EFFECTS OF NaCL ON MESOPHILIC SULFATE REDUCTION AND COD REMOVAL IN AN ANAEROBIC DIGESTION PROCESS

摘要

In order to investigate the effects of NaCl on meso-philic sulfate reduction and COD removal in anaerobic digestion processes, an up-flow anaerobic sludge bed (UASB) was operated continuously for 190 d with a constant hydraulic retention time (24h) at different COD/SO_4~(2-) ratios. With an increase in NaCl concentration from 0 to 4 g L~(-1), the sulfate reduction and COD removal were elevated significantly, but the higher salinity had a negative impact on the bioreactor performance. The maximum sulfate reduction efficiencies were obtained to be 84.66%-90.01% at COD/SO_4~(2-) ratios of 10 and 5, respectively. With NaCl concentration enhancing, COD removal was increased from 50.23% to 75.19%, followed by a dramatic drop. At a NaCl concentration of 50 g L~(-1) in the bioreactor, more than 60% sulfate reduction and less than 30% COD removal were achieved. Quantitative real time PCR showed that the highest abundance of SRB was obtained at a NaCl concentration of 4 g L~(-1), which was consistent with the results of sulfate reduction and COD removal. The result obtained suggesting that sulfate reducing bacteria (SRB) was unsusceptible to high salt than methane-producing bacteria (MPB) and could be potentially applied in the hypersaline environments.