Abstract

The effects of ethanol/SO₄^2- ratio and pH on mesophilic sulfate reduction were investigated using three UASB reactors fed with sucrose at an organic loading rate of 5.0 gCOD/L·day. When pH was at 7, ethanol/SO₄^2- ratio rose from 0 to 5, and sulfate reduction rate went up from 5 - 7% to 85 - 89%; the removal efficiency of COD from 82 to 89%. When sucrose was the only organic carbon source, the sulfate reduction rate was 55 - 57% with pH at 6 and 47 - 49% with pH at 5. Correspondingly, the COD removal efficiencies were 46 - 49% and 8 - 10%, respectively. When ethanol was added as part of the carbon source, the sulfate reduction rates rose to 88 - 91% and 60 - 71% respectively, and COD removal efficiencies were 56 - 61% with pH at 6 and 27 - 29% with pH at 5. Decrease of pH resulted in significant decline of specific methanogenic activity and high accumulation of volatile fatty acid. Addition of ethanol promoted sulfate reduction rate and facilitated good synergetic metabolism of sulfate-reducing and methane-producing bacteria. The results presented in this paper provide some useful information for the optimization of sulfate-reducing processes in wastewater treatment.

Key words: UASB, SRB, MPB, sulfate reduction, ethanol, methanogenic activity.