12 more STPs to treat sewage discharged from Najafgarh in Delhi

DJB plans 12 new sewage treatment plants to reduce untreated sewage in Yamuna, focusing on Najafgarh drain, with a completion target of December 2026.

The Delhi Jal Board (DJB) is working on developing 12 new sewage treatment plants in the Capital with the aim to reduce untreated sewage being dumped from the Najafgarh drain into the Yamuna river, officials said. The DJB has started work on a 49.5 mld (million litres per day) capacity wastewater treatment plant in southwest Delhi’s Chhawla along with 11 units of smaller de-centralised STPs (DSTPs) and pumping stations.

Najafgarh drain at Inderlok in New Delhi on April 29. (Sanchit Khanna/HT Photo)

A senior DJB official said the bids for the project have been invited. “Yamuna cannot be cleaned unless the Najafgarh drain is cleaned first. A series of DSTPs is to be developed to treat wastewater and Najafgarh basin is being prioritised. First set of bids for development of treatment plants for this basin have been invited and the project is likely to be awarded in the next one month. These projects will come with ten years of operation and maintenance clauses. We are treating this drain cleaning work under the Sahibi mission,” the official added. Notably, Najafgarh drain is also referred to as erstwhile Sahibi river.

DSTPs are facilities which are set up at the origin site of the wastewater.

The agency will be expected to take 15 months for the development, another one month for commissioning and two months for carrying out trial runs of the DSTPs, officials said. Besides a larger plant in Chhawla, other DSTPs will be located in Jaffarpur, Galibpur, Khera Dabar, Hasanpur, Kazipur, Shikarpur, Sarangpur, Kair, Kakrola, Kangaheri and Dichon Kalan.

A DJB official explained that the Najafgarh drain, which meets Yamuna near Wazirabad, is too large for it to be tapped. “It is almost a small river. The entire drain cannot be diverted or tapped therefore a series of smaller treatment plants will be added near the sewage generation points and colonies from where treated water will be released in the drain or it can also be used for other purposes,” the official added.

A DJB official said that as per the project conditions, these facilities will have a biochemical oxygen demand (BOD) and total suspended solids (TSS) of less than 10mg/L (milligrams per liter). “Currently, the BOD in these drains is estimated to be around 250-400mg/L and TSS levels are 300-500 unit,” official added.

BOD is the amount of oxygen required by the microorganisms to break down the organic material, while TSS is the dry weight of suspended particles present in water that have not been dissolved.

According to the parameters set by the Central Pollution Control Board (CPCB), STPs should have both BOD and TSS below 10mg/L post treatment. Ideally, the BOD levels should be zero and lower BOD levels indicate cleaner water.

For healthy aquatic life, the BOD in water should be below 5ppm (parts per million), a rise in which indicates increasing levels of pollution and negative impact on the aquatic ecosystems. A BOD of 1-2ppm is considered clean and unpolluted.

According to the Delhi Pollution Control Committee (DPCC) report for April, the Najafgarh drain contributes to 69.77% of wastewater in Yamuna in Delhi, followed by 16.12% by Shahdara drain, and 4.92% by Barapulla drain.

A DJB official said they are planning 40 DSTPs across Delhi, out of which 14 will be in the Najafgarh zone, and work on 11 has started. On April 16, the expenditure finance committee, headed by chief minister (CM) Rekha Gupta on Wednesday approved setting up of 27 DSTPs, treatment facilities and associated infrastructure at a cost of ₹3,140 crore. Currently, 37 centralised STPs are installed at a distant geographical location of the city and water is collected from different sources and treated for further use. “The treated water from DSTPs can be used locally to rejuvenate water bodies, horticulture use and other non-drinking purposes,” an official said.

“A deadline of December 2026 has been kept for development of all 40 plants. They will add capacity of around 92mgd (million gallons per day) water in Delhi,” the official added.