Evaluation of various pretreatments of surface water for ion exchange demineralization in industrial applications

Abstract

This study evaluates pretreatment strategies before ion exchange demineralization for producing high-quality demineralized water from surface water in industrial applications. It focuses on water quality improvements and compares the treatment system's resource efficiencies (water, energy, CO₂-equivalent emissions and costs). Four pretreatment methods were examined: (Scenario 0) an existing system using coagulation/flocculation and sandfiltration, (Scenario 1) the addition of a scavenger resin to the existing system to improve organics removal, (Scenario 2) employing biologically activated carbon filtration (BACF) and scavenger resin as a chemical-less alternative, and (Scenario 3) application of BACF with ultrafiltration (UF) barrier. Two of the four scenarios achieve the required water qualities (i.e., TOC ≤ 0.2 mg/L): Scenario 1 and 3. BACF and UF (Scenario 3) showed the best water quality achievements; both technologies complement each other regarding removing organic fractions. Water efficiencies between 93 % (Scenario 2) and 97 % (Scenario 0) can be achieved, where the sludge-water return is crucial, particularly for Scenario 3. CO₂-equivalent emissions, combining energy, materials and chemicals used, but also costs, are consistently increased by adding enhanced pretreatments. Specific emissions and estimated costs are slightly lower for Scenario 3 (0.7 kg_CO2-eq/m³_Prod, 1.4 €/m³_Prod) than Scenario 1 (0.8 kg_CO2-eq/m³_Prod, 1.5 €/m³_Prod).