Utilization of desalination wastewater for SO_x, NO_x, and CO₂ reduction using NH₃: Novel process designs and economic assessment

Many countries discharge considerable amounts of desalination wastewater directly into the ocean, which cause environmental pollution, destruction of ecosystems, and economic losses. Desalination wastewater contains valuable metal ions such as Na⁺, Ca²⁺, and Mg²⁺, which react with carbonate and sulfate ions; therefore, it has the high potential to reduce the NO_x, SO_x, and CO₂. Thus, this study designed process for the utilization of desalination wastewater to capture and utilize NO_x, SO_x, and CO₂ using NH₃. A process model was developed, which was composed of following three steps: (1) metal ion separation in desalination wastewater based on pH swing processes for separating Ca²⁺ and Mg²⁺ as Ca(OH)₂ and Mg(OH)_2, respectively; (2) NO_x capture and SO_x capture and utilization using generated Mg(OH)₂, and (3) CO₂ capture and utilization using NH₃. Subsequently, to demonstrate the economic validity of the suggested process, an economic assessment was conducted and total annualized costs (TACs) of the conventional and proposed processes were compared. As a result, ~96 % of NO_x was captured, the SO_x capture efficiency was 99 %, and ~94.7 % of CO₂ was captured. Thus, a reduction of 11.2 % in the TAC was achieved using the proposed process, indicating its high economic feasibility.