Despite substantial Government investment and an expanding sewage infrastructure, the Yamuna remains one of India’s most polluted rivers. A new analysis ‘Titled Yamuna: The Agenda for Cleaning the River’, released by the Centre for Science and Environment (CSE), highlights the paradox at the heart of Delhi’s river-cleaning efforts.

Between 2017 and 2022, the Delhi government spent more than `6,856 crore to clean the Yamuna. The city now boasts 37 sewage treatment plants (STPs), claiming the capacity to handle 84 per cent of its wastewater, with nearly 80 per cent of households connected to the sewer network. Yet, the 22-kilometre stretch of the Yamuna that runs through Delhi remains biologically dead.

The report said officials must ensure that tankers collecting faecal sludge from areas without sewer connections do not dump it into drains or the river.

The 22-kilometre stretch of the Yamuna between Wazirabad and Okhla in Delhi, less than 2 per cent of the river’s total length, accounts for 80 per cent of its pollution load. The main reasons for the pollution are untreated wastewater from unauthorised colonies and slum clusters and the poor quality of treated water from STPs and common effluent treatment plants (CETPs).

Delhi, with its 37 sewage treatment plants (STPs) of 3,033 MLD, has the capacity to treat over 84 per cent of the generated sewage, estimated at 3,600 MLD. Of the installed capacity, some 2,574 MLD is being utilized — roughly 85 per cent. In other words, over 70 per cent of the generated wastewater is now being treated, which is a marked improvement over the last decade.

According to the Delhi Pollution Control Committee (DPCC), the 37 STPs in Delhi have a total capacity of 3,474 MLD, about 96 per cent of the sewage generated.

However, these plants are currently operating at only 80 per cent of their capacity, treating just 2,777 MLD. The remaining sewage flows untreated into the Yamuna. Of the treated water, only around 1,960 MLD meets the required quality standards, that is, the biological oxygen demand (BOD) and total suspended solids (TSS) levels should be below 10 milligrams per litre.

The report called for a fresh plan for the Najafgarh and Shahdara drains, which together contribute 84 per cent of the river’s pollution load in Delhi.

The report notes that Delhi does not have accurate figures on how much wastewater it generates, largely due to outdated population data and the informal use of water through borewells and private tankers. Without this information, it’s difficult to design a system that matches actual waste output. Large areas of Delhi are not connected to sewers and rely on desludging tankers to remove faecal waste. However, these tankers often dump untreated sludge into drains or directly into the river. There is currently no comprehensive regulation or tracking mechanism to ensure that sludge is transported to treatment plants.

According to the 2019 report of the River Rejuvenation Committee, out of the 900 MLD that was planned to be intercepted, roughly half had been completed by 2019 — 400 MLD. By 2024, it was claimed that 800 MLD is now being intercepted, but it is not clear how much of this is from the six packages for the key drains. This is also when pollution load has continued to increase in both Najafgarh and Shahdara, which clearly suggests that there is an urgent need to review and rework the plan.

CSE director general Sunita Narain said all such tankers should be fitted with GPS trackers to make sure the sludge is taken to sewage treatment plants (STPs) for proper treatment and reuse. She added that untreated water from unsewered areas should be treated near the river before being released.

Narain also said that one of the biggest problems in cleaning the Yamuna is the lack of clear data on the city’s population, which makes it difficult to know if the current treatment capacity is sufficient.Narain said the Delhi Government spent more than `6,856 crore on Yamuna-cleaning projects between 2017 and 2022.Despite this, the river remains polluted and dirty. Cleaning the Yamuna will take more than just money. It needs a new and improved plan, she said.

For areas not connected to the sewer system, Narain said the government does not need to invest in expensive pipelines, as managing faecal sludge through tankers is quicker and more affordable.She also said that STP standards should be set with water reuse in mind, as large investments needed to upgrade the plants to meet the stricter discharge standards delays the cleaning work.