Washington, August 18 : Countries like India, China and Vietnam use wastewater for agriculture, which apart from its negative impacts, has its share of positive implications as well, and has recently received attention worldwide.
This has been indicated in a new 53-city survey conducted by the International Water Management Institute (IWMI) in Sri Lanka, which indicates that most of the developing countries studied (80 percent) are using untreated or partially treated wastewater for agriculture.
In over 70 percent of the cities studied, more than half of urban agricultural land is irrigated with wastewater that is either raw or diluted in streams.
The conclusions of the study are based on data gathered from a diverse sample of developing country cities, chosen on the basis of factors such as water scarcity and income levels.
According to IWMI researcher Liqa Raschid-Sally and lead author of a report on survey results, "Irrigating with wastewater isn't a rare practice limited to a few of the poorest countries."
"It's a widespread phenomenon, occurring on 20 million hectares across the developing world, especially in Asian countries, like China, India and Vietnam, but also around nearly every city of sub-Saharan Africa and in many Latin American cities as well," the researcher added.
Wastewater is most commonly used to produce vegetables and cereals (especially rice), according to this and other IWMI reports, raising concerns about health risks for consumers, particularly of vegetables that are consumed uncooked.
But at the same time, wastewater agriculture contributes importantly to urban food supplies and helps provide a livelihood for the urban poor, especially women, and recent migrants from the countryside.
According to Raschid-Sally, it isn't just affluent consumers of exotic vegetables whose welfare is at stake. Poor consumers of inexpensive street food also depend on urban agriculture.
Moreover, in Asia, rice-based farming systems, irrigated mainly with wastewater, figure importantly in urban food production, the researcher explained.
Across regions, poor women benefit most from farming within and around urban areas, according to survey results. They play especially prominent roles in certain cities of Africa, Central Asia and Latin America, accounting for more than 70 percent of urban farmers.
But, the report praises new guidelines established by the World Health Organization (WHO), which replace often unachievable water quality thresholds with more realistic health-based targets.
As a result, countries lacking the means to treat wastewater adequately can still reduce health risks through low-cost interventions, such as the use of drip irrigation and correct washing of fresh produce.
Current sanitation methods, though often inadequate, still offer entry points for introducing strategies to reduce health risks, according to the IWMI report.
The key aim of the IWMI research is to find feasible approaches whereby wastewater irrigation can continue strengthening food security and generating economic benefits, but without major health risks for urban consumers and farmers.