Kolkata Has World’s Largest Natural Sewage Treatment System, Thanks To One Man’s Lifelong Struggle

Sayantani Nath

West Bengal

Image Credits: East Kolkata Wetlands, Nagarik Mancha

From the narrow, dusty streets, as the traffic emerges into the wide roadways of E.M. Bypass, Kolkata, a waft of fresh air welcomes the commuters. The wide green fields, interspersed with tiny water bodies are a soothing relief for the eyes, sore with the sight of skyscrapers and pollution all around.

The East Kolkata wetlands, as this greener stretch of the city is called, actually has much more than what meets the eye. While crossing one of the many bridges over the lakes and canals, one might have wondered how the foul-smelling, dirty black water on one side ends up into pristine lakes on the other. The reason is fascinating, which has earned East Kolkata Wetlands the designation of a ‘Ramsar Site’. The wetlands constitute the world’s largest organic sewage management system.

Where does it all go?

While sewage treatment continues to be a serious concern for almost all the thriving metropolises of India, Kolkata, with its bustling population of 5.8 million is managing fine without a single sewage treatment plant. The amount of sewage water generated per day in the city is a whopping 750 million litres. So, naturally, the question comes, where does it all go?

The answer lies in the amazing ecosystem of the East Kolkata Wetlands – comprising diverse flora, fauna and microbes – which naturally filters the sewage water. More interestingly, the wetlands have been developed and maintained by humans – mostly the local fishermen and farmers, around 30,000 in number.

The discovery by Dhrubajyoti Ghosh

Residents were completely oblivious of the ecological wonderland lying in the heart of the city until 1981, when late Dhrubajyoti Ghosh, an erstwhile sanitation engineer, discovered it. He was appointed by the municipal authorities to check what happened to the city’s sewage water – a mystery till then.

In a 2016 interview with The Guardian, Ghosh referred to the natural sewage filtration system as ‘serendipity’. In fact, he was the one to name the region as East Calcutta Wetlands and later went to win a legal battle with the state government for preserving the site from real estate encroachment.

The miracle of East Kolkata Wetlands supports 30,000 lives

The wetlands represent an extensive network of streams and canals, connected with the distributaries of the Hooghly river – Kolkata’s historical lifeline. The wastewater released from the city’s houses is carried through these channels towards the marshlands.

Meanwhile, the UV rays of the sun and heavy microbial population breaks down the raw sewage waste, thereby refining the dirty sludge into nutrient-rich water. This water is further filtered by underwater and superficial algal growth in the lakes and ponds, rendering it highly favourable for the growth of freshwater fish. The algae serve as natural fish food, reducing the cost of pisciculture by almost half.

Apparently, fish thriving in sewage might not seem so appealing for the palette, but Dhrubajyoti Ghosh and a team of scientists have found them to be completely safe for consumption. One reason for this is the low level of harmful heavy metals in Kolkata sewage, thanks to the natural systemic breakdown of the sludge.

How the wetlands help combat inflation

At the same time, cultivation of vegetables and even paddy is practised alongside the banks of these canals and lakes. The nutrient-rich water negates the need for any chemical fertilisers or pesticides. Estimates show that Kolkata’s sewage water is treated naturally within only 20 days.

In the early hours of the morning, while the City of Joy is yet to wake up, a horde of small trucks and carriers can be found lined up alongside the streets of Salt Lake, Dum Dum and other localities surrounding the East Kolkata Wetlands. These vehicles supply fresh vegetables and fish produced in the wetlands to the markets of the city.

As a matter of fact, due to local farming in these marshes, vegetable prices are still incredibly low in the city, even when other major Indian cities battle skyrocketing inflation.

The vegetable cultivation and freshwater pisciculture at East Kolkata Wetlands have given rise to a community of farmers and fishermen dwelling in and earning their livelihood from the area.    

Ghosh won one of India’s first major legal battle for environment

It might be astonishing to note here that at one point, the city was almost on the verge of losing its most wonderful ecological wonder, to crony capitalism. As urban migration increased the population of the city, expansion in her outskirts was necessitated. Thus Salt Lake City was developed around the wetlands, following a well-planned protocol of organised urbanisation.

However, in the early 1990s, the West Bengal state government tabled plans to construct a world trade centre tower in the middle of the wetlands, which would have led to the encroachment of almost the whole area. Dhrubajyoti Ghosh resisted the idea, registering the help of an NGO.

Together, they started the movement PUBLIC (People United for Better Living in Calcutta) and filed a PIL to thwart the government’s project plans. The verdict ultimately went in their favour as Justice Umesh Chandra Banerjee of Calcutta High Court declared that the wetlands must be preserved to support the livelihood of the fishermen and farmers, as well as protect the environment.

Unparalleled dedication & legacy

In a bid to apprise the government of the environmental worth of the wetlands, Dhrubajyoti Ghosh had invited the then West Bengal Chief Minister Jyoti Basu to take a trip in the region with him. During the visit, Ghosh drank a glass of water directly from one of the ponds. To the utter disbelief of Basu, Ghosh did not suffer from any ailment as the water was as clean as it is claimed to be.

For his extraordinary work throughout his life, Ghosh was awarded the prestigious Global 500 Award by United Nations, adding him to the likes of notable environmentalists David Attenborough and Jane Goodall who were honoured with the same. His sole endeavour resulted in the recognition of East Kolkata Wetlands as a Ramsar site in 2002.

Ghosh, who passed away in February 2018, always lamented the unplanned urban expansion happening at present, as unscrupulous syndicates of real-estate developers are encroaching upon the wetlands. Despite his lifelong efforts, he failed to convince the government to set up a proper management system for East Kolkata wetlands.

Efforts For Good take

For decades, Kolkata citizens are unknowingly encouraging the principles of sustainability and recycling, as they continue to consume the produce from these wetlands. However, with Ghosh’s demise, an uncertain future lies ahead for Kolkata’s precious environmental miracle, unless the citizens proactively involve themselves in its preservation. Efforts For Good urges the citizens to take note of their natural blessing and work towards its conservation.

Also Read: 70-Yr-Old Kerala Writer Donates 10,000 Clay Water Pots To Save Birds In Summer; Planted 50,000 Fruit-Trees Last Year

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