- City of Lakes
The city of Delhi is bestowed with 1011 water bodies (Environment Department) with each water body having an average area of between 0.5-2 acres and a depth of 1 m. The major sources of water losses from any water body can either be due to a) evaporation and b) percolation. Hence, filling a water body with the required volume to compensate the evaporation and percolation loss is required to maintain the water level in the water body.
As per data available from the Environment Department, 600 out of the total 1011 water bodies can be revived. Assuming an average 1-acre area for the 600 water bodies with 1 m depth, a total capacity of 540 MGD can be stored. During the first phase, 95 water bodies have been taken up by the I&FC Dept. for revival. A total of 180 crores have been allocated by the Dept for revival of water bodies.
Pilot projects undertaken on the revival of water bodies includes arranging for perennial sources of water for the waterbodies such as water sourced from decentralized STPs created near the waterbody or centralized STPs of DJB in addition to rainwater.
- Pilot Project to treat Ghoga Drain along with revival of Bawana Lake
- Area of implementation: Revival of water bodies, ground water recharge and decentralized wastewater treatment
- Pre and post implementation scenario:
- Location and source of water
Less than a mile away from the region`s garbage dump- Bawana landfill- the dry water body at Bawana is being revived with treated water from Ghoga Drain. This drain is located at village Ghoga with a total stretch of 6.18 km and a volume capacity of 145 MLD. Ghoga drain originates in village Ghoga and outfalls into Bawana Escape Drain near Pragati Power Station after traversing the villages of Ghoga and Sanoth. In addition to carrying raw sewage from neighboring villages, the drain also receives dairy waste from Ghoga dairy, waste water of WTP of DJB situated at Bawana- Narela road and storm water.
- Pollution in Ghoga drain and depleting groundwater levels
The BOD levels are in the range of 332 mg/L indicating presence of industrial waste. This untreated waste ultimately finds its way into Yamuna and is therefore critical to treat the waste in situ. In addition, unhygienic conditions (stench in the areas surrounding the drain in Ghoga village) were observed due to presence of untreated wastewater. CGWB reports observe that the groundwater levels deplete by 1.5-2 m every year and hence it is important to devise strategies to maintain and replenish groundwater levels.
Keeping in view the directions of NGT to improve the quality of water in drains, the Dept. of I&FC initiated plans to treat 1 MLD water using SWAB (Scientific Wetland with Active Biodigestor) technology. The water from Ghoga drain was proposed to be treated on the left bank of Bawana Escape Drain at RD 9900M before out falling into Bawana Escape Drain.
Salient features of the SWAB technology:
- Negligible operation and maintenance expenses
- Minimum electricity requirement
- Smaller footprint
- Facilitates recycle and reuse of water
- No foul odor and mosquito infestation
Post implementation scenario
The BOD levels decreased significantly from 330 mg/L to 32 mg/L after treatment by the wetland system. Work is on currently to procure electricity supply to operate the nutrient filters which will bring the BOD levels further down.
Plan for Ghoga lake revival
- Cost effectiveness of the innovation/technology:
The cost of setting up the natural STP, with a capacity to treat 1 million litres per day (MLD) of waste water, has been set up at a cost of ₹1.38 crore. The cost of treatment is ₹1.17/KL, while that treated using a regular STP will be around ₹5-7/KL making it a cost-effective STP.
- Replicability of the technology:
The SWAB technology is simple, cost-effective, sustainable and can be replicated as a treatment model for rejuvenation of dry water bodies. This treatment system using wetland plants is easy to replicate with factors such as source of water, topography of land and area available being critical while designing the system. A pilot scale to explore the feasibility of using SWAB system for wastewater treatment has already been studied at Rajokri Lake and has been recommended by the NGT Monitoring Committee to be a template for the revival of other water bodies. The Ghoga project is one of the first of natural sewage treatment plants (STPs) at a larger scale (1 MLD), which would treat sewage water chemical-free and then supply the treated water to revive the dry DSIIDC lake.