Recycling CaCO_۳ in Desalination Post-Treatment and in Water Salinity Reduction by Reacting Rejected Brine Water (RBW) with Both Ca(OH)_۲ and CO_۲

Desalination plants have expanded considerably over the last decade, as the need for drinking water increases with population growth. The handling of brine from desalination processes entails serious environmental concerns for many plants and is associated with rising costs. Direct brine discharge has the potential to alter local marine environments, as increased salinity presents a substantial risk to marine ecosystems. It is therefore necessary to develop methods to recover this brine before it is disposed of, to reduce its harmful impact on the environment, and to produce valuable commercial chemical products. Indeed, this study adopts a two-pronged approach. The first focuses on valorizing Rejected Brine Water (RBW) from a desalination plant to produce valuable chemical products such as calcium carbonate (CaCO₃) and sodium carbonate (Na₂CO₃), while also reducing water salinity to help protect aquatic ecosystems. The second approach consists of reusing and recycling the prepared CaCO۳ recovered in the first step for osmosis water remineralization (permeate) inside the desalination plant (post-treatment). As a result, our first study shows that valorization of RBW by adding portlandite solid (Ca(OH)۲) and carbon dioxide flow gas (CO۲) leads to CaCO۳ precipitation; the mass of the recovered CaCO۳ increases proportionally with that of the added reagents. High CO۲ flow rates lead to a remarkable reduction in the salinity of RBW. As an application, the produced salt CaCO۳ was charged in a pilot calcite bed at laboratory scale in order to carry out the second step of this study. The obtained results show that remineralization using recovered CaCO۳ could correct the calco-carbonic balance of osmosis water, and achieve the drinking water standard; but that is linked to many parameters, such as CO۲ flow rate, speed of permeate water, and the thickness of the bed, which have a huge effect on the process.

کلیدواژه ها:

Desalination ، RBW management ، CaCO۳ precipitation ، lime ، Carbon dioxide ، Remineralization ، salinity reduction