## 4 Discussion  
The handling of dredged sediments depends on the level of contamination and local regulations, as specific restrictions, costs and treatment requirements may apply [39]. The most common management practices for dredged sediments include landfilling and deep-sea disposal [5], and metal extraction and natural recovery [49]. However, increasingly stricter environmental legislation affects both the availability of landfilling space and the cost of utilizing it. One example is the European Landfill Directive (1999/31/EC), which has caused some landfills to close, resulting in a reduction in the space available for landfill, and higher landfilling costs [5]. Consequently, stakeholders involved in dredged sediment management are increasingly motivated to investigate alternatives to landfilling. Stabilization and solidification methods, which enable the use of dredged materials in construction, is a common strategy internationally [50]; however, its use is limited in different countries, due to geological conditions (soft clays), high salinity and limited knowledge. Stabilization may be more sustainable when combined with a method where metals are extracted from the sediment before it is stabilized. The extraction of metals from sediment can be performed using biological, physical or chemical techniques, which can either be used independently or combined [3; 50]. However, ASEC technology obtains solids with humidity below 1%. For the current experiment, the annual production of solids would generate 99.6 tons of dried solids for the treatment of Rio Tinto, 110 tons for Tharsis, and 250 tons for dredged material treatment. The stabilization is instantaneous without the addition of reagents (cost-effective). This is translated as a reduction in storage and transport costs, but it also offers an advantage to concentrate the dissolved elements for secondary mining processing (re-exploitation). In addition, this removal implies the cessation of pollution discharge into aquatic systems, thereby enhancing the ecosystem services provided by these aquatic bodies. Apart from the production of cleaner sediment, another potential benefit of metal extraction is the opportunity to recover valuable metals, thereby reducing the need for mining. Once elements have been extracted from the sediment, the environmental risks of residual sediments are reduced, and management criteria are more likely to be met [51]. Included in these elements are the CRM and other elements of commercial interest, so the extractive process of solid crystallized salts might present a dual economic advantage in terms of re-mining and re-exploitation of resources alongside removal. As an overview, based on some elemental concentrations found in the solid samples' by-products and the current market price [40; 41; 52; 53; 54; 55], an estimation of the maximum economic potential value was calculated as annual gross production considering an interrupted deprivation cycle working for a daily treatment of 10 m\({}^{3}\), with 100% of the extracted element recovered. But also, the estimation accounted for a reduction in extractive expenses and partial recovery (70%), and energy consumption expenses (0.13 USD/kWh for a system of 20 kWh/d) were discounted to estimate the net production obtained (Table 2). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Annual Production (kg)**} & \multicolumn{3}{c}{**Annual Potential Revenues (kUSD)**} \\ \hline  & **Rio Tinto** & **Tharsis** & **Dredged Mat.** & **Rio Tinto** & **Tharsis** & **Dredged Mat.** \\ \hline Al & 2422 & 3005 & 3074 & Al & 5.409 & 6.710 & 6.864 \\ \hline As & 11.62 & 1.91 & 29.00 & As & 2.022 & 0.332 & 5.045 \\ \hline B & 1.217 & 3.058 & 7.614 & B\({}_{2}\)O\({}_{3}\) & 3.652 & 9.173 & 22.84 \\ \hline Ba & 0.244 & 2.227 & 27.682 & Ba & 0.000 & 0.000 & 0.005 \\ \hline \hline \end{tabular}
\end{table}