Biochemical ripening of dredged sediments. Part 2. Degradation of polycyclic aromatic hydrocarbons and total petroleum hydrocarbons in slurried and consolidated sediments

Abstract

Ripening of polycyclic aromatic hydrocarbons (PAH) and total petroleum hydrocarbons (TPH) polluted dredged sediment can be considered as a bioremediation technique. Aerobic biodegradation of PAH and TPH was studied in five previously anaerobic-slurried sediments during a 350-d laboratory incubation experiment. In addition, oxygen penetration and degradation of PAH and TPH were studied in three consolidated (physically ripened) sediments. All experiments were conducted in the laboratory at 30 degrees C. A double exponential decay model could adequately describe PAH and TPH degradation kinetics in the slurried sediments. First-order degradation rate constants for the rapidly degradable fractions (12-58%) were approximately 0.13 and 0.058 d(-1) for PAH and TPH, respectively, whereas the rate constants for the slowly degradable fractions were approximately 0.36 x 10(-3) (PAH) and 0.66 x 10(-3) d(-1) (TPH). Rate constants for the rapidly and slowly degrading fractions have the same order of magnitude as the mineralization rate constants of the rapidly and slowly mineralizing organic matter (OM) fractions in the sediments. Oxygen uptake by degradation of PAH and TPH was negligible compared to the oxygen uptake by sulfur oxidation and OM mineralization. In consolidated sediments, PAH and TPH degradation was limited to the oxygenated part. Amounts of PAH and TPH that degraded in the oxygenated parts of the consolidated sediments during 21 d of incubation were similar to the amounts that degraded during 21 d in the slurried sediments.