Scientific wetland with activated biodigestion (SWAB) of influent at Rajokri Pond

Last visited: December 2018 by Chhavi Sharda and Ruhil Iyer

Location: Rajokri, New Delhi
Scale: Neighborhood
Implementing organisation: Irrigation & Flood control department and Delhi Jal Board

Designed Capacity: 600 KLD
Area : 3000 sqm
Operational since : 2018
Capital cost : 77.15 lakhs
O&M: 10,000 – 20,000 per annum

Rajokri is an urban village located in the periphery of south-west Delhi. It is not connected to the city-level sewer network and untreated sewage or effluent from on-site sanitation systems (if any) find its way in a nearby water body. This water body is a lake located in the heart of the settlement. All the wastewater and storm water gets collected into this lake naturally as this is a low lying area. The natural catchment of Rajokrilake is largely sewage from the adjacent residential as there is no wastewater treatment facility.In order to improve the quality of water and lake conditions, Delhi Govt. envisioned to revive the lake and its surrounding. To do so a wastewater treatment system was installed for the incoming stream such that only the treated water enters the water body. The treatment technology at Rajokri is a nature-based system called as Scientific Wetland and Activated Bio-digester (SWAB). This is a type of constructed wetland system.

The wastewater from the residential colony enters through a lined drain which after screening is diverted into an underground sedimentation tank equipped with a biodigester. This is where biodegradation of solids takes place and solid free effluent is pumped into the wetland system by solar pumps into the inlet chamber. The wastewater from this chamber enters the artificial wetland. The wetland basin is gravel lined and is of 2.5m in depth consisting of baffle walls that directs the flow of wastewater through the basin. The plantation over the planted basin is based on the specific plants, such as umbrella palm and Cannas pp., normally found in natural wetlands with filtration and treatment capability. These plants are harmonically treated before being planted. The wetland basin is designed in the form of three steps that also ensures gravity flow and maximum retention time of wastewater to be treated. The treated water then enters the lake. Setting-up sand filter and activated carbon filters at the site is planned and yet to happen that will take energy through the solar panel that are already in place. The treated water will then be let out into the pond post treatment.


Artificial constructed wetland	Treated water in the lake and floating wetlands to maintain the quality

Water quality at inlet is BOD 150mg/L and TDS 2,215 mg/L which gets reduced to less than BOD 20mg/L and TDS 50mg/L. The pond water looks clean and there is no odour. The pond water is also used to maintain the developed landscape in the vicinity through water sprinklers.

To determine consistency in performance the inlet and outlet parameters require consistent monitoring especially with respect to seasonal change before it stabilizes. A maintenance contract was awarded along with the implementation according to which five years post implementation is included.