Increasing urbanization and industrialization has led to a dramatic increase in demand for clean potable water. Nanotechnology is used in environmental applications to eliminate pollutants, pathogens, and other effluents from water. Nanomaterials have gained importance in sustainable development. Alumina (Al2O3) and its composites are generally used as nanomaterials because of high surface area, porous nature, large number of active sites, formation of meta-stable phase and hexagonal structure, which makes it a potential candidate for water treatment. The nano alumina can be coated on membranes and the composites can be used for purification of water, specifically for the removal of heavy metal ions, dyes and other microbes. The prime focus of the review paper is the treatment of water using alumina composites; the same can be extended to other applications like dye removal and desalination with some modifications.