Influence of surfactant enhanced remediation on transport behaviors of pollutant-degrading bacteria in porous media containing nonaqueous-phase liquid.

Surfactant-enhanced remediation (SER) combining with in-situ bioremediation via injection of pollutant-degrading bacteria into contaminated aquifer has recently attracted great attentions due to the high efficiency for the removal of non-aqueous phase liquid (NAPL) contamination from aquifer. However, the effects of SER on the transport and adhesion of NAPL-degrading bacteria in NAPL contaminated-porous media are not well understood. This study investigated the effects of SER on the transport/deposition of NAPL-degrading bacteria (Acinetobacter lwoffii U1091) in porous media containing NAPL under both 5 mM and 50 mM NaCl solution conditions. Three typical cationic, anionic, and non-ionic surfactants namely cetyltrimethylammonium bromide (CTAB), sodium dodecyl benzene sulfonate (SDBS), and triton X-100 (TX-100) with different concentrations (i.e. 100, 400, and 600 mg/L) commonly used to extract NAPL from aquifer were employed to simulate SER processes. We found that SER employing different types of surfactants exhibited different influence on the transport and deposition of bacteria in NAPL-contaminated porous media. Through decreasing the energy barrier between bacteria and porous media, CTAB-enhanced remediation could increase bacterial deposition in NAPL-contaminated porous media. In contrast, both SDBS- and TX-100-enhanced remediation processes could reduce bacteria deposition in NAPL-contaminated porous media due to the enhanced repulsion between bacteria and porous media. These results demonstrated that the SER process had great impact on the transport behavior of NAPL-degrading bacteria in porous media, which would eventually affect the efficiency of subsequent in-situ bioremediation process.