Markandey Singh

1 Introduction Water is an essential but increasingly scarce resource, often called ‘blue gold’. Agriculture is the largest consumer of freshwater, accounting for approximately 70% of global withdrawals (Tariq and Mushtaq 2023). However, growing demands from population expansion, industrialization and urbanization, intensified by climate change, are putting immense pressure on freshwater supplies. At the same time, these activities generate large amounts of wastewater.