Rajokri Lake Rejuvenation Project

Creation of new green areas, Management and improved protection of rivers and other blue areas, Ecological restoration of ecosystems, Transformation of previously derelict areas

The project had the following objectives: - Revival of the lake through a scientific wetland system with active biodigesters (SWAB) technique (1, 2, 4) - Improving water quality and reducing the pollutant levels to acceptable norms (1,2) - Landscaping of the area for public gatherings (5) - Designing space for social and religious activities (2) - Construction of green play areas, including open gyms, to improve recreational activities (5) - Promoting groundwater recharge (2) - Act as a buffer to store floodwater by acting as natural reservoirs to store excess water during rainfall and prevent flooding (2, 7).

The lake was revived using SWAB (scientific wetland system with active bio-digester) technology to clean the sewage discharged into it. This system was constructed using two main parts - (1) a sedimentation tank equipped with a biodigester and (2) a constructed wetland system (Ref 4). In the first part, about 60% of the treatment takes place by using the sedimentation process, after which the microbes act on the organic part of the accumulated sludge. In the second part, the partially treated water is moved into the artificially constructed wetland, which is lined with a gravel bed and planted with hormonally treated wetland plants (2). For implementation, first, the flow of domestic wastewater into the lake was stopped, and the accumulated sludge and solid waste were removed to increase the capacity of the water body and allow better groundwater percolation. Next, raw wastewater was channelled into a single large drain equipped with mesh filters to remove large pieces of waste. The waste flowing through this drain was then channelled into the biodigester, followed by the gravel bed of constructed wetlands containing specialized plants (Ref 2). The sewage water from the nearby neighbourhoods is treated using a sedimentation-biodigester tank and gravel bed with bioremediation-capable plants (Ref 2). A wetland ecosystem was created using plants capable of reducing heavy metals and other organic materials. Gravel beds in terrace-like steps help increase the retention time of the treated sewage water allowing further purification. To protect water released into the lake from algal bloom and reduce pollutants, treated plants were used, which have higher nutrient uptake capacity and absorb pollutants (Ref 2,3). The project implementation was split into two major parts (1) construction of the wetland system and (2) landscape, civil, electrical and horticulture work (Ref 5 ). This included the construction of an "amphitheatre that doubles up as Chhath Ghat (an ancient Hindu Vedic festival historically native to the Indian subcontinent) for public gatherings; green play areas with open gym and swings; gravel based walking pathways that also double up as rainwater harvesting channels;" (Ref 5). Landscaping at Rajokri has been designed in such a way as to prevent flooding. Rain gardens on two ends of the lake ensure that water drains into the lake. Now that it has been revived, Rajokri Lake can play an important role in inhibiting flooding in the Delhi region" (Ref. 2), and improving water availability for the local's needs (Ref. 3).

• Local government/Municipality
• Citizens or community groups