Enhancing bioavailability in aquatic sediments using ultrasound

A significant fraction of organic material in aquatic sediments is associated with the particulate phase, which have been shown in numerous studies to sequester toxic contaminants. Most treatment technologies designed for the removal of toxic contaminants from aquatic sediment are strongly influenced by the availability of the contaminant in the aqueous phase. This is especially true when bioremediation of contaminated sediment is considered since microorganisms are capable of utilizing only soluble organic substrate. Hence for microbial utilization of any organic contaminant associated with the particulate phase, the rate-limiting step is often the solubilization phase during which the contaminants are made bioavailable in the soluble phase. In this study the use of ultrasound energy is investigated as a pretreatment step to enhance the bioavailability of contaminants sorbed on to aquatic sediments. Experiments were conducted using an extensively contaminated aquatic sediment obtained from Newton Creek in New York as the test material. Desorption studies were conducted by sonicating the sediment at varying sediment solids concentrations, sonication energies and duration of sonication. Results from this study indicate that sonication of sediment suspensions can significantly enhance the release of organic matter into the soluble phase. Particle size distribution of the sediment matrix was also significantly altered after sonication. It was also found that the rate and extent of anaerobic biodegradation of organic material associated with the particulate phase was significantly greater when sediment suspensions were sonicated prior to biodegradation.