A nutrient recycling system – looking at urban sanitation differentlyMay 30, 2013
City Ecosystem services and their management
A city needs a vast hinterland to support its population base as well as its economic engine. From here will come the food, water and other resources to keep it going. Of these water is a crucial limiting factor in the sense it has to be physically managed in large volumes to be delivered to every household daily.
Managing the catchment of the rivers which are the primary source for water will need to figure high on the list of priorities if a city wants to be sustainable and just.Catchment management will ensure that the forests and the groundwaters are protected so that the rivers continue to flow with high quality and quantity of water. These are upstream interventions for a river.
Catchment management can also mean taking care and protecting the water bodies within the city . Lakes and groundwater need to be kept away from pollution and encroachment as well as recharged with rainwaters.
Downstream needs : On the other hand the city also needs large areas of land downstream in a certain sense to manage the vast streams of waste that flow from it. Solid waste generated need land-fills as disposal areas. Liquid waste flowing through streams need large areas too for absorption of the nutrients.
In a strange conundrum the valley of the Vrishbhavati river is one of the greenest areas around Bangalore while the surrounding areas suffer from drought and a shortage of water. The city generates waste-water in the millions and about 500 million litres per day should flow out in the Vrishabhavati valley. The Byramangala reservoir , spread over 420 acres of land , receives all this water. It is a surprisingly scenic spot and deceptively beautiful . Built in 1940 this reservoir continues to provide irrigation water through canals to many a farm field. The reservoir itself used to be a breeding ground for fish but all that has gone with the introduction of the African catfish into it.
The deceptively beautiful Byramangala lake receives about 50 % of the citys waste-water
Downstream the waste-waters undergo a remarkable transformation. The soil , the vegetation and farmers transform this nutrient rich water into a green bounty. Slowly and surely as the river progresses one sees an improvement in the quality of the waters and by the time it joins the Arkavathy it can hardly be recognized as a foul smelling black stream which leaves the city. The Ecosystem services provided by nature is truly remarkable.
Slowly but surely nature transforms black-water into better quality
This is not to say that there are no problems. Industrial effluents should not enter the stream at all . Domestic sewage too should be treated to a certain minimum standards before release to the river. Groundwater in around 50 % of the bore-wells was reported as contaminated especially with nitrates and bacteria according to a study. Farmers and field workers too have been reported to suffer from skin disease and other ailments.
How green is my nutrient laden valley ?
While source control and elimination of the problem there is the best way it is still true that these waters are now essential for the livelihoods of hundreds.
Can waste-water irrigation be integrated with the ecosystems approach of managing it?
Can the city think of identifying the entire area of the Byramangala reservoir and its command area as a zone which produces ecological benefits and for which the city should support the land and its cultivators ? Can this land be bought by the city and managed with the farmers and a palate of crops developed which will not enter the food chain of the residents of Bangalore? Can the villagers downstream be supported to access safe water and also be rid of the disease impact of using the waste-water? Can we think other than conventional waste-water treatment plants but say vast bio-diverse managed wetlands to clean the sewage that emanates from our city and for which each and every citizen is personally responsible? Can the institutions in our city rise up to the challenge and can the city become ecological and water wise ? If any city can be the first this city has a fair shot at it.