Human civilisation is rightly considered to be a departure from the natural order. No other species on this planet manipulates its external environment to the extent that we do for our needs. Yet, it stands to reason that we thrive most when we work with the environment instead of against it. Nowhere is this more true than in the realm of sewage disposal. It may seem odd to suggest that our economic and environmental salvation lies in eco-friendly potty disposal. But as it happens, getting our sh*t together is more than a mere metaphor when it comes to avoiding both ecological collapse and facilitating basic sanitation for all.
The biggest living proof of how nature is our friend in matters of sewage treatment is found in the East Calcutta Wetlands. The East Calcutta Wetlands are a vast network of marshland that cover an area of 125 sq km lying to the East of the city of Calcutta, India. These wetlands were named and discovered by a man named Dhrubajyoti Ghosh, a humble sanitation engineer, who then went on to win an award from the UN due to his assiduous efforts to conserve the wetlands.
The wetlands are, by all means, a marvel, as explained by Ray Chaudhuri Et al, in an article in the OnLine Journal of Biological Sciences. The waterways and channels of the wetlands receive heaps of sewage and other solid waste (about one-third of the sewage produced by a city of over ten million) which are then deposited in setting ponds. In the shallow settling ponds, the waste is broken down by the sun's UV rays and the algae and plankton that are abound in the marshland. Water hyacinth processes some of the heavy metals in the purification process. The byproduct of this naturally-processed sewage is the nutrient-rich water and soil, which is used for extensive fish farming and vegetable farming. Precisely, the wetlands provide around 150 tons of vegetables daily and around 10,500 tons of fish every year. This is a great boon for Calcutta, its Bengali population is famously pescitarian and around much of the vegetable produce from the wetlands is supplied to the city. These activities also provide direct employment to more than 50 thousand people.
It is important to note that the wetlands are the result of years of assiduous human efforts, they aren't just nature's gift presented on a platter. Originally, the region consisted of large salt water lakes between the Bidyadhari river in the East and the Hooghly river in the West. The Bidyadhari river does not exist any longer due to the fact that the region became a dumping ground for the waste coming from the Second City of the Empire during the days of the British Raj and also post Indian Independence. Great strides were taken by a certain Bholanath Sen, who leased tracts of land in the marshes in 1879 and began growing vegetables using a unique landform which had alternate rows of garbage and water bodies. Thereafter, in the 1930's a gentleman named Bibhuti Bhushan Ghosh, innovated a perennial system of wastewater fisheries and in 1985 a comprehensive map of the marshes was published. Legal protections were put in place in 1992, when the High Court at Calcutta issued an order prohibiting the reclamation of the wetlands, which was followed by a law passed in 2006 that set up a conservation authority.
Thus, unlike the many stories of humanity being an enemy of the planet, the wetlands represent a concerted human attempt at preserving ecological balance. Not only that, the East Calcutta Wetlands are a beacon for humanity, guiding us to a future that might not involve climate collapse.
Man-made wetlands have now been recognised as a cheap and extremely effective means for dealing with effluents and waste generated by urbanisation. The first most striking feature of this organic sewage treatment mechanism is how little it costs. A book titled ‘Treatment Wetlands’ published as far back as 1996 estimated that to treat 3,786 cubic meters of sewage per day, a conventional sewage treatment plant would cost $4.12 million for construction and then require $156,000 as yearly maintenance costs. However, for treating the same amount, a constructed wetland would require only $3.6 million as construction costs and a mere $45,000 as yearly maintenance costs. Recently, a sewage treatment plant in Arizona was replaced by a constructed wetland which cost a minuscule $3.5 million, compared to the estimated $625 million that would have been spent on upgrading the said plant.
Of course, all of this comes with a catch, we need a lot more land to construct a wetland than a conventional sewage treatment plant. For treating 3,786 cubic metres a day in a wetland, as mentioned above, one would need 90 acres of land, whereas a treatment plant would occupy a mere five acres of land. This problem would be multiplied by the fact that much expenditure would have to be incurred by authorities to acquire such lands and compensate the owners. But there is an opportunity presented by this challenge.
The use of constructed wetlands for aquaculture and vegetable farming can bring about serious economic rewards to any region. Non-arable land of low value can be transformed into fertile areas that bring prosperity to local communities as in the case of the East Calcutta Wetlands, thus increasing the asset profile and revenue-generation capacity of the authorities acquiring such land. In turn, this can help such authorities raise finances far more easily for funding projects that are proper investments rather than mere sewage treatment facilities.
That apart, there is the conservation of biodiversity that follows as a direct consequence of constructing wetlands. It is estimated that the East Calcutta Wetlands harbour around 104 plant species, 40 bird species, 20 important types of mammals, many rare endangered reptiles, and more than 52 varieties of fish, of which 34 species are endangered. It is well-known that habitat destruction due to human activity poses perhaps the greatest threat to Earth's flora and fauna. A constructed wetland bucks this trend. It's usage and making involves human activity that brings about habitat conservation and enrichment, thereby contributing significantly to environmental conservation in general. By making constructed wetlands an essential feature of urbanisation, we can turn our cities into supporters of the environment instead of being a drain on the same.
Indeed, constructed wetlands can be sensitive to climatic conditions, unlike traditional sewage treatment plants. Floods, droughts, changes in soil salinity, cyclones, etc., can really affect the viability of a man-made wetland. However, even that drawback is a blessing in disguise. The wetland can act as the first line of defence against such weather events, absorbing the worst of the impact, leaving cities unharmed in many ways and circumstances.
Finally, wetlands can be a great source of commercial utility. They can be beautified to create marvelous recreational spaces. In fact, the Environmental Protection Agency gives excruciating details on the kind of plant species that can be added to beautify man-made swamps in a document that lays out a plan for constructing wetlands. The flora and fauna can generate tourism-related revenue. The lakes can be used for boating and other light water sports. In other words, our shit can literally be used to make life more fun.
Keeping all of that in mind, it seems almost bizarre that such an easy and brilliant solution for one of humanity's fundamental problems is not utilised more often. Sewage swamps and wetlands are meant for many more cities and towns than my home city of Calcutta. If constructed scientifically and strategically, they can truly assist in sustainable development whilst also alleviating poverty and saving communities that may have been damaged due to the denigration of soil quality and loss of livelihoods. It is hoped that this article will stir the public imagination and induce readers to bat for an ingenious solution to a perennial problem.
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