Technological trends in manganese removal from groundwater: A review

Groundwater represents a valuable resource in Morocco and worldwide, in which manganese (Mn (II)) constitutes an important oligo element. However, its overabundance in drinking water may cause severe environmental and human health issues: neurotoxicity, Parkinson disease, emotional instability, hallucinations and even some aesthetic and operational problems. Efficient manganese removal is therefore mandatory in today's water treatment plants. Nevertheless, despite its importance, Mn (II) removal data throughout the different stages of groundwater treatment plants is still not well collected and specifically documented on regional and global scales compared to wastewater. Therefore, the present review provides an updated analytical state-of-art of Mn (II) removal from groundwater around the world, using current chemical and biological processes (e.g.: coagulation/flocculation, electrocoagulation, chemical and biological oxidation, filtration, membranes, adsorption, ion exchange resins, etc.). Processes mechanisms, operating parameters, and removal efficiencies of Mn (II), including MnOx recovery and reuse, are compared and thoroughly discussed. Finally, this review provides valuable knowledge and precious insights on Mn (II) removal technologies in water treatment plants, to protect human health from groundwater pollution and preserve our planet. •Microfiltration with a new immersed membrane seems to be promising to mitigate manganese from groundwater.•Biological and chemical autocatalytic oxidation provide high manganese removal efficiency.•The potential impact of MnOX generated in situ by chemical oxidation on manganese and other pollutants degradation is very noticeable.•Manganese dioxide nanoparticles are used as an adsorbent and allows an effective groundwater treatment in the presence of the external magnetic field.