Development of sulfate reducing bacteria based anaerobic wastewater treatment system combined with sulfide fuel cell

Abstract

As an alternative for energy intensive aerobic wastewater treatment system, development of sulfate reducing bacteria (SRB)-based anaerobic domestic wastewater treatment system was studied. This proposed energy conservative wastewater treatment system has main advantageous factors of no requirement of aeration, fast substrate utilization and less sensitiveness of SRB. Sulfate for SRB’s synthesis could be supplied from SOx in industrial gas, thus the system also can contribute to the economical treatment of hazardous sulfur compound in the gas. With the dissolved sulfate as an electron acceptor, SRB degrade organic matters in wastewater and produce sulfide in continuously operating upflow anaerobic sludge blanket reactor (UASBr). Also the produced sulfide is used as an electron donor for electricity generation in sulfide fuel cell system connected to the UASB reactor. This study focuses on obtaining SRB dominant granule from methanogen dominant anaerobic granule in a competition between SRB and methanogens. As a strategy to increase SRB activity and to suppress methanogens, starvation was applied by not providing organic source but continuous supplying sulfate. Based on the well adopted hypothesis on the granule structure, methanogens located relatively inner core of a granule died out due to the lack of organic source, while SRB located at outer part of granule survived utilizing extracellular polymeric substance (EPS) or organic matters from died out microbes as an organic source. By eliminating the competition, the portion of organic matter degradation by SRB was increased from 19% before starvation to 93% after starvation, achieving 80% COD removal in total. In case of sulfate removal, 20% improvement was achieved compared to the control reactor. This effect of starvation on the granule characteristics were confirmed with scanning electron microscope (SEM) and transmission electron microscope (TEM). In addition, increased population of SRB and decreased meth...