Why Delhi’s Yamuna remains filthy despite ₹7,000 crore spent on cleanup

As Chhath wraps up, the Yamuna’s pollution woes resurface, fuelling fresh political controversy.

Despite more than ₹6,800 crore spent between 2017 and 2022, the river continues to remain among the most polluted in India.

In this conversation with The Federal, the Centre for Science and Environment’s (CSE) Sushmita Sengupta explains why Delhi’s efforts have failed, where the real sources of contamination lie, and what can actually make a difference.

Your report says over ₹6,800 crore has been spent on cleaning the Yamuna between 2017 and 2022, but the river remains filthy. Why hasn’t this money translated into cleaner water?

The Yamuna flows through Delhi for only 2 per cent of its total length, yet contributes to nearly 80 per cent of the river’s pollution load. Despite spending almost ₹7,000 crore, not much has changed. Most of this money has gone into infrastructure—building sewage treatment plants (STPs)—rather than addressing fundamental issues.

Delhi has 37 STPs, but we still don’t know how much wastewater the city produces. The last population census was in 2011, and since then, no updated census has been conducted. So when government agencies give population or wastewater estimates, they rely on projections rather than real data.

The Delhi Pollution Control Committee (DPCC) recently told the National Green Tribunal (NGT) that there’s only an 11% shortfall in sewage treatment capacity. But what we see on the ground tells a very different story. We don’t know the exact quantity of wastewater being generated, and that’s a big part of the problem.

Also read: Ahead of Chhath, AAP and BJP spar over pollution in Yamuna

Another major issue is that a large portion of Delhi’s population lives in non-sewered areas—unauthorised colonies and slums. These areas aren’t connected to sewage networks, and their waste often ends up directly in drains that flow into the Yamuna.

Also, Delhi relies heavily on groundwater. When 100 litres of water are used, roughly 80 litres become wastewater. But we don’t have accurate data on how much groundwater is being extracted. So the government’s estimates—based only on the amount of water it supplies—are incomplete and misleading.

If Delhi’s STPs can treat around 84 per cent of the city’s sewage, why is the Yamuna still so polluted?

That figure comes from the Delhi government’s own data. The DPCC submits monthly progress reports to the Green Court, and the August report says 37 STPs are almost operational, with just an 11% shortfall. But even then, the Yamuna remains dirty.

The problem is that these numbers are based on projected wastewater generation, not actual figures. The government’s calculations assume a certain population and water supply, but they don’t include the vast groundwater extraction happening across Delhi.

Because unauthorized colonies and slums aren’t part of the sewage network, their wastewater doesn’t reach the STPs—it flows into natural drains instead. So even if STPs are built, they can’t treat wastewater that never reaches them. The result is that untreated sewage continues to enter the Yamuna.

Despite the investments, drains like Najafgarh and Shahdara remain among the biggest sources of pollution. Why haven’t efforts to fix these worked?

According to the DPCC’s latest report, Delhi has 22 natural drains, and authorities claim to have tapped nearly all of them—except eight smaller ones. Yet, the Najafgarh and Shahdara drains remain major polluters.

Also read: Ahead of Chhath, AAP and BJP spar over pollution in Yamuna

Najafgarh alone contributes nearly 70% of the biochemical oxygen demand (BOD) load to the Yamuna. Authorities say these big drains can’t be tapped directly, so they focus on sub-drains instead. But until we address what’s entering these major drains, we won’t see real improvement.

Much of the problem again links back to non-sewered areas. Since these localities aren’t connected to the sewage network, their waste is dumped into nearby drains. Without tracking how sewage and sludge are disposed of, we can’t fix the problem at the source.

The Yamuna has almost no natural flow for nine months a year, with all water diverted to Wazirabad. How does that worsen the pollution crisis?

When the Yamuna enters Wazirabad, every drop of its water is taken away for supply. In return, what flows downstream is mostly sewage. For most of the year, it’s not a river—it’s a drain.

Because large parts of Delhi are unconnected to the sewage network, untreated waste keeps entering the river system. Take Sangam Vihar, one of India’s largest unauthorized colonies. It relies entirely on groundwater and uses septic tanks or holding tanks connected to toilets. If the sludge from these tanks isn’t properly transported to treatment plants—and much of it isn’t—it ends up dumped in drains or on riverbanks.

Our study found that only 136 vacuum trucks are registered with the Delhi Jal Board to safely transport sludge. But many unregistered trucks operate without oversight, disposing waste illegally. If we could track these vehicles using GPS and ensure all sludge reaches treatment facilities, we could solve a large part of the problem.

Your report says the Yamuna can be cleaned. What exactly needs to change?

First, non-sewered areas must be brought into the sanitation network. Every sludge transport vehicle should be fitted with GPS so authorities can verify that waste is being taken to treatment plants.

Second, treated wastewater should not be discharged into drains that run through unauthorized colonies. These drains end up mixing treated and untreated water, undoing the benefits of treatment.

Also read: AAP alleges ‘fake’ Yamuna ghat made for PM Modi; BJP hits back

Third, Delhi must reuse its treated wastewater. The city’s groundwater levels are depleting rapidly, yet treated water is barely being used. Only a small fraction goes to horticulture, irrigation, or industries. Malls, for instance, often face water shortages while being located close to STPs. This treated water can be redirected for reuse.

Lastly, Delhi needs to restore its lakes to recharge groundwater and prevent urban flooding. Most city lakes are dry, according to the Delhi Parks and Gardens Society. Refilling them with treated wastewater can revive them, recharge aquifers, and absorb excess rainwater during storms—a win-win solution.

If these steps are taken, the Yamuna can indeed be cleaned. But the focus must shift from building more plants to managing the wastewater system as a whole.

The content above has been transcribed from video using a fine-tuned AI model. To ensure accuracy, quality, and editorial integrity, we employ a Human-In-The-Loop (HITL) process. While AI assists in creating the initial draft, our experienced editorial team carefully reviews, edits, and refines the content before publication. At The Federal, we combine the efficiency of AI with the expertise of human editors to deliver reliable and insightful journalism.