Bioelectrochemical BTEX removal at different voltages: assessment of the degradation and characterization of the microbial communities

BTEX compounds (Benzene, Toluene, Ethylbenzene and Xylenes) are toxic hydrocarbons that can be found in groundwater due to accidental spills. Bioelectrochemical systems (BES) are an innovative technology to stimulate the anaerobic degradation of hydrocarbons. In this work, single chamber BESs were used to assess the degradation of a BTEX mixture at different applied voltages (0.8 V, 1.0 V, 1.2 V) between the electrodes. At the end of the experiment the microbial communities were characterized by high throughput sequencing of the 16S rRNA gene. Hydrocarbon degradation was linked to current production and to sulfate reduction, at all the tested potentials. The highest current densities applied (about 200 mA/m2 with a maximum peak at 480 mA/m2) were observed when 0.8 V were. The application of an external voltage increased the removal of toluene, m-xylene and p-xylene. The highest removal rate constants at 0.8 V, calculated for toluene, m-xylene and p-xylene, were: 0.4 ± 0.1 days-1, 0.34 ± 0.09 days-1 and 0.16 ± 0.02 days-1, respectively).At the end of the experiment, the microbial communities were characterized by high throughput sequencing of the 16S rRNA gene. Microorganisms belonging to the families Desulfobulbaceae, Desulfuromonadaceae and Geobacteraceae were enriched on the anodes suggesting that both direct electron transfer and sulfur cycling occurred. The cathodic communities were dominated by the family Desulfomicrobiaceae that may be involved in hydrogen production.

BTEX化合物（BTEX compounds），包含苯（Benzene）、甲苯（Toluene）、乙苯（Ethylbenzene）与二甲苯（Xylenes），是一类可因意外泄漏进入地下水的有毒烃类物质。生物电化学系统（Bioelectrochemical systems, BES）是一类可强化烃类厌氧降解的创新技术。本研究采用单室生物电化学系统，评估不同施加电压（0.8 V、1.0 V、1.2 V）下电极间BTEX混合污染物的降解效果。实验结束后，通过16S rRNA基因高通量测序对微生物群落进行表征。在所有测试电压条件下，烃类降解均与电流产生及硫酸盐还原过程紧密关联。施加的最高电流密度约为200 mA/m²，峰值达480 mA/m²，该现象于0.8 V施加条件下观测得到。施加外部电压可提升甲苯、间二甲苯（m-xylene）与对二甲苯（p-xylene）的去除效率。针对甲苯、间二甲苯及对二甲苯计算得到的0.8 V条件下最高去除速率常数分别为0.4 ± 0.1 d⁻¹、0.34 ± 0.09 d⁻¹与0.16 ± 0.02 d⁻¹。实验结束后，再次通过16S rRNA基因高通量测序表征微生物群落：阳极表面富集了脱硫绳状菌科（Desulfobulbaceae）、脱硫单胞菌科（Desulfuromonadaceae）与地杆菌科（Geobacteraceae）的微生物，提示直接电子转移与硫循环过程均有发生；阴极群落以脱硫微菌科（Desulfomicrobiaceae）为主，该类群可能参与氢气生成。