"Globally the practice of wastewater treatment before discharge does not seems to be good at this moment of time. As per The United Nations World Water Development Report 2017, on average, globally, over 80% of all wastewater is discharged without treatment. The discharge of untreated or inadequately treated wastewater into the environment results in the pollution of surface water, soil and groundwater. As per WHO, water-related diseases kill around 2.2 million people globally each year, mostly children in developing countries. We need to understand that wastewater is not merely a water management issue - it affects the environment, all living beings, and can have direct impacts on economies. The establishment of UN Sustainable Development Goal 6 (Clean Water and Sanitation), ensure availability and sustainable management of water and sanitation for all, reflects the increased attention on water and wastewater treatment issues in the global political agenda. The author of this book is convinced that water reuse is one of the most efficient, cost effective & eco-friendly ways to ensure water resilience. The author also believe that embedding sustainability into wastewater treatment is the best opportunity for industries to drive smarter innovation and efficient wastewater treatment. In order to develop sustainable wastewater treatment, we need to evaluate wastewater treatment systems in a broad sense. Economic aspects, treatment performance, carbon emissions, recycling and social issues are important when evaluating sustainability of a wastewater treatment system and selecting an appropriate system for a given condition. The modern concept of industrial wastewater treatment is moving away from the conventional design. Wastewater treatment technology trend is moving towards extreme modular design using smart & sustainable technology".