Contamination of fresh and marine sediments and water environments by oil spills, urban runoffs, industrial and domestic effluents is demonstrating to be of critical concern as the presence of contaminants affects aquatic organisms and can quickly disperse to large as highlighted by the recent Gulf oil spill disaster. Polycyclic aromatic hydrocarbons (PAHs), Poly chlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and heavy metals like mercury, lead and manganese are among the ubiquitous trace contaminants of marine and freshwater systems. Presence of these contaminants raise concerns as small quantities of the organic chemicals have been displayed to be carcinogenic to mammals and can pose a prohibition to both human health and the aquatic biota. Innovative operations for treating wastewater containing heavy metals often include technologies for reduction of toxicity. Nanotechnology has rampaged plethora of scientific and technological fields; environmental safety is no exception. One of the most promising and well developed environmental applications of nanotechnology has been in water remediation and treatment where different nanomaterials can help purify water meanwhile different mechanisms including adsorption of heavy metals and other pollutants, removal and inactivation of pathogens and diversion of toxic materials into less toxic compounds. Today nanoparticles, nanomembrane and nanopowder used for revelation and removal of chemical and biological substances include metals (eg Cadmium, copper, lead, mercury, nickel, zinc), nutrients (eg Phosphate, ammonia, nitrate and nitrite), cyanide,  organics, algae (e.g. cyanobacterial toxins) viruses, bacteria, parasites and antibiotics.By tracing these technological advances to the physicochemical properties of nanomaterials, the present review outlines recent development in nanotechnology for wastewater treatment. The discussion covers candidate synthesis of magnetic nanomaterials (MNPs), properties and their mechanisms in water purification.