8% was maintained. At a COD/SO42- ratio of 0.5 (sulfate concentration 6000 mg L-1), however, the COD removal was 79.2% and the methane yield was 0.20 LCH4 ! gCOD(-1). The conversion of influent COD to methane dropped from 80.5% to 54.4% as the COD/SO42- ratio decreased from 20 to 0.5. At all the COD/SO42- ratios applied, over 79.4% of the total electron flow was utilized by methane-producing archaea (MPA), indicating that methane fermentation was the predominant reaction. The majority of the methane was produced by acetoclastic MPA at high COD/SO42- ratios and both acetoclastic and hydrogenthrophic MPA at low COD/SO42- ratios. Only at low COD/SO42- ratios were SRB species such as Desulfovibrio found to play a key role in ethanol degradation, whereas all the SRB species were found to be incomplete oxidizers at both high and low COD/SO42- ratios. (C) 2015 Elsevier Ltd. All rights reserved.