Water 2022, 14, 3422. https://doi.org/10.3390/w14213422 www.mdpi.com/journal/water Article Removal of Sulphate Ions from Borehole Water Using Nanofiltration and Reverse Osmosis Boukary Sawadogo *, Yacouba Konaté, Seyram Kossi Sossou, Nana Fassouma Ado Saidou, Abdoul Wahab Nouhou Moussa and Harouna Karambiri Institut International d’ingénierie de l’Eau et de l’Environnement (2iE), Laboratoire Eaux Hydro‐Systèmes et Agriculture (LEHSA), 1 Rue de la Science 01, Ouagadougou 01 BP 594, Burkina Faso * Correspondence: boukary.sawadogo@2ie‐edu.org Abstract: Consumption of contaminated water poses health hazards to humanity and hence in‐ creases the need for treatment. An excessive level of sulphate in borehole water was detected in the drinking water supply of Garpéné village in Burkina Faso. This study aimed to evaluate the perfor‐ mance of nanofiltration and reverse osmosis for the removal of sulphate ions from borehole water. A combined nanofiltration and reverse osmosis pilot was used for the treatment of the raw borehole water and some prepared synthetic solutions. Different experimental conditions were used to eval‐ uate the effects of the pressure, the nature of the solution to be filtered, and the ions accompanying the sulphate. The filtration tests were conducted at transmembrane pressures of 1, 2.5 and 4 bar with a nanofiltration NF270 membrane and at transmembrane pressures of 4, 6 and 8 bar with a reverse osmosis TW30 membrane. The membrane used were a thin‐film composite (TFC) membrane from Filmtec. The pilot was fed with real water from the Garpéné borehole and synthetic solutions of calcium sulphate and sodium sulphate at three different concentrations (250, 500 and 1400 mg/L). The results demonstrated that the nanofiltration and reverse osmosis membranes achieved retention rates of sulphate ions ranging from 97.0% to 98.7% and 98.4% to 99.0%, respectively. The results also showed that the operating conditions had a significant effect on the retention of sulphate by reverse osmosis and nanofiltration membranes. With regard to the effect of the counter ion, it was observed that during nanofiltration, the retention rate of sulphate ions in the water to be treated was lower in the presence of calcium ions than that of sodium ions, whereas in reverse osmosis little influence of the counter ion was observed. Keywords: borehole water; drinking water; nanofiltration; reverse osmosis; sulphate ion removal; water treatment 1. Introduction Humans and water constitute an indestructible association. Water is ubiquitous in human daily life mainly for domestic (food, hygiene and sanitation), industrial and agri‐ cultural purposes. Globally, groundwater remains the main source of drinking water [1– 5]. Grönwall and Danert [6] reported that nearly 2.5 billion people in 2020 solely depended on groundwater to meet their drinking water needs. Generally, the quality and chemical composition of groundwater depend on the geological nature of the rock in contact with the water. For example, water flowing through sandy or granitic subsoils will be acidic and poorly mineralised, whereas water flowing through calcareous soils will be bicar‐ bonate, calcic and often have a high hardness [7,8]. Groundwater has long been consid‐ ered “clean water”, because in most cases it naturally meets potability standards and therefore does not generally require treatment. However, as groundwater quality varies from place to place [9], some may contain mineral elements in concentrations exceeding potability standards [10–13] and thus requires to be treated before consumption [7,8]. Citation: Sawadogo, B.; Konaté, Y.; Sossou, S.K.; Ado Saidou, N.F.A.; Nouhou Moussa, A.W.N.; Karambiri, H. Removal of Sulphate Ions from Borehole Water Using Nanofiltration and Reverse Osmosis. Water 2022, 14, 3422. https://doi.org/10.3390/w14213422 Academic Editor: Zhiliang Zhu Received: 19 September 2022 Accepted: 21 October 2022 Published: 27 October 2022 Publisher’s Note: MDPI stays neu‐ tral with regard to jurisdictional claims in published maps and institu‐ tional affiliations. Copyright: © 2022 by the authors. Li‐ censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con‐ ditions of the Creative Commons At‐ tribution (CC BY) license (https://cre‐ ativecommons.org/licenses/by/4.0/).