Effect of surfactant addition on phenanthrene biodegradation in sediments

Abstract

A laboratory study was conducted to determine whether commercial surfactants enhance the bioremediation of PAH‐contaminated sediments. Phenanthrene was chosen as a representative PAH; an inoculum of PAH‐degrading microorganisms, enriched from an aquatic sediment, was used in sediment‐water slurry microcosm biodegradation experiments. Of seven nonionic surfactants tested, only one (Triton X‐100) did not inhibit phenanthrene mineralization at concentrations above the critical micelle concentration (CMC). Temporal studies on Triton X‐100 revealed that while it initially inhibited mineralization in sediment‐free microcosms, after 1 week Triton X‐100 slightly improved phenanthrene biotransformation and mineralization in microcosms with and without sediment. For all treatments, phenanthrene disappearance was complete after 9 d, and mineralization reached 50 to 65% after 12 d. Sorption to the sediment appears to have reduced the free aqueous surfactant concentration, thereby reducing surfactant toxicity to the microorganisms. These results suggest that many surfactants are toxic to PAH‐degrading microorganisms, and while surfactant addition may not always have adverse effects on biodegradation, the use of surfactants might not be desirable to achieve complete contaminant removal.

Use of biosurfactant to remediate phenanthrene-contaminated soil by the combined solubilization–biodegradation process

“…In the case of microorganisms degrading hydrophobic hydrocarbons, the presence of surfactants, especially in concentrations above the CMC, has had an inhibiting effect [24][25][26]. Although this phenomenon may be partly explained by the reduced availability of micellar hydrocarbons [27,28], inhibition was also observed for hydrophilic substrates.…”

Solubilization of pyrene by anionic?nonionic mixed surfactants

“…A few studies have also indicated the potential for using micellar solubilization to clean up residual and sorbed contaminants from soils [10][11][12][13][14]. Surfactant may also improve microbial remediation of HOCs in soils by affecting the accessibility of the HOCs to microorganisms [15][16][17][18][19][20].…”

“…Many microorganisms, including bacteria, algae, and fungi, have been shown to possess degradative enzymes for the oxidative degradation of PAHs [34], however, the in situ microbial degradation of PAHs is limited by their low bioavailability. Various surfactants have been employed with attempts to increase the aqueous-phase concentrations of PAHs, and thus the bioavailability [4,8,17,18]. Removal of PAHs from contaminated soils and groundwater by surfactants is governed mainly by the micelle and/or microemulsion concentrations of surfactants to solubilize or mobilize the pollutants.…”

Removal of Benzo[a]pyrene by a fungus Aspergillus sp. BAP14

“…In general, surfactants can increase the solubility of PAHs in the culture medium to increase their bioavailability. Studies have been reported that surfactants can enhance biodegradation percentage (Arosetin and Alexander 1992;Thiem 1994), while others have found that applying surfactants inhibits biodegradation due to the alteration of the interactions between the cells and the substrate (Stelmack et al 1999) or the toxicity of surfactants themselves (Colores et al 2000;Tsomides et al 1995;Volkering et al 1995;Kawai et al 1997). It was observed from our experiments that surfactants could enhance the solution of BaP, but they did not improve the degradation percentage of BaP.…”