微生物电解系统生物阴极的硫酸盐还原特性研究

针对传统硫酸盐生物还原方法中供氢体系能耗大和氢气利用率低的特点,构建双极室微生物电解系统(microbial electrolysis system,MES),研究了微生物利用阴极作为电子供体去除废水中硫酸盐及电子利用的特性.外加电压为0.8 V时,MES生物阴极在36 h内SO2-4平均去除量为109.8 mg·L-1,平均还原速率可达73.2 mg·(L·d)-1.运行时MES的最高电流密度为50~60 A·m-3,电子回收率为(43.3±10.7)%,约90%的电子被用于还原SO2-4.微生物利用MES阴极产生的H2作为电子供体还原SO2-4,主要还原产物为溶解态的S2-和气态的H2S,还原过程主要发生在前12 h.对MES施加不同外加电压的实验显示,外加电压为0.8 V时的SO2-4去除率和电荷量都比0.4 V时高;但0.4 V情形下MES的电子回收率可达到70%,且周期结束时阴极H2低于检出限,推测微生物可以直接利用阴极的电子从而提高了能量效率.实验结果最终表明,微生物可利用MES的阴极进行代谢去除废水中的SO2-4,阳极微生物产生电子降低了系统能耗,这为含硫酸盐废水的高效低耗处理提供了新的研究思路.

Characterization of Biocatalysed Sulfate Reduction in a Cathode of Microbial Electrolysis System

In order to improve H₂ utilization efficiency and to reduce energy consumption during the hydrogenotrophic sulfate reduction process, a two-chambered microbial electrolysis system (MES) with a biocathode was constructed. The performance of MES in terms of sulfate removal and the electron utilization was studied. With an applied voltage of 0.8 V, biocathode removed about 109.8 mg·L^-1 of SO₄^2- from the wastewater within 36 h of operation, and average reductive rate reached 73.2 mg·(L·d)^-1. The highest current density obtained from the MES was 50-60 A·m^-3. The total coulomb efficiency achieved in a cycle was (43.3±10.7)%, and around 90% of the effective electrons were used by the cathode bacteria for SO₄^2- reduction. During the operation of MES, the major products of SO₄^2- bio-reduction are sulfide and hydrogen sulfide. With an applied voltage of 0.4 V, both the SO₄^2- removal rate and electron output decreased compared with that of 0.8 V; however, the electric charge efficiency obtained by the MES increased and reached 70% when 0.4 V was applied. Meanwhile, ignorable H₂ gas was detected at the end of the cycle, indicating bacteria might directly use cathode as the electron donor thus enhanced energy efficiency. The bacteria could use cathode of the MES as electron donor to reduce SO₄^2- effectively, which may provide a new method to lower energy consumption of the hydrogenotrophic sulfate reduction process, making advanced treatment for sulfate containing wastewater more affordable for practical applications.