An analytical study on municipal wastewater to energy generation, current trends, and future prospects in South Asian developing countries (an update on Pakistan scenario)

The water scarcity and energy crises are major challenges, particularly for South Asian developing countries. Wastewater resource recovery always remained an untapped potential for South Asian countries, especially in Pakistan. Globally, municipal wastewater's global generation rate is about 331 km(3)/year; only a small proportion is treated and safely reused. Wastewater also has high energy content and can be greatly productive, whereas most of the wastewater treatment plants currently employed in developing regions are non-functional or taking high energy inputs. Many global level studies are being conducted for energy use reduction and the production of renewable energy from wastewater. In this review, installation of wastewater treatment plants is suggested in the context of economic and environmental feasibility for South Asian developing countries. Multiple factors showed the need for and high potential to installation of wastewater treatment plants for providing clean water under sustainable development goals and further to recover valuable contents from municipal wastewater. The tremendous need for infrastructure development became obvious to deliver clean water to communities that are using wastewater directly or indirectly for various purposes. Based on technical grounds, economic, social, and environmental challenges can be tackled with viable wastewater treatment plant design options in each country context. With each step of wastewater treatment, control strategies would minimize energy use and enhanced resource recovery will reduce pressure on the current natural resource base. Overall, the cost assessment, funding opportunities, research and development, and social acceptability remained the big factors to energy generation from municipal wastewater in South Asia.