Soil washing process enhanced by surfactants is becoming a promising technique in removing polycyclic aromatic hydrocarbons (PAHs, a group of compounds with high potential toxicity) from soil; it has been widely used due to its cost-effective characteristic and high pollutant removal efficiency. However, this approach needs a large amount of extracting solvents and leads to a large quantity of effluents which contain PAHs with high concentrations. Further treatments on the effluents must be conducted for water reclamation. A simultaneous adsorption and biodegradation (SAB) approach was developed to remove PAHs from soil washing solution (SWS) by immobilizing a pyrene-degradable bacterium (Mycobacterium strain) in polyvinyl alcohol-sodium alginate (PVA-SA) hydrogel beads. The SWS was obtained by treating a heavily contaminated soil from a coking plant in Beijing, China, with 4 g/L Triton X-100 (TX100) which is a nonionic surfactant. Six treatments including free bacteria (1), blank PVA-SA bead (2), degrading bacteria at low (3), medium (4) and high (5) initial concentrations immobilized in PVA-SA bead, plus a special PVA-SA bead with immobilized degrading bacteria at a medium concentration and NaN3 (6) were used to three solutions (i.e., phenanthrene (PHE), phenanthrene dissolved in 4 g/L TX100 (PTX) and soil washing solution (SWS)). Our observations showed that hydrogel beads with immobilized bacteria can remove almost 100% phenanthrene from PHE and PTX solutions (800 ng/mL) after 24 h and 72 h, and 75% ∑16PAHs (1000 ng/mL) from SWS in 96 h, respectively. The beads after using were filtered and reused to treat the contaminated solutions again; the time needed for a removal efficiency of over 90% gradually decreased since bacteria have acclimated. Our data also showed that the bead provided protection for bacterial cells against toxic substances such as TX100. These findings suggest that hydrogel beads with immobilized bacteria are more effective, efficient and sustainable than free bacteria and blank bead due to simultaneous adsorption and biodegradation processes.

Simultaneous adsorption and biodegradation of soil washing solution containing PAHs with high concentrations by degrading bacteria immobilized in PVA-SA hydrogel beads

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.