Kinetic Modeling for a Novel Permeable Reactive Biobarrier for In Situ Remediation of PAH-Contaminated Groundwater

Abstract

Permeable reactive barriers (PRBs) are an environmentally friendly and cost-effective in situ remediation technology that have been used to restore polycyclic aromatic hydrocarbon (PAH)-contaminated groundwater. However, the understanding of removal mechanisms of the pollutant from groundwater remains a challenge due to the complex interactions between microbial evolution, organic carbon kinetics, and multiple chemical reactions. In this study, a one-dimensional reactive transport model was developed to study 450-day column experiments for removal of phenanthrene from groundwater using new PRB materials A (including wheat straw) and B (including coconut shell biochar). The modeling results provided a deeper understanding of the removal process for phenanthrene, and showed that Material B had a higher removal efficiency than Material A over 34 days. The removal efficiency of phenanthrene in both Materials A and B was close to 100% in the PRB system. This was because (1) Material B had a higher adsorption capacity for phenanthrene than Material A, and adsorption played an important role in the short term (e.g., 20 days), whereas biodegradation controlled longer-term removal processes; (2) the biomass in Column B was higher (p<0.05) than that in Column A; and (3) Column B had a higher microbial yield coefficient that could favor longer-term microbial growth and biodegradation activity. Material B might have greater potential than Material A for longer-term remediation performance. The simulated results generally were in agreement with the experimental results and support the development of field-scale pilot testing of these materials for groundwater remediation.