How does dirty sewage become clean water? In this special Techpana video, we take you inside the Guheshwori Wastewater Treatment Plant to see how sewage from Kathmandu is collected, filtered and biologically treated before the processed water is released into the Bagmati River. From removing plastics and solid waste to sedimentation, aeration, clarification and final disinfection, we explore the technology behind the entire wastewater treatment process. We also look at how the plant handles sludge, produces biogas and generates electricity from the treatment process. The plant currently has the capacity to treat around 32.4 million litres of wastewater every day, offering an important technological solution for keeping the Bagmati River cleaner.