Evaluation of water hardness treatment methods using sodium hydroxide and their impact on water quality

Hard water is an environmental and technical challenge caused by high concentrations of calcium (Ca²⁺) and magnesium (Mg²⁺) ions, leading to scale formation that affects the efficiency of household and industrial appliances and increases maintenance and treatment costs. Additionally, hard water can pose health risks and reduce its quality for daily use. This study aims to evaluate the effectiveness of different doses of sodium hydroxide (NaOH) in treating water hardness and improving water quality by reducing total hardness (TH) and adjusting the physicochemical properties of water. Three main dosages were tested: the first dosage (5 g/L of NaOH), which assessed the basic effectiveness of sodium hydroxide; the second dosage (2.5 g/L of NaOH and 2.5 g/L of Na₂CO₃ with HCl and acid), aimed at balancing hardness reduction with mineral retention; and the optimized dosages (10, 20, and 30 mg/L of NaOH), which proved to be the most effective and balanced. The optimized doses successfully reduced total hardness to levels compliant with Algerian standards while maintaining calcium and magnesium concentrations within acceptable ranges. Furthermore, electrical conductivity (EC) remained within safe limits without significant increases, ensuring the water did not become oversaturated with dissolved salts. The slight increase in sodium (Na⁺) concentration also remained within permissible levels, enhancing the water's suitability for drinking and other uses. Based on these results, the optimized NaOH dosages are the optimal solution for water hardness treatment, achieving a balance between reducing hardness and ensuring water quality in compliance with local standards.