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BY JULIO P. YAP JR.
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Friday, March 31, 2017
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FOR most people, they don’t think about what will happen to their excreta when they flush the toilet or pour water down the latrine.
However, for fisherman and farmers in Kolkata, India, excreta provides a natural fertilizer for their crops, food for their fish and an income to provide for their families.
For more than a century, the World Health Organization (WHO) said that Kolkata’s underground sewer system has been pumping untreated wastewater into more than 250 ponds on some 12,000 hectares of land in the East Kolkata Wetlands.
It was learned that 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 channeled to irrigation ditches and used to grow vegetables, such as carrots, radish, and onion.
Kolkata’s wastewater reuse system, the largest in the world, recycles almost 90 percent 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 diarrhea or helminthic infections – on the farmers themselves and downstream communities,” says Payden, sanitation engineer at the WHO South-East Asia Regional Office.
The challenge now is ensuring wastewater is treated and reused safely.
Worldwide, as water resources become scarce, urban centers expand and demand for food increases, wastewater reuse is becoming more attractive and viable. WHO said that today, it is estimated that more than 10 percent of the world’s population consumes food produced with wastewater and 40 percent live in water-stressed areas.
However, wastewater treatment is low in most developing countries, posing various risks to human health from diarrhea, 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.
In 2014, WHO estimated that moving from no sanitation to improved sanitation only reduces diarrhea by 16 percent; however, when excreta is properly removed from households, treated and safely disposed, an additional 63 percent reduction in diarrhea results.
To help countries safely treat, manage and reuse wastewater, WHO developed the Sanitation Safety Planning (SSP), a risk management tool in 2016.
The tool helps sanitation operators to apply WHO’s Guidelines for safe use of wastewater, excreta and greywater in agriculture and aquaculture and identify and manage the health risks along the sanitation chain.
The multi-barrier approach used means risk can be reduced through simple measure even when expensive treatment is not feasible in the short term.
WHO is now conducting a risk-assessment of the East Kolkata Wetlands utilizing the guidelines and SSP tool to help the city understand how to improve the system and reduce health risks to both fishermen and farmers who live in the area, as well as the wider community consuming the fish and vegetables produced. (jaypeeyap@ymail.com/PN)
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