Global use of wastewater to irrigate agriculture at least 50 percent greater than thought.
The use of untreated wastewater from cities to irrigate crops downstream is 50 percent more widespread than previously thought, according to a new study published this week in the journal Environmental Research Letters.
Such situations account for the majority of agricultural water reuse worldwide, but have been difficult to quantify on a global level due to different views of what constitutes diluted wastewater versus polluted water.
This includes improved wastewater treatment, but also preventive steps on farms and in food handling, since capacity for water treatment is increasing only slowly in developing countries.
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Of the total area of 35.9 million hectares, 29.3 million hectares are in countries with very limited wastewater treatment, exposing 885 million urban consumers as well as farmers and food vendors to serious health risks.
"While actions aimed at protecting human health are the first priority, we can also limit the hazards through a variety of tested approaches aimed at safely recovering and reusing valuable resources from wastewater.
These include the water itself but also energy, organic matter and nutrients, all of which agriculture needs.
Safe resource recovery and reuse have significant potential to address the health and environmental risks, while at the same time making cities more resilient and agriculture more sustainable, contributing to more circular economies."
More information: A L Thebo et al, A global, spatially-explicit assessment of irrigated croplands influenced by urban wastewater flows, Environmental Research Letters (2017).