Application of a three-stage remediation process to cleanup petroleum-hydrocarbon contaminated sediments

Abstract

Sediments are usually the sinks for many waterborne pollutants, and thus, contaminated sediments need to be remediated to prevent the release of pollutants into the water bodies. The objective of this study was to develop a three-stage system to cleanup total petroleum hydrocarbons (TPH)-contaminated sediments. Sediments were collected from the Kaohsiung harbor with a TPH concentration of 8,105 mg/kg. Results from the sediment analyses show that sediments were mainly fine-grained silts, and the sediment organic matter content was about 19%. Thus, the surfactant washing method became an optimal option for the cleanup of TPH-contaminated sediments at this site. The three-stage scheme included the river water (RW) washing stage followed by the surfactant (Triton X-100) washing and Fenton-like oxidation stages. Batch experiments were conducted to evaluate the TPH removal efficiency by RW washing and surfactants washing with initial Triton X-100 concentrations of 0.5, 1, and 5% (w/w). In these oxidation experiments, three different hydrogen peroxide (H2O2) concentrations (0.6, 1.05, and 6 vol.%) were used to evaluate the TPH oxidation efficiency. Based on the results of the batch experiments, the three-stage operational process was performed using the optimal conditions from the batch experiments. The three-stage process was performed using 10 pore volumes (PVs) of RW washing followed by 30 PVs of Triton X-100 (0.5%) washing and 20 PVs of hydrogen peroxide (6%) oxidation. Results show that approximately 6% of TPH was removed after the RW washing stage. Up to 71% of TPH was removed by surfactant washing through mobilization and solubilization mechanisms. Approximately, 8% of TPH was removed through the Fenton-like oxidation, and a total of 86% of TPH was removed after the three-stage processes. This implies that the Fenton-like oxidation could be used as a polishment method for the TPH-contaminated sediment treatment. Results indicate that the proposed sediment treatment scheme could provide an efficient and cost-effective alternative for TPH-contaminated sediment remediation.