Water on earth is one of the most abundant natural resources, but only about 1% of that resource is available for human consumption. It is estimated that over 1.1 billion people lack supply of adequate drinking water, due to the rising cost of potable water, growing populations, and variety of climatic and environmental concerns. The physical processes such as filtration can remove the contaminants by transforming one phase to another but producing a highly concentrated sludge, which is toxic and difficult to dispose. In the above context, there is a real requirement for more efficient and powerful technologies for treatment of municipal and industrial waste waters. This can be achieved either by development of completely new methods or by improving the existing methods through some interventions. Nanotechnology is fast advancing and currently became more effective than the conventional technologies used in water treatment that offers safe opportunities for using unconventional water supply sources. In wastewater treatment application, a variety of efficient, eco-friendly and cost-effective nano-materials have been developed having unique functionalities for potential decontamination of industrial effluents, surface water, ground water and drinking water. Therefore, the problems related to water contamination and their remediation using nanotechnological approaches are considered in this book.