As world water demand continues to grow there is a critical need to develop sustainable water treatment solutions. This chapter describes the potential for nanomaterials to improve the sustainability of water treatment. Nanomaterial-driven advances in disinfection, oxidation, membrane separation and groundwater remediation are discussed with a view towards their potential to improve existing technologies. Disinfection technologies include oligodynamic processes with silver nanoparticles to effectively inactivate microorganisms without disinfection byproducts being formed. Oxidation technologies include metal oxide semiconductors and fullerene-based sensitisers acting as light-driven catalysts. Membrane separation processes include the embedding of materials such as zeolites, carbon nanotubes and metal oxides to improve selectivity and reduce fouling. Remediation technologies include iron particles designed to target and transform waste compounds in situ. These and other emerging water treatment technologies must be assessed with life-cycle analysis to determine the full materials and embodied energy costs of acquiring raw materials, manufacturing, use and end of life for the materials contained within each process. These costs must be weighed against the potential benefits for water treatment to determine their sustainability.