Capital needs to expand sewage treatment capacity, say Delhi Jal Board officials

Ten out of Delhi’s 37 sewage treatment plants (STPs) still require critical upgradation to meet design parameters, while 36 new decentralised sewage treatment plants (DSTPs) have been identified for future installation, as per the DJB document.

Large volumes of untreated wastewater continue to drain into the Yamuna. Delhi has 22 major drains that ultimately discharge water into the river. These include major ones such as the Najafgarh and Shahdara drains — which together account for nearly 80% of the pollution load entering the river within the city. As per the DJB, the Najafgarh drain alone discharges about 632 MGD with a Biological Oxygen Demand (BOD) of 96 mg/l, a key indicator of untreated sewage and nearly ten times higher than the permissible limit of 10 mg/l. In-situ treatment of drains or sub-drains is now being explored, said officials.

The document also stated that the DJB operates 37 STPs with a combined installed capacity of 814 MGD, of which 27 have been upgraded to meet the latest DPCC/CPCB norms. The latest plant to be augmented was Pappan Kalan Phase I that was upgraded in July.

However, the ten STPs which are not fully augmented are in different stages. Nilothi Phase I is expected to be completed by 31 December 2025. Upgrades for eight STPs — Ghitorni, Mehrauli, Okhla Phase V, Vasant Kunj Phases I and II, Keshopur Phase I, Yamuna Vihar Phase III and Molarband — are currently at the bidding stage. According to DJB officials, the work will be awarded this month and completed by December 2027. Another plant — Yamuna Vihar Phase I — is yet to even invite tenders, with DJB stating bids are only “likely to be invited” this month.

According to officials, sewage treatment is a “complex bacteriological process” that may show exceedances at times due to fluctuating sewage characteristics, industrial mixing, weather effects or equipment performance and ensuring compliance is critical.

In unauthorised colonies and rural belts, the DJB has identified 36 sites for decentralised STPs, totalling 171 MGD — many of which are now at the tendering stage with the completion targeted for December 2027. However, projects like the 3.5-MGD plant at Maidan Garhi remain stuck, with the land “yet to be identified by DDA”.

Apart from these, a planned augmentation of nine old STPs is expected to raise their collective capacity from 78.8 MGD to 140.7 MGD. An additional capacity of 110 MGD is proposed at major STP sites like Rohini, Rithala, Nilothi, Pappan Kalan and Keshopur — with target dates stretching to 31 March 2029. A new 20-MGD plant at Jagriti is also among these STPs.

Together, these expansions of decentralised plants, augmentation of old STP units and major additions at large STP complexes would amount to about 343 MGD of new capacity.