Application of a biosurfactant in naphthalene, phenanthrene, and TCE remediation

A nonsterile biological process to produce a biosurfactant utilizing used vegetable oil was developed. The microorganism used was a Pseudomonas sp. The biosurfactant was used to evaluate the solubilization, adsorption onto soils, and biodegradation of the selected NAPL (Nonaqueous Phase Liquid) compounds, naphthalene, phenanthrene, and TCE (Trichloroethylene). The performance of the biosurfactant was compared to that of SDS (Sodium Dodecyl Sulfate) and Triton X-100, two commercially available chemical surfactants.; The biosurfactant produced utilizing used vegetable oil as the sole substrate lowered the surface tension of the broth to 28 mN/m. A solid biosurfactant was obtained by adding NaOH into the broth to form precipitate and subsequent isopropanol washing of the precipitate. The biosurfactant product had a CMC of 0.2 g/L and lowered the surface tension of water to 29 and 25 at pH values of 11 and 7, respectively. The naphthalene solubilization capacity of this biosurfactant was comparable to that of Triton X-100 and SDS.; The surfactants, at aqueous concentrations above CMC, effectively decreased the adsorption of naphthalene and phenanthrene by kaolinite clay and organic mulch. A model was developed to describe the effect of surfactants on the adsorption of target compounds. Model calculations showed that surfactant molecules that were sorbed onto soils could modify the adsorption capacity of the adsorbent as indicated by the effectiveness factor. The effectiveness factor increased with surfactant concentration and reached a limiting value. Calculations of data in the literature were also performed and similar results were obtained.; The biodegradation study showed that naphthalene solubilized by the biosurfactant and Triton X-100 was available to biodegradation. Naphthalene, up to 200 mg/L in the biosurfactant solution and 600 mg/L in Triton X-100 solution, was biodegraded. In contrast, SDS, at the concentrations investigated (2–10 g/L), totally inhibited the biodegradation of naphthalene by the Pseudomonas sp . The biosurfactant supported microbial growth while Triton X-100 did not. No biodegradation of TCE was observed for 3 weeks at TCE concentration of 10 mg/L.