Determining the Optimal Treatment for Contaminated Dredged Sediment using MCDA and LCA

Abstract

Contaminated sediments that have been dredged are impacted by industrial, agricultural, and urban activities, and present health and environmental risks due to pollutants like Potentially Toxic Elements (PTEs) and organic pollutants. Treatment methods are crucial, as after the dredging process, one end of the life point is the disposal of the sediment back into the sea. If the sediment is not treated for TBT, the current regulation dictates that the sediment must be disposed of in landfills, of which availability is more scarce compared to the sea. The study provides guidance on selecting sustainable sediment treatment methods that balance environmental impacts and organic pollutant removal. This study evaluated four sediment treatment methods: Fenton + Photoelectrocatalysis (PEC), Fenton at pH 3, Methanol + Ultrapure Water + PEC, and Density Separation + PEC. The evaluation uses a Comparative Life Cycle Assessment (CLCA) and Multi-Criteria Decision Analysis (MCDA). The goal of the study is to determine the most sustainable treatment method to remove tributyltin (TBT) from 1 ton of dredged sediment. The results indicate that the treatment method including the Fenton process, particularly Fenton + PEC, achieves high TBT removal, but generates environmental impacts due to energy and chemical use, with hydrogen peroxide production being a major contributor. Methanol + Ultrapure Water + PEC is impactful due to the production of methanol; this contributes to Eutrophication. Density Separation + PEC shows the lowest environmental impact, driven mainly by salt usage and resulted in the most sustainable option according to the MCDA results. Improvement points include using renewable energy, process integration, and closed-loop systems for better recourse efficiency and process development.