A composite is a blend of two or more materials with distinct chemical and physical characteristics and an identifiable interface. Composite materials provide several benefits over other metal compounds. These benefits include superior toughness, high specific stiffness, high specific strength, gas barrier properties, corrosion resistance, low density, and thermal insulation. The continuous phase; known as the matrix, and the scattered phase; known as reinforced materials, comprise composite materials. Numerous fields, including the biological sciences, medication delivery systems, and wastewater treatment, have found use for nanomaterials (NMs), particularly nanocomposites. Membrane separation technologies have been widely used in wastewater treatment. Owing to their mechanical strength, structural and chemical durability, polysulfone (PSF) membranes are the most often employed membranes in wastewater ultrafiltration. Membranes are constructed from hydrophobic polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or polypropylene (PP), utilizing a variety of processes such as phase inversion and electrospinning. Several studies have been carried out to improve the hydrophilic qualities of the membrane's polymeric surface; more recently, metal nanoparticles (NPs) have been introduced to the polymer matrix to minimize fouling potential and improve membrane performance. Recent advances in nanotechnology assist in outstripping techniques for the removal of pollutants by overcoming the constraints of conventional treatment technologies and providing low-cost treatment methods with high capacity. This chapter introduces the classification of membrane, NPs, and nanocomposites and their efficacy in removal of contaminants. The benefits, limitations, and new developments in water, wastewater, and groundwater treatments are also evaluated and scrutinized.