Utilization of Distillery Wastewater in a Microbial Fuel Cell Based on Microbial Sulfate Reduction

Simple electron donors (such as lactate, ethanol, glucose, etc.) in the process of microbial sulfate reduction are well studied. In search of new substrates for sulfate-reducing bacteria, multicomponent organic products were investigated. The application of distillery wastewater (vinasse and ethanol stillage) as electron donors in a microbial sulfate reduction process with an integrated microbial fuel cell was studied. The results were compared with those of lactate as a control. The influence of the rate of volumetric sulfate loading on the rate of microbial processes was studied using six different hydraulic retention times: 14, 18, 22, 26, 30 and 34 hours. During the process, sulfate-reducing bacteria incompletely oxidize organic matter in the used distillery wastewater and generate large amounts of acetic acid, and propionic acids as a product of other microbiological processes. The rates of sulfate and organic removal for all three substrates increase with increasing retention time. In the case of vinasse and stillage at the 34th hour, sulfate removal was 98%, and organics removal was 48 and 44%, respectively. The open circuit voltage values for both fuel cells with wastewaters were highest at the 22nd hour. The results showed that vinasse and ethanol stillage were suitable electron donors in the process of microbial sulfate reduction and the resulting metabolites can be a substrate for other anaerobic processes.