East Kolkata Wetland: A Multifunctional Niche of International Importance

Abstract

Problem statement: In the megacity Kolkata, the need for space to accomodate the ever increasing population is increasing day by day. As a result the encoarchment of the large wetland on the eastern frindge of the city is increasing and so is the threat of its loosing the status of Ramsar Status. Approach: Proper documentation of the existing traditional practice with sound scientific basis and the direct as well as indirect benefit that the city receives as a result of its existance could be an approach towards its conservation. Results: East Kolkata Wetland (EKW) is a unique example of a wetland ecosystem involved in both resource recovery and environmental protection and in the process providing a stable urban fringe to an expanding metropolis. It ensures economic benefit and employment generation because of resource recovery activities based on utilization of the city's sewage. It acts as a sink for city sewage and garbage, even at times a little flow of industrial effluents with toxic heavy metals as well as hazardous contaminants like sulphate and nitrate to name a few. The purification process operating there depends to a large extent on the activity of the diverse microbial population using liberal sunshine. On trying to understand the microbial flora, a rich diversity of the bacterial domain was revealed with immense potential for commercial application. The extracellular enzymes from microbial origin of EKW were used for detergent formulation, dehairing of hide at neutral pH, silver recovery from exposed X-ray films and so on. The microbes themselves could entrap metals inside them as nanoparticles, remove sulphate from solution and prevent nitrate mediated eutrophication. The soluble waste from the megacity goes through various rounds of purification in the waste water fisheries, called Bheri in local parlance before being used for agriculture. This in turn results in fish production and purification of the waste water up to 99% in terms of faecal coliform count and to a large extent for other parameters. The metal content in the muscles of the surface feeder and bottom feeder fishes were comparable to that of the same variety from rain water fed ponds, indicating safe use of the waste water. The agriculture using waste water mostly produces paddy and vegetables. The green leafy vegetables produced from EKW when compared with same variety from non-EKW were found to be healthy without any additional unwanted metal accumulation. The entire resource recovery process was relatively safe, ecofriendly as well as economical. Conclusion/Recommendations: Thus EKW purifies the waste of a large part of the city, generates edible resources, provides employment, houses diverse flora and fauna and also harbours a rich repertoire of microbes with immense potential for application. The objective of the present review is to emphasize the need of its conservation and also intensify the research on the microbial diversity in these wetlands.