Suitability of Grey Water Recycling as decentralized alternative water supply option for Integrated Urban Water Management

The imbalance between water demand and supply has become a significant concern of human life as demand is increasing exponentially. With growing urbanization, this imbalance has become more acute in urban areas. So implementation of alternative water supply options has become an inevitable need for urban water management. Grey water and black water recycling is one of the most reliable options to reduce urban water demand. Both centralized and decentralized recycling systems are used based on available site, economic condition and treatment system facilities. But decentralized systems should be given priority for grey water recycling to reduce burden on centralized system and save transportation cost. This paper has proposed a strategy of recycling grey water separately from black water by using decentralized approach. There are various kinds of grey water treatment systems around the world. A review of those processes has been done to identify the best suited processes at household and community level. Septic tank, constructed wetland and intermittent sand filter are identified as the most suitable processes for decentralized treatment due to the simple operation and maintenance facilities as well as cost effectiveness of these systems. Some case studies have been presented to demonstrate the successful execution and impressive performance of these systems on cluster level. Though the systems contain some disadvantages, effective uses of these systems can be made with proper management, execution of awareness program and strict monitoring practices among users. I. BACKGROUND Sustainable development and human and ecosystem health is on threat because of continuous depletion and pollution of freshwater (Furumai 2008). With the increasing rate of population growth urban water demand is rising worldwide (Sharma & Vairavamoorthy 2009). Furthermore, the capital and operation and maintenance costs of treatment plants, allocation and transport cost are increasing which make the condition worst (Sharma & Vairavamoorthy 2009). With more than half of humanity urbanized, an integrated and holistic view to the water supply and demand needs to be obtained as early as possible. The key concern is to create a proper balance between water demand and supply with respect to the social, economic and environmental overheads (Fattahi & Fayyaz 2009). To overcome the increasing water demand, a very simple strategy is to follow the 3R options- Reduce, Reuse and Recycle. Sustainability of integrated urban water management system is largely dependent on how well these water supply options are put into operation. Rainwater harvesting, stormwater harvesting are the alternative water supply options for reusing water and wastewater like black water, grey water recycling are the options for recycling for urban water management. 1.1 Recycling system Demand management, using of rainwater and stormwater are climate dependent and non reliable sources. Where wastewater recycling is another resource which is reliable, reduce the water demand and decrease the amount of waste to be treated. Therefore, wastewater recycling or management is gradually getting importance in the low and middle income countries where public health and environment is on a stake because of inadequate wastewater management. Appropriate recycling system of wastewater reduces water cost as well as increase the food security and public health. 1.2 Decentralized treatment system Moving toward more sustainable urban water practices involves moving away from the incompetence