Improving global food security through cost-effective reuse of safe wastewater

Professor D. Mara  and Dr P. A. Sleigh, Faculty of Engineering

Leeds research into the effectiveness of wastewater treatment has enabled many countries to reduce costs and grow more food safely for local consumption and export.

The cost-effective reuse of wastewater for agriculture is essential for global food security and is becoming an increasingly urgent issue as many countries face severe water stress, but it poses serious health risks. Several countries are heavily reliant on wastewater for irrigation for growing food for domestic consumption and also for export to Europe.

…the University of Leeds has played an important role in developing new approaches to assess and manage the risk associated with wastewater reuse, and in helping to operationalise the 2006 WHO Guidelines…

Senior Irrigation Water Economist, World Bank, USA

Quantifying the risks from reused water

Leeds researchers established the effect of different irrigation techniques on pathogens and investigated the effectiveness of wastewater treatment processes in developing countries. They used the findings to link treatment processes and irrigation techniques to health risks. Further studies characterising health risks provided the basis for a Quantifiable Microbial Risk Assessment (QMRA) to assess the risk posed to health. Leeds simplified the application of QMRA and used it to show that the quality of wastewater which can safely be used for irrigation is significantly lower than previously thought.

World Health Organisation (WHO) guidelines were originally based on the assumption that water for irrigation should meet the same quality standards associated with drinking water. WHO worked with Leeds to develop wastewater standards based on acceptable levels of health risk for their 2006 guidelines. In 2010 the World Bank also adopted a risk-based policy approach and extended the scope of water reuse to crop irrigation, enabling many countries to reduce the costs of wastewater treatment and grow more food safely.

Putting policy into practice

The World Bank has commissioned country-level analyses to assess the potential benefits of wastewater re-use. Leeds used a QMRA-based methodology on the Nile Basin (where around 10 billion m3 of drainage water is used in agriculture annually) and identified waste management options that are six times more cost-effective than the current processes.

The adoption of the QMRA approach and risk-based regulation by WHO and the World Bank has led to its adoption around the world. Tunisia now treats most of its urban wastewater and plans to expand wastewater irrigation to 20,000–30,000 ha by 2020, whilst 50% of Israel’s irrigation water is provided from sewage.

Funder: Department for International Development