Urban growth has swallowed up and defiled lakes and rivers that were once their life-blood. This is because of
- Unplanned unscrupulous urban sprawls
- Focus on ‘assets’ while neglecting processes
- Leading to maximizing economic profits at the cost of social – ecological capitals
- Ignoring and disregarding quality of soil, streams, rivers, lakes and watersheds
- Multifold increase in waste generation per sq. km in urban areas (approximately 14 MLD per sq. km in Delhi while 0.1 MLD per sq. km while in Daula village - about 100 km from Delhi)
Centralization of sewage treatment facilities have several drawback that have led to a backlog of construction, ineffective and inefficient sewage collection, conveyance and treatment, and rapidly changing technologies leading to obsolescence of existing infrastructure. For the past 200 years, sewage management has been dependent on physicochemical methods, and more recently on biological processes. Ecologists H. T. Odum and Eugene Odum, suggested using natural processes for sewage management in 1930 and 40s, followed by William Mitch and Sven Jorgenson in latter half of the century. But even so, mechanical and infrastructural initiatives have dominated.
The principle of sewage treatment is separation of solids floating, suspended and dissolved –from water. Many physical methods (sedimentation, filtration, etc.) and biological (aerobic, anaerobic, etc.) methods are evolved over the period demanding more of energy and material inputs. This has pushed up treatment costs (considering 30 years project life) for conventional systems to about Rs.1 crore per million litres per year. Therefore, we need to go back to nature for waste management. Wastes are being processed naturally from billions of years since the life forms took birth on mother earth. This has culminated in multispecies intelligence of managing the wastes ecologically and economically.
Detritus food chain in nature has capacity to assimilate sewage constituents and transfers them into ecological cycles of nutrients. We need a paradigm shift in design concepts from calculable concentration models and performance criteria to ecosystem approach of using detritus induced complex food chain and nutrient cycles. Use of ecological processes in treating and assimilating nutrients from the sewage reduces capital as well as operational costs substantially. Conventional treatment systems reduce carbonaceous BOD only but remaining COD and non-carbonaceous BOD then lead to permanent undesirable changes in ecosystem of receiving water bodies. This can be avoided by using an ecosystem approach and ecological engineering to treat the sewage.