INFLUENCE OF SUSPENDED SEDIMENT ON THE BIODEGRADATION OF CHLORINATED DIBENZO-P-DIOXINS

Little is known of how the uptake and degradation of highly hydrophobic compounds, such as polychlorinated dibenzo-p-dioxins (PCDDs), by microorganisms is influenced by sorption of these compounds to sediment. In this study aqueous solutions of a mixture of 2-chloro-, 1,3-dichloro-, 2,8-dichloro- and 1,2,4-trichlorodibenzo-p-dioxins were first incubated for 24 days with 100 mg/l suspended sediment. Subsequently, the degradation of the PCDDs in these sediment suspensions by Alcaligenes sp. strain JB1 was compared to that in solutions which did not contain sediment. The amounts of all four compounds degraded in the sediment suspensions after 168 b were greater than those initially present in the dissolved phase, based on their calculated sediment-water partition coefficients. The sorbed fractions were therefore sufficiently readily desorbed to be partly degraded. However, the biodegradation rates were lower in the sediment suspensions than in the solutions.