Effects of sulfate on microbial community structures and organic fatty acid utilization in acclimated anaerobic sludges

Abstract

Sulfate is the last oxidized form of sulfur which is readily soluble in water, so it occurs naturally in most water supplies and is present in wastewater as well. Under anaerobic condition, sulfate has been known to be reduced into sulfide by sulfate reducing bacteria(SRB) using organic substrates such as volatile fatty acid(VFA) and hydrogen and give large influences on the anaerobic methanogenesis and activities of other microorganisms. Many studies have been done about the role of sulfate and SRB during the anaerobic methanogenesis in various in situ ecosystems but haven``t provide common characteristics which can be accurately applied into evaluating anaerobic degradation. In this studies anaerobic sludge which has the same origin was acclimated in laboratory scale(12L) differently under the condition of sulfate-added(S) and non-sulfate-added(N) in the influent media. The investigation relevant to characteristics of VFAs utilization, and effects of nitrogen compounds, 16S rDNA sequence of these sludges was carried out. We intended to show the effects of sulfate on the anaerobic methanogenesis through comparing those above results. In utilization of VFAs, there was large difference in metabolism. Acetate was a main intermediate of anaerobic organic metabolism under the presence of sulfate. Propionate was also produced but the amount was equivalent to 25% of acetate while conventional fermentation was mainly occurred when sulfate is absent. Propionate known to be main product of fermentation was produced as major intermediate during the non-sulfate methanogenesis. As sulfate reducing activity was disappeared the role of propionate-producing bacteria became to be enlarged. it is possible to elucidate that SRB and sulfate plays a major role in propionate or other substance degradation. However sulfidogenic activity with propionate was very low(16%) than with any other VFAs(43%). The activity was most high on acetate and butyrate. So SRB was thought to play maj...