Designing a Faecal Sludge Treatment Plant involves much more than selecting a treatment technology. Drawing on engineering work across 100, 200 and 500 KLD FSTPs for Haridwar Kumbh 2027, this guide explains how flow variability, tanker unloading, equalisation, biological treatment, hydraulics, pumps, blowers, sludge handling, layout and mechanical-electrical engineering come together to create a buildable plant.