Effectiveness of reducing Ca–Mg hardness using NaOH precipitation, in Ghardaïa groundwater

Bouamer, Kheira; Boukhari, Hamed; Mansouri, Khaled

doi:10.22098/mmws.2025.18308.1679

Effectiveness of reducing Ca–Mg hardness using NaOH precipitation, in Ghardaïa groundwater

مقالات آماده انتشار

نوع مقاله : Special Issue: New Approaches to Water and Soil Management and Modeling

نویسندگان

¹ Laboratory of Materials, Energy Systems Technology and Environment, Université de Ghardaia, Ghardaia, Algeria

² Department of Process Engineering, Faculty of Science and Technology, Mathematics and Applied Science, Ghardaïa University, Ghardaïa, Algeria

10.22098/mmws.2025.18308.1679

چکیده

In Saharan regions, ensuring fresh water to consumers is very difficult, as the predominant source is groundwater loaded with mineral salts from reservoir rocks. The study is based on the choice of caustic soda (NaOH) as a treatment element by chemical precipitation. The protocol followed includes treatment with different doses of NaOH: (500 mg/L of NaOH), (250 mg/L of NaOH and 250 mg/L of Na₂CO₃ adjusting once with acetic acid CH₃COOH and another time with hydrochloric acid HCl), then optimized doses of NaOH alone. The results are then examined, on the one hand, on the reduction of hardness (TH) and, on the other hand, on its impact on pH, electrical conductivity (EC) and salinity. The results indicate that the first dose significantly reduces permanent calcium and magnesium hardness (TH) from 558 mg/L exceeding (Algerian standard limited 500 mg/L) to 328 mg/L, with increases in pH exceeding the potability threshold, while treatment with sodium hydroxide and sodium carbonate are effective in reducing or even eliminating Ca²⁺ and Mg²⁺ ions, but there is still a strong increase in alkalinity. The solution is adjusted by an acid still presents additional effects such as solubility of salts and therefore the need to adjust the electrical conductivity (EC). Finally, the treatment is optimized at a low dose of NaOH (20 mg/L) without the addition of sodium carbonate. This dose has proven to be the most adequate, thus allowing a substantial reduction in TH (615 reaching 400 mg/L) while balancing the pH and electrical conductivity (EC) parameters. These results demonstrate the effectiveness of NaOH in the treatment of hard water, while keeping control of its influence on other parameters such as sodium (225.77 mg/L of Na+) where it presents an increase of up to 10%, although it is a significant increase, it is found that the waters of the region exceed this dose in their natural state. Overall, the experience still offers promising and practical solutions for domestic, agricultural and industrial applications and guaranteeing compliance with water quality standards.

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