New Delhi: More than 23,000 industries operating across 17 industrial areas in Delhi are covered by 13 common effluent treatment plants (CETPs). While two CETPs in Narela and Bawana were upgraded in 2024, the remaining 11 are operating close to their assumed lifespan of 20 years. The Confederation of Delhi Industries and CETP Societies has flagged concerns about ageing civil infrastructure, worn-out mechanical and electrical equipment, outdated treatment schemes, and underutilisation.
What is a CETP?
A CETP is a centralised facility designed to treat effluents released from multiple industrial units. The treated water must meet the prescribed standards of the Delhi Pollution Control Committee (DPCC) for parameters such as pH, biological oxygen demand (BOD), chemical oxygen demand (COD), and ammoniacal nitrogen. However, the confederation claims most CETPs are unable to meet these water quality standards. Wastewater entering CETPs now contains a higher proportion of domestic sewage, and conveyance systems have not been desilted for years.
Government Response
Delhi environment minister Manjinder Singh Sirsa stated that the National Environmental Engineering Research Institute (NEERI) is conducting a survey to understand the upgradation requirements of the 11 older CETPs. “It will start submitting reports from next month, after which we will take action accordingly,” he said. An official added that the survey will focus on what is reaching the CETPs and what is being treated, considering the industrial area and other factors. “Once the survey is conducted, we can plan the upgradation,” he said.
Technological Upgradation Needed
In a recent letter to chief minister Rekha Gupta, the confederation highlighted the need for technological upgradation of the 11 CETPs, which were set up between 2001 and 2010. The total cumulative capacity of these CETPs is 212 million litres per day (MLD), but the inflow is only about 80 MLD—roughly 38% of design capacity—indicating overdesign relative to low available flow. The letter stated, “The prescribed effluent standards have become stricter, and the influent characteristics have shifted towards a mix dominated by domestic sewage alongside industrial wastewater, which was not the original design basis. Accordingly, technological upgradation is necessary to reliably meet current discharge norms, accommodate changed wastewater characteristics, and ensure long-term operational sustainability.”
Challenges Highlighted by Experts
Anil Gupta, board member of the Central Pollution Control Board (CPCB) and DPCC, and chairman of the Jhilmil CETP Society, pointed out that illegal inflow of domestic sewage from JJ clusters and nearby residential areas, along with changes in land use from industrial units to banquets, restaurants, and service stations, have altered influent characteristics. “It has increased BOD loads beyond design parameters, creating operational difficulties. Heterogeneous industrial wastewater poses uniform treatment challenges. Besides, DPCC’s pollution norms are more stringent than pan-India standards. Even NEERI-upgraded facilities at Bawana and Narela fail to consistently meet them despite advanced technologies,” he said.
S K Tandon, general secretary of the confederation, stressed that the CETP drainage system urgently requires desilting to increase inflow. “The system hasn’t been desilted or maintained for years. Consequently, septic, anaerobic conditions have prevailed in the closed conveyance system,” he said.
Expert Views on Urgency
According to experts, upgradation of CETPs is crucial. Bhim Singh Rawat, associate coordinator of the South Asia Network on Dams, Rivers and People, said the timeline for upgradation is being delayed. “Most CETPs are unable to treat heavy metals released from some industries. For instance, illegal dyeing units are present across the city, which are not connected to CETPs and end up releasing harmful effluents into drains that meet the Yamuna. Such polluting industries should be shifted. Besides, the policy of zero liquid discharge was introduced in 2019 to treat and recycle water, but it has not been implemented yet,” he said.
