Microbial sulfate reduction with acetate: process performance and composition of the bacterial communities in the reactor at different salinity levels

Microbial sulfate reduction with acetate as carbon source and electron dono r was investigated at salinity levels between 0.53 and 1.48%. The experimen t was carried out in a 2.3-l upflow anaerobic sludge blanket reactor inocul ated with granular methanogenic sludge. A pH of 8.3, a temperature of 32 +/ -1 degreesC and a chemical oxygen demand (COD)/SO42--S ratio of 2 were main tained in the reactor throughout the experiment. Sulfate reduction and the composition of the dominant bacterial communities in the reactor were monit ored. The results showed that a maximal conversion rate for SO42--S of 14 g l(-1) day(-1) and a conversion efficiency of more than 90% were obtained a t a salinity level of 1.26-1.39%. A further increase in the salinity level led to reactor instability. Denaturant gradient gel electrophoresis of 16S rDNA fragments amplified by PCR from total bacterial DNA extracted from the inoculum and reactor sludge showed that salinity level had an impact on th e composition of the bacterial communities in the reactor. However, no clea r relationship was found between reactor performance and the composition of the dominant bacterial communities in the reactor.