Sustainable Wastewater Management Through Decentralized Systems: Case Studies

There is a significant increase in the urban population in developing countries like India and consequently, this has thrown up a major challenge to Urban Local Bodies (ULBs) entrusted with the task of waste management. In India, less than 20% of the wastewater generated is getting treated. Recent studies indicate that the supply is roughly equal to the demand for the country, hiding wide regional variations with acute shortages in many parts. Since economic growth implies increased water use, the water situation can be expected to worsen rapidly. Even though water resources are not scarce from the perspective of total available water volumes, the precipitation is highly variable in time and space. In addition, the untreated or partially treated wastewater from human settlements is polluting the existing freshwater bodies, creating shortage of freshwater for different uses. Moreover, many studies have shown that centralized treatment plants are not a sustainable solution for countries like India, where the power supply is rarely continuous, and operation and maintenance are not secured. Hence, it will be advisable to treat the wastewater near to the point of generation and reuse it so that the environment is protected and reliable source of water supply is provided. Innovative decentralized wastewater treatment plants aiming not only at treating the wastewater but also providing other benefits such as the reuse of water, energy reuse or nutrient reuse-depending on the local context-are the need of the daywater treatment systems. Any sustainable wastewater management system should be oriented toward the 3R concept, i.e., reduce, recycle, and reuse. However, the selection of technologies/management strategies will be depending on the economic status of the society. An integrated wastewater management system is the base for a sustainable development in urban and peri-urban areas. It is important to quantify and characterize the amount of wastewater for (i) developing effective strategies to treat the wastewater, (ii) applying different technologies, i.e., anaerobic, followed by aerobic and physicochemical, and (iii) using the treated wastewater in a sustainable way taking into account the risks involved, e.g., using treated wastewater for toilet flushing, and landscaping. This chapter deals with the case studies of various sustainable decentralized/on-site wastewater treatment systems.