Wastewater crisis brews in Bengaluru’s backyard

The sewage treatment plant attached to the Tippagondahalli reservoir lacks the capacity to treat the sewage water coming into the reservoir.

Rivers in and around Bengaluru that once were clean and clear have become the channels that carry industrial effluents, domestic sewage, and disintegrating solid waste from the city’s sprawling urban-industrial catchment.

Bellandur Lake, located on a tributary of the Dakshina Pinakini River, gained worldwide infamy for its foam and fires. Similarly, Kelavarapalli Dam on the Dakshina Pinakini and Byramangala Dam on the Vrishabhavathi River in Ramanagara are infamous locally for the massive foam that occasionally engulfs roads. These foaming rivers are not just an eyesore—they are stark indicators of collapsed ecosystems, putting our most essential resource, clean drinking water, at grave risk.

With each passing year, both the pollution crisis and the city’s drinking water crisis intensify. The government and policymakers continue to focus on costly and unsustainable projects to source drinking water from west-flowing rivers like Netravathi and Sharavathi, located even farther from the city. Pollution prevention and mitigation have taken a backseat.

A classic case in point is Thippagondanahalli Reservoir (TGR), built on the Arkavathi River and commissioned in 1934 to supply drinking water to Bengaluru. As the catchment area developed due to urbanisation, industrialisation, monoculture plantations, and agriculture, it severely degraded. The river’s flow gradually dwindled; by the 1990s, it had dried up.

After decades of neglect, the government issued a TGR preservation notification in 2003 to protect and preserve the catchment. However, since the notification remained on paper, what was once a dry river began to flow 365 days a year with toxic wastewater. As a result, by 2012, TGR, the last remaining drinking water reservoir close to Bengaluru, was abandoned.

The wastewater issue

Yettinahole Drinking Water Project, which sources water from the distant Netravathi River at an estimated cost of Rs 23,251.66 crore, involves the construction of eight dams to store water, which will then be distributed through an 873-kilometre network of pipelines. The project will require an immense 370 megawatts of electricity to pump water across this vast infrastructure.

This project intends to provide 24 tmc of water to the parched districts of South Karnataka by filling several hundred lakes and reservoirs, including TGR, which has been allocated 1.8 tmc. If TGR is to receive fresh water from Netravathi, then what happens to the wastewater flowing in the Arkavathi River, reaching TGR?

To understand how much water flows into the reservoir, Paani.Earth, a Bengaluru-based organisation that works on rivers, took twenty-four-hour flow measurements on March 24, 2024. The data revealed that approximately 163 MLD of wastewater enters the reservoir daily on weekdays.

Field investigations identified a 20 MLD Sewage Treatment Plant (STP) at the Arkavathi River inlet of the reservoir. If the STP operates at full capacity, it can reduce wastewater flow by 20 MLD. However, this still leaves 143 MLD of untreated wastewater entering the reservoir daily.

This 143 MLD of untreated wastewater amounts to 1.8 tmc annually—equal to the 1.8 tmc of clean water that TGR is slated to receive from the Netravathi River under the Yettinahole Drinking Water Project.

This means that, instead of being a source of clean water, the 1.8 tmc of fresh water brought in at a significant cost across vast infrastructure will inevitably be polluted by the ongoing flow of untreated wastewater.

Usually, when a lake or tank is rejuvenated, a common strategy is diverting sewage or wastewater entering the lake to downstream water bodies. A notable example of this is the diversion of the Vrishabhavathi River at Byramangala Reservoir.

However, in this case, diversion is not a viable option. Just ten kilometres downstream lies the Manchanabele Dam, a critical drinking water source for Ramanagara city and surrounding villages, with plans to extend its supply to Bengaluru. Diverting wastewater into this dam would pollute another vital drinking water source, making this approach impractical.

The government has reportedly tasked experts with suggesting nature-based solutions to address 20 MLD of polluted flow during the monsoon. But what about the 143 MLD of toxic wastewater that flows into the river daily? This points to a disconnect between the scale of the pollution problem and the government’s response.

By ignoring the remaining flow, the government is either underestimating the true extent of the crisis or deliberately avoiding the difficult steps needed to address the full scope of the issue.

Handling non-biodegradable pollutants

Nature-based solutions are the latest buzzword and are projected to be excellent solutions. But no one has bothered to check if they truly work as a solution to the polluted water in Arkavathi.

In 2010, the Central Pollution Control Board declared the Peenya Industrial Area, located in the catchment of Thippagondanahalli Reservoir (TGR), severely polluted.

In 2018, the Karnataka State Pollution Control Board sealed 31 borewells in the region after discovering dangerous quantities of hexavalent chromium—a synthetic carcinogen and reproductive toxicant—in the groundwater. A significant amount of toxic water flows from this industrial area into the Arkavathi River.

But it is not just hexavalent chromium—the industrial-urban complex generates a wide range of synthetic substances, including microplastics, endocrine disruptors like triclosan, Bisphenol A, and phthalates, as well as organic pollutants such as dioxins and furans. These chemicals are present in everyday products—triclosan in toothpaste and handwash, Bisphenol A and phthalates in plastic containers and packaging, and so on.

Excessive consumption, combined with the indiscriminate dumping of domestic and industrial waste, has led to the unchecked spread of these substances in rivers and reservoirs. These synthetic chemicals accumulate in the water and magnify through food chains because they are not biodegradable—nature cannot break them down. How can nature-based solutions effectively address this issue if nature cannot biodegrade these pollutants?

These non-degradable chemicals are a global problem. The release of synthetic substances into the environment without adequate testing has surpassed safe levels worldwide, as confirmed by international scientific assessments. In Bengaluru, the foaming rivers tell us firsthand that the safe limits were breached long ago.

Containing the contamination

It is time to recalibrate the thoughts and actions that decide pollution parameters in Bengaluru. It is important to shift from relying on post-contamination solutions to prioritising contamination prevention.

This means preventing industrial effluents, solid waste, and sewage from entering our rivers.

Prevention is, by far, the most effective method of cleanup. It is enshrined in the Water (Prevention and Control of Pollution) Act 1974, underscoring the need for proactive measures to safeguard our water resources.

Prevention does not require new technology. Enforcing existing regulations and targeted actions, such as removing phosphates in detergents and banning harmful chemicals like triclosan, helps.

Most importantly, prevention requires a collective will—political, corporate, and societal—to act and strengthen water pollution governance. Without this unified effort, the drinking water crisis caused by pollution at TGR will persist and worsen with each passing day.

(The author is the co-founder of Paani.Earth, based in Bengaluru)