Non-sealed water hastens the efficiency of microbial electrochemical remediation system

Abstract

Soil petroleum hydrocarbon contamination has become a global problem and microbial remediation is a friendly technology. The scarcity of electron acceptors and the low activity of functional microbes are limiting factors which are overcome by the soil microbial electrochemical system (MES). Using the petroleum hydrocarbon polluted soils as substrates, soil MESs were constructed with four different water-sealed levels to optimize the system configuration. After 65 days of operation, the accumulated charge of the group with the lowest water level (MES0) was 1282 C, while that of the highest water level group (MES5) was only 151 C. Compared with the original soil (OS), the hydrocarbon removal near the anode and cathode in MES0 were 28%–30%, which were 4%–11% higher than those in MES5. Additionally, the co-occurrence networks analysis revealed dominance in positive than negative links among bacterial, fungal, and archaeal communities in MES0 compared to MES5 and OS. In MES0 bacteria were more densely populated and connected into more closely related groups with higher interactions than those in MES5 as well as in OS. Contrary to bacteria, MES5 favored the growth and connections of fungal and archaeal communities compared to those in MES0. The above changes were ascribed to the dissolved oxygen, redox potential, and reduction of resistance, which shifted the electron acceptors hence contributing to the process of electrons and substrates transfer in soil, suggesting that bacteria synergistically cooperated with fungi, and archaea in the removal mechanisms of hydrocarbons in the MES. Our findings revealed the optimization of low water seal on the MES performance by providing a detailed overview of the synergistic behavioral characteristics of bacterial, fungal, and archaeal in soil MESs.