Turning urban waste water to wealth

Poverty is often synonymous with a poor water supply, a lack of sanitation services, environmental degradation and poor health. Improving the water supply raises the issue of how to deal with waste water, 70% of which is channelled back into systems largely untreated. In many places untreated waste water is discharged into the nearest stream. Cities in the developing world have few resources to invest in waste water management. The results can be seen in waterways such as the Musi River in Hyderabad, India, the tributaries of the Red River in Hanoi, Vietnam, and irrigation canals in Pakistan and Central Asia, which are virtual open sewers.
By Liqa Raschid-Sally, Senior Researcher at the International Water Management Institute

Many poor farmers depend on waste water for their livelihoods, it often being the only water available. Occasionally farmers actually prefer such water for irrigation, as the nutrients it contains allow them to save on fertiliser. In Haroonabad, Pakistan, farmers on an irrigation-canal system sold their fresh water rights, bought waste water from the municipality and channelled it through the existing irrigation system to their plots. They saved fresh water and were more productive than farmers using conventional irrigation (gross profit margins of $840 per hectare compared with $614 per hectare). This was largely due to the year-round availability of waste water, which allowed for multiple growing seasons, as well as the additional nutrients it contained. In Ghana, farmers in urban and peri-urban areas use polluted water to irrigate vegetable plots and earn annual incomes ranging from $600 to $5,000 per hectare, lifting them above the poverty line. In India, along the banks of the Musi River, waste water is considered “black gold” to the 51,000 direct and indirect users who depend on it for their livelihoods.

However, there is a downside to this practice. The use of waste water for irrigation poses a threat to human health and the environment. The major threat to farmers and their families is from intestinal parasites – most often worms. It may also contain highly poisonous chemical toxins from industrial sources, including heavy metals, active hormones and antibiotics. The risks associated with these substances may, in the long run, pose a greater threat to public health than the risks associated with excreted pathogens1. However, from the farmers’ perspective, earnings from agriculture provide access to health care, nutrition and education. In the absence of any alternative, they are willing to live with the risk. But do they really have a choice?

There is a further dimension to the issue. The long-term use of waste water may also damage the soil under some conditions leading to soil clogging and salinisation, with eventual loss of productivity and damage to crops.

The environment may also be a source of solutions, however. Down the Musi River, water quality has improved because runoff from irrigated fields is cleaner than the waste water initially used to irrigate. The land can assimilate more waste than streams and ponds and, if designed properly, the system can be made sustainable at a lower cost. This is a clear improvement on the current disposal practice of dumping untreated waste water directly into streams.

These experiences suggest that we need to explore land use as a potential “sink” for waste water. A balance must be struck between the economic survival of families, and potential health risks to farmers and consumers and environmental degradation. This will require working in collaboration with policy makers, health experts, engineers and land-use planners.

1. Scott, CA; Faruqui, N. I. ; Raschid-Sally, L 2004. “Wastewater use in irrigated agriculture: Management challenges in developing countries” in Scott CA. Faruqui NI. Raschid- Sally L. (eds.) Wastewater Use in Irrigated Agriculture: Confronting the Livelihood and Environmental Realities, Commonwealth Agricultural Bureau International, Orient- Longman, and International Development Research Centre, Ottawa, Canada.

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