Remediation of groundwater contaminated with perfluoroalkyl acids and chlorinated ethenes using a microbial reductive dechlorination and sorptive material treatment train.

Groundwater contaminated by mixtures of perfluoroalkyl acids (PFAAs) and chlorinated ethenes (CEs) pose a significant remediation challenge due to the distinct characteristics of these two contaminant types. In situ adsorption barriers have been demonstrated as a promising remediation strategy for PFAA-contaminated groundwater plumes. However, most previous studies were carried out with only a single PFAA, and our understanding of the retention of comingled contaminant plumes, including multiple PFAAs and CEs in such barriers, remains limited. This study initially investigated the transport and retention of a mixture of 2 CEs and 10 PFAAs at concentrations relevant to contaminated sites in water-saturated sorptive columns, packed with either polyethylenimine-coated iron oxide nanoparticles (IONP) or polymer-stabilized powdered activated carbon (S-PAC). Subsequently, a treatment train, consisting of an upgradient microbial reductive chlorination column and a downgradient sorptive column, was developed and examined for the enhanced treatment of comingled PFAAs and CEs groundwater. Compared to the standalone sorptive columns, the coupled biological-sorptive treatment train achieved complete detoxification of CEs to ethene, and enhanced adsorption capacity of PFAAs in the sorption barrier, particularly for the longer chain PFAAs. This study highlights the importance of accounting for the competitive sorption among the PFAAs and co-contaminants (e.g., CEs) during the implementation of adsorptive barriers. Moreover, this work provides encouraging proof-of-concept data supporting the potential development and application of coupled biological and sorptive systems for the in situ remediation of groundwater contaminated with a mixture of PFAAs and CEs.