Biodegradation of dispersed diesel fuel under high salinity conditions

Petroleum products such as diesel fuels may be released into the marine or coastal environment by discharges of ballast and bilge waters, dry dock activities, and tanker and non-tanker accidents. In addition to containment and recovery of spilled petroleum products, the treatment of seawater in a spilled area may be needed in order to reduce potential damages to aquatic organisms and their habitats. This paper reports on a laboratory study which evaluates the biodegradation efficacy of a dispersed diesel fuel under high salinity conditions using an aerobic, upflow submerged biofilter coupled with a trickling filter, which is used to capture and treat volatile organic compounds (VOCs) escaped from the biofilter caused by aeration. The experimental data indicate that total organic carbon (TOC) is removed with >90% efficiency in the biofilter at a feed TOC concentration of 1000 mg/l and a volumetric loading of 1.5 kg TOC/m 3-day. A first-order kinetic equation is developed to describe the observed TOC removal in the biofilter, and the first-order rate constant is estimated as 0.17 h −1. Moreover, under the conditions tested VOCs account for approximately 8% of the diesel fuel fed to the biofilter. The trickling filter is capable of removing 68% of VOCs captured at an empty bed retention time of 10 s.