Mapping Unsafely Managed Sanitation Around the World

The Challenge

Lead Researchers: Prof. Barbara Evans (Professor of Public Health Engineering; Deputy Head of School of Civil Engineering), Prof. Andy Sleigh, and Dr Paul Hutchings
Key Partners: WHO, UNICEF, Bill & Melinda Gates Foundation, World Bank, Eawag/Sandec, GIZ, CSE India, WaterAid
Global Reach: Adopted in 100+ cities across Asia, Africa, and Latin America; over US$1.1 billion in urban sanitation investment informed

Under the Millennium Development Goals, sanitation progress was measured largely by one question: does a household have a toilet? That measure hid a much larger problem. In rapidly growing cities across Africa, Asia, and Latin America, most households use on-site systems such as pit latrines or septic tanks, or connect to sewers that discharge without treatment. Having a toilet at home does not prevent disease if the waste is then dumped into a neighbourhood drain, canal, or river.

Municipal engineers and city mayors knew the problem existed, but lacked a straightforward way to quantify where excreta went after leaving the household, or to explain the scale of the failure to finance ministries and development banks.

The Research

Research led by Prof. Barbara Evans (Professor of Public Health Engineering; Deputy Head of School of Civil Engineering) and Prof. Andy Sleigh at the University of Leeds examined the entire urban sanitation service chain, from containment at the household, through emptying and transport, to treatment and final disposal or reuse.

Working with international partners including the World Bank Water and Sanitation Program, GIZ, Eawag/Sandec, the Centre for Science and Environment (India), and WaterAid through the Shit Flow Diagram (SFD) Promotion Initiative, the Leeds team co-developed a standardised methodology and open-access graphic generator that traces excreta flows through a city. The resulting diagram shows, at a glance, the proportion of a city's faecal waste that is safely managed (green) versus the proportion that is discharged untreated into the urban environment (red), and pinpoints where along the service chain the system fails.

Alongside the SFD work, Prof. Evans served as senior technical adviser to the WHO/UNICEF Joint Monitoring Programme (JMP) Sanitation Working Group, providing the engineering and public health evidence base for how global sanitation targets should be defined and monitored after 2015.