Microbiology and Chemistry Interactions in a Biological Sulphate-Reducing Process

摘要

In this study, we tested the industrial anaerobic sludge as inoculum for biologic sulphate removal from mine water with high sulphate (app. 10 g/L), but negligible metal concentration originating from a subarctic mine. Because of the remoteness of the mine, ethanol was chosen as substrate due to its easy storage and transportation to remote sites. Experiments were performed in three 0.7L reactors at room temperature. The reactors were operated as upflow anaerobic sludge blanket reactor (Reactor 1), and fluidized bed reactors with different carriers.Physicochemical parameters (pH, redox, sulphate, sulphide) were measured over six months and the microbiology was analysed by high throughput (HTP) sequencing. The pH in the reactors varied between 5.2 and 7 and the sulphate removal varied from -111% (indicating sulphate production) to 48% removed sulphate. In addition, up to 3.5 g L~(-1) acetate was formed at pH 7.2 - 7.4.The HTP sequencing revealed that the microbial communities changed markedly from that of the inoculum. SBR communities evolved during the experiments. The most common bacteria in the reactors belonged to sulphide- and thiosulphate- reducing Epsilonproteobacteria, the archaeal population consisted mostly of acetate-utilizing Methanosaeta - methanogens. 2 - 15% of the bacterial communities consisted of SRB. In addition, the microbial consortium contained a large variety of organic matter degrading species.A high input sulphate level and a low pH together with undissociated H_2S may inhibit growth and activity of the SRB. Elevated concentration of acetate may also inhibit the SRB. Analysis of the microbial community gives added insight into the processes. Our study also indicated that parameters normally used for following up an SBR process such as redox and pH, is not necessary sufficient for assuring a functioning process.