Remediation of contaminated marine sediments: assessment and comparison between different treatment

The remediation of contaminated marine sediments represents a critical challenge, due to the complex interactions between pollutants, sediment matrices, and site-specific conditions. Traditional approaches often focus primarily on contaminant removal efficiency, overlooking the broader environmental implications associated with remediation processes. In this context, the present PhD research aims to evaluate and compare different treatment technologies for contaminated marine sediments, with a specific focus on both their effectiveness and environmental sustainability. The study investigates three remediation approaches based on distinct mechanisms: sediment washing, chemical oxidation, and mycoremediation. Experimental activities were conducted at laboratory scale using sediments contaminated mainly by petroleum hydrocarbons. The performance of each treatment was assessed through the analysis of Total Petroleum Hydrocarbons (TPH) removal efficiency, as well as through ecotoxicological evaluations, including phytotoxicity tests, to determine the residual environmental impact of the treated sediments. The results demonstrate that sediment washing is particularly effective in enhancing the removal of hydrocarbons, especially when optimized surfactant systems are employed, although its performance is strongly influenced by sediment properties. Chemical oxidation showed high potential for rapid contaminant degradation, with oxidizing agents such as potassium ferrate and permanganate achieving significant reductions in TPH concentrations. However, the process requires careful control of operating conditions to avoid undesired alterations of the sediment matrix. Mycoremediation, based on fungal activity, proved to be a promising biological approach, capable of progressively degrading hydrocarbons while maintaining a lower environmental impact, despite longer treatment times. A key contribution of this work is the integration of conventional performance indicators, highlighting that contaminant removal alone does not necessarily correspond to an improvement in sediment quality. To address this limitation, an environmental sustainability index was developed and applied to the investigated technologies. The index incorporates multiple indicators, including environmental benefits, resource consumption, and indirect impacts, allowing for a systematic comparison of different treatment options. The application of this index revealed significant differences among the technologies, underlining the trade-offs between efficiency and sustainability. The findings of this research highlight the importance of adopting integrated and multi-criteria approaches in the selection of sediment remediation strategies. Rather than relying solely on contaminant removal efficiency, decision-making processes should consider environmental sustainability as a key parameter. This work provides both experimental insights and methodological tools that can support the development of more effective and sustainable remediation solutions for contaminated marine sediments.