WHO has published Kolkata's fishermen and farmers reuse what’s flushed down the toilet. Excerpt:
For more than a century, Kolkata’s underground sewer system has been pumping untreated wastewater into more than 250 ponds on 12 000 hectares of land in the East Kolkata Wetlands.
Through sunlight and oxygen, human sewage is converted into plankton and then consumed by fish that are grown and sold in the local market. The pond water is then channelled to irrigation ditches and used to grow vegetables, such as carrots, radishes and onions.
Kolkata’s wastewater reuse system, the largest in the world, recycles almost 90% of the city’s waste for aquaculture and agriculture. The fish and crops grown provide an income for more than 20 000 families who work in the area.
"Through reusing the wastewater, Kolkata's farmers and fishermen are not only helping reduce water and soil pollution, but also contribute to nutrition of the city's residents. But this practice has health risks – like diarrhoea or helminthic infections – on the farmers themselves and downstream communities," says Payden, sanitation engineer at WHO South-East Asia Regional Office.
"The challenge now is ensuring wastewater is treated and reused safely."
Safe wastewater reuse ever as important as fresh water supplies diminish
Worldwide, as water resources become scarce, urban centres expand and demand for food increases, wastewater reuse is becoming more attractive and viable. Today, it is estimated that more than 10% of the world’s population consumes food produced with wastewater and 40% live in water-stressed areas.
However, wastewater treatment is low in most developing countries, posing various risks to human health from diarrhoea, cholera, typhoid and worms. Untreated and poorly managed wastewater also helps spread antibiotic-resistant bacteria when it used for bathing, drinking-water or growing food.
"At any given time, nearly half the developing world’s population is affected by an illness or disease directly linked to unsafe water, inadequate sanitation or poor management of water resources," says Dr Henk Bekedam, WHO Representative to India.
In 2014, WHO estimated that moving from no sanitation to improved sanitation only reduces diarrhoea by 16%; however, when excreta is properly removed from households, treated and safely disposed, an additional 63% reduction in diarrhoea results.