Batch tests for the optimization of PAH bioremediation in Mediterranean tourist port sediments

Port sediments are frequently contaminated by organic or inorganic pollutants, among which polycyclic aromatic hydrocarbons (PAHs) represents a serious hazard for humans and ecosystems involving the need to treat them before disposal. In the framework of the ENPI MAPMED project (Management of port areas in the Mediterranean Sea basin), the present work aims to evaluate the best conditions of PAHs bioremediation by comparing in slurry aerobic batch tests: bioaugmentation, nutrients and different surfactants addition (saponins, Tween 80). Sediments were collected from the ports of El Kantaoui (Tunisia) and Cagliari (Italy). Fluorene, phenanthrene, fluoranthene, pyrene and benzo(a)pyrene were added at the concentration of 40mg/kgss. Parallel abiotic tests were performed. The experiments conducted without amendments showed in both sediments, after 5 days, complete fluorene and phenanthrene degradation, while pyrene and fluoranthene degradation was slower and showed a 3-day lag phase. Moreover, fluoranthene was not completely removed after 10d. Benzo(a)pyrene was only removed of about 20% in El Kantaoui sediments. Regarding the amendments, the best results were obtained with nutrient regulation (C:N:P ratio 100:10:1) and bioaugmentation, which increased removal rates and reduced the lag phase for fluoranthene and pyrene, in both sediments. Benzo(a)pyrene removal was only slightly increased in Cagliari sediments. The effect of the two surfactants differed: phytogenic saponins affected positively PAHs removal while synthetic Tween80 gave only a slight improvement in El Kantaoui sediments; for Cagliari sediments the effect of both surfactants was negative. These results are in line with previous observations suggesting a strong dependence on the specific sediments properties.