An integrated process of electrochemical membrane reactor coupled with O3 and aerobic biological treatment for organic removal from soil leachate during contaminated soil remediation

The development of integrated treatment processes is essential for the effective removal of organic pollutants from soil leachate generated during the remediation of contaminated sites. The goal of this study is to develop an integrated process combining an electrochemical membrane reactor (ECMR) with O 3 and subsequent aerobic biological treatment for the treatment of leachate derived from persulfate-based advanced oxidation process (PS-AOP) remediation, where acetonitrile (ACN) was employed as a co-solvent. The results showed that the ECMR-O 3 system achieved 62.5 % chemical oxygen demand (COD) removal from leachate within 120 min (initial COD: 1116 ± 30 mg L –1 , conductivity: 21.36 ± 2.1 mS cm −1 ), under optimized conditions (operating voltage 2.5 V, permeate flux: 120 L m –2 h −1 , O 3 flow rate: 200 mL min −1 ). This performance significantly exceeded that of the individual ECMR (8.4 %) ‌or O 3 system (26.6 %). The ECMR-O 3 effluent was then subjected to aerobic biological treatment, which further reduced COD and total nitrogen (TN) to 28.3 mg L –1 (97.5 % removal) and 58.3 mg L –1 (70.5 % removal), respectively. Simultaneously, the effluent NO 3 - -N concentration decreased to 47.9 mg L –1 . 16S rRNA high-throughput sequencing revealed a targeted enrichment of dominant bacterial genera (e.g., Hydrogenophaga sp., 22.62 %; Thauera sp., 29.87 %), indicating microbial community reorganization as an ecological optimization mechanism that enhanced nitrogen removal. Furthermore, a potential degradation pathway for ACN was proposed. In summary, this integrated approach provides an efficient and viable strategy for treating refractory organic pollutants in soil leachate derived from PS-AOP remediation.