Author – Shubha Lakshmi K
Joint efforts by citizens of Delhi and Delhi University have ecologically revived Neela Hauz, one of the biggest lakes of South Delhi using an economical and natural process named Constructed Wetland Systems. The revival of the lake attracts migratory birds and contributes to the ecological health of the Neela Hauz biodiversity park.
The lake once was a major source of freshwater in South Delhi, but growing urbanization has resulted in polluting the lake. By 2014, the lake was occupied by water hyacinths and other water weeds. Gradually, raw sewage seeped in and parts of the lake got encroached. Citizens became concerned about the issue and took it the Delhi high court.
The court ordered the Delhi Development Authority to restore the lake. The authority took help from Professor C R Babu and his team at the Centre for Environmental Management of Degraded Ecosystems in the University of Delhi to complete the task.
Professor C R Babu and his team worked on the idea of a Constructed Wetland System [CWS] for two years. The team came up with a solution of treating raw sewage water from a nearby village Kishangarh. They designed and built a CWS to treat sewage through Bioremediation and let it flow into the lake.
Constructed Wetland System treats waste water in a two-step process:
- Raw sewage is stored in vacant land for a day in order to enable oxidation and aerobic degradation.
- Water is stored in a pond where 20 types of aquatic plants cleanse the toxins in it.
The treated water from the pond flows through pebbles, ridges and gets filtered before entering the lake. Professor C R Babu says CWS is economical, efficient and reliable when compared to mechanical sewage treatment plants that cost crores of rupees and require regular maintenance. The beauty of CWS is that it requires zero electricity. The water flows by a natural gradient. The lake’s CWS has been in operation for more than a year. It has resulted in a 20 feet deep lake and treats a million litres of sewage per day.
Neela Hauz lake’s revival has set a great example for a CWS and natural ways of wastewater treatment. The success story has made officials to present the concept to Delhi Jal Board for implementation in other water bodies. They should consider CWS to treat sewage discharged into the Yamuna river, which could also create alternative sources of water.