Effect of Sediment on the Biodegradation of Petroleum Contaminants in Natural Water

Biodegradation of petroleum contaminants in natural water was studied within an Asian river context where high-suspended sediment content exists. Petroleum contaminant is one of the main pollutants in the Yellow River; at the same time, there is a high sediment content in the river system. This research highlighted the effect of sediment on the biodegradation of petroleum contaminants, as well as the related mechanisms regarding the effect. Biodegradation of petroleum contaminants was studied under different sediment contents. The distribution of petroleum contaminants in water and sediment phases as well as the relevant biodegradation kinetics were also investigated. The results showed that in water system with the sediment content of 0.5 g/L, about 84% of petroleum contaminants with the initial concentration of 11.64 mg/L could be degraded after incubation for 63 days at 20°C. It was also indicated that the presence of sediment exerted significant influences on the biodegradation of petroleum contaminants in water system, and the influences were different from one cultivation stage to another. In the first stage, the biodegradation rate was higher in the water system with sediment than in that without sediment. In the second stage, the biodegradation rate was lower in the former than in the latter. In the last stage, the biodegradation rate was higher in the water system with sediment than in that without sediment. The presence of sediment could stimulate the growth of petroleum contaminant-degrading bacteria. Moreover, about 90% of the contaminants and bacteria were attached on the sediment. The sorbed contaminants on sediment could also be biodegraded by bacteria. The biodegradation of contaminants in water and sediment phases all fit well with the first-order kinetics, and the biodegradation rate constant in water phase was higher than that in sediment phase. However, as the contaminant concentration at the sediment phase was much higher than that in water phase, the biodegradation of petroleum contaminants mainly occurred at the sediment phase.