Enhancement Of Sulfate Reduction And Simultaneous Removal Of Zinc Manganese By Biocathode In Wastewater

In view of the biological treatment of mining and other industries to discharge a large amount of sulfate wastewater containing metals,there are problems that the activity of sulfate-reducing bacteria（SRB）is limited by the lack of organic carbon sources,low p H and metal ions,resulting in a slow sulfate reduction rate,so it is of great significance for exploring an effective treatment technology for sulfate wastewater containing heavy metals In this study,by constructing bioelectrochemical systems（BESs）sulfate reduction systems,this study focuses on exploring the effects of different carbon sources and cathodic potential conditions on sulfate reduction efficiency in biological cathodes,and under the optimization of the conditions of biocathodic sulfate reduction,the synergistic removal of sulfate wastewater containing metals icons is carried out,and the main findings are as follows:Firstly,a bioelectrochemical reactor with a cathode potential of-0.5 V vs.Ag/Ag Cl was constructed to explore the effect of carbon source on the reduced sulfate performance in biocathode.The results showed that the sulfate reduction efficiency in the biological cathode was about 1.12-2.16 times higher than that of the open-circuit biological cathode.The relationship between the reduction rate of sulfate in the biological cathode and the addition of carbon source in the reactor was ethanol>sodium acetate>sodium bicarbonate,and the reduction rate of sulfate with ethanol as carbon source was 74.71±4.8%,which was relatively increased by 71.23%and 47.26%compared with the biological cathode with sodium bicarbonate and sodium acetate.High-throughput sequencing analysis showed that the addition of different carbon sources to the biological cathode caused significant differences in microbial community structure,and the main sulfate reducing bacteria in sodium bicarbonate and acetate as carbon sources were Desulfobacter and Desulfobulbus,while the main sulfate reducing bacteria with ethanol as carbon source were Desulfomicrobium and Desulfovibrio.Secondly,the effects of different cathode potentials（-0.5 V、-0.7 V、-0.9 V、-1.1 V vs.Ag/Ag Cl）on sulfate reduction were further explored,and it was found that the biological cathodic reduction effect was the best when the cathode potential was applied-0.7 V,and the sulfate reduction efficiency reached 89.93±3.7%.However,the higher cathode potential（-0.5 V）is insufficient to strengthen the sulfate reduction,and when the cathode potential（-1.1 V）is too low to inhibit sulfate reduction.High-throughput sequencing analysis showed that the relative abundance of Desulfovibrio was up to 42.4%at a cathode potential of-0.7 V,while the abundance of functional bacteria was significantly reduced at a too low cathode potential（-1.1 V）.Furthermore,under the condition optimization of biocathode reduction of sulfate,the synergistic removal of sulfate and metals in simulated metal sulfate wastewater was analyzed.The results showed that the biological cathode had efficient removal ability for single metals icons zinc and manganese,and the removal rate of Zn²⁺reached 65 mg/L to reach 86.6%,but the removal rate of Mn²⁺reached 35 mg/L was only 58.2%.The biofilm and precipitation products in the biocathode system were analyzed by Fourier infrared and XRD and XPS,and it was found that the zinc and manganese were mainly removed by the adsorption the surface of SRB,and the solid form of Zn S and Mn S with sulfate reduction products.