Research on the redox behavior changes of humic-like substances wastewater during electrochemical oxidation process and using the treated effluent to improve the heavily contaminated soil: Taking petroleum hydrocarbon contaminated soil as example

Humic-like substance-containing wastewater is the main type of wastewater. This study investigated the redox behavior of organic matter during the treatment process of humic-like substances by electrochemical oxidation as well as the feasibility of improving heavily polluted soil (using petroleum hydrocarbon contaminated soil as an example) with the effluent from different treatment levels. Molecular spectrum analysis and electrochemical analysis showed that the quinone and aromatic groups of the humic-like substances were degraded by electrochemical oxidation, directly leading to a decreased electron donating capability. Meanwhile, this process promoted the formation of protein-like substances and fulvic-like substances, and was accompanied by an improved electron accepting capability. Since the increasing amount of electron accepting capability was greater than the decreasing amount of electron donating capability throughout the whole process, the electrochemical oxidation process increased the total electron transfer capacity of the organic matter. In addition, bioinformatic analysis shows that the organic matter in the treated effluent enhanced the activity and abundance of dominant indigenous microorganisms in petroleum hydrocarbon contaminated soil, which is advantageous to the natural remediation of heavily polluted soils based on degradation by indigenous bacteria. This study provides a detailed basis for understanding the electrochemical degradation process of humic-like substances as well as the resource utilization of residual organic matter after electrochemical treatment of humic-like substance-containing wastewater. (C) 2020 Elsevier Ltd. All rights reserved.