Degradation of polycyclic aromatic hydrocarbons in the presence of synthetic surfactants

TLDR

The biodegradation of polycyclic aromatic hydrocarbons (PAH) is limited by their low water solubility and dissolution rate. Nonionic surfactants and sodium dodecyl sulfate increase PAH solubility, but SDS also inhibits degradation by acting as a preferred growth substrate; alkylethoxylate and alkylphenolethoxylate surfactants are toxic to PAH‑degrading microbes, with toxicity decreasing as ethoxylate chain length increases, while nontoxic surfactants enhance degradation of fluorene, phenanthrene, anthracene, fluoranthene, and pyrene.

Abstract

The biodegradation of polycyclic aromatic hydrocarbons (PAH) often is limited by low water solubility and dissolution rate. Nonionic surfactants and sodium dodecyl sulfate increased the concentration of PAH in the water phase because of solubilization. The degradation of PAH was inhibited by sodium dodecyl sulfate because this surfactant was preferred as a growth substrate. Growth of mixed cultures with phenanthrene and fluoranthene solubilized by a nonionic surfactant prior to inoculation was exponential, indicating a high bioavailability of the solubilized hydrocarbons. Nonionic surfactants of the alkylethoxylate type and the alkylphenolethoxylate type with an average ethoxylate chain length of 9 to 12 monomers were toxic to a PAH-degrading Mycobacterium sp. and to several PAH-degrading mixed cultures. Toxicity of the surfactants decreased with increasing hydrophilicity, i.e., with increasing ethoxylate chain length. Nontoxic surfactants enhanced the degradation of fluorene, phenanthrene, anthracene, fluoranthene, and pyrene.