- As World Water Day drew attention to the increasing pressures on the world’s freshwater resources, IWMI sought to highlight the value of wastewater. Developed countries have long treated wastewater to make it safe for reuse, but this has not been an option for many poorer developing nations. In these countries, wastewater frequently pollutes waterways. With freshwater at a premium, many urban and peri-urban farmers now use wastewater to irrigate crops, some without knowing, others more deliberately. This can present a risk to human health from contamination.
Pay Drechsel, leader of IWMI’s research theme on Resource Recovery,
Water Quality and Health, was among the editors of the book
Wastewater: Economic Asset in an Urbanizing World, which aimed
to demonstrate that wastewater does not have to be an environmental
burden. The 14 chapters show that wastewater, being rich in nutrients
and a good potential source of energy, could be valuable for planners
seeking to make cities more sustainable. However, for that to happen
in the developing world, the processes involved need to be
financially sound. 
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The time is ripe to turn wastewater into an economic asset.
More than half of the world’s population already lives in
cities and this is set to rise further. Increasing demand for food,
feed, fiber and fuel is placing ever more pressure on limited freshwater supplies. Also, treating wastewater is cheaper than creating new reservoirs, and less energy-intensive and polluting than desalination or making long-distance transfers.
Wastewater can also play a role in closing the so-called rural-urban nutrient loop. Currently, nutrients primarily drawn from the soil in rural areas become stored in crops, which are mostly consumed in cities. In developing countries, the resulting human waste is often dumped in waterways, cesspits and septic tanks. Reclaiming carbon, nitrogen, potassium and phosphorus could enable cities to produce their own organic fertilizer, which could then be used to grow crops. This would particularly benefit the rapidly expanding urban and peri-urban agriculture sector.
IWMI’s dedicated Resource Recovery and Reuse (RRR) program is already exploring ways of profitably converting fecal sludge into pelletized fertilizer, for example, in Ghana and Sri Lanka. The hope is that this approach could be emulated across other parts of the developing world. “Wastewater is only waste if we look at it that way,” said Drechsel. “There are proven methods for transforming what we currently consider as waste into safe products that are environmentally and socially valuable. The final piece in the puzzle is finding ways to make these products economically valuable.”
