• Gautam Dayal

Why does Bellandur Lake catch fire, froth? IISc scientist Dr. TV Ramachandra talks…

Updated: Nov 13, 2020

Why does Bellandur Lake catch fire? Lakes and water are supposed to put out fires and not catch fire. The recent fire in Bellandur Lake in January 2018 raged for 7 hours and demanded more than 5,000 army men to douse it. What really happened?

Why does Bellandur Lake froth?

Sunday, February 25, we met with Dr. TV Ramachandra (Dr. TVR), an eminent scientist from IISc (Indian Institute of Science, Bangalore) in his office to try and solve this puzzle. Everyone in the Bellandur Lake circles knows Dr. TVR and he is the authority on the lake. He heads the Energy & Wetlands Research Group in the Centre of Ecological Sciences at IISc and his lab has done in-depth studies and written countless papers about environment from Bellandur Lake to the Western Ghats. We have combined information from his interview and also read some of these informative papers to try and understand these tricky issues.

What are the reasons for Bellandur Lake catching fire?

The 2015 fires were caused by the hydrocarbons from industrial waste. For example, petroleum is a hydrocarbon. These hydrocarbons are highly flammable and float on water, which is why the 2015 fires followed the same line as on which the industrial waste flows.

The recent 2018 fires were caused by chemicals in the sewage that flow in Bellandur Lake at 500 mld (million liters per day).

We know that 40% of Bengaluru’s sewage enters Bellandur Lake, and most of it is not treated. This means that it is rich in phosphorus, which comes from detergents, and nitrogen, which comes from human waste. These nutrients are the same ones that are used in fertilizers, and cause rapid growth in the macrophytes of Bellandur Lake such as the water hyacinth. You may think this is a good thing, but it actually spoils the ecological balance and causes eutrophication that means excess plant life in water. These macrophytes grow and form a thick later on the water and eventually dry up, forming another layer of dead plants on top.

This growth of macrophytes causes a low dissolved-oxygen (DO) level in the lake that cannot support aquatic life such as plankton and fish. The macrophytes prevent sunlight from reaching the lake water that prevents the life from photosynthesizing which means no oxygen is given out. The macrophytes also prevent the oxygen from diffusing into the water from the air. All of these factors cause a low DO level in Bellandur Lake

The low oxygen level causes anaerobic activities: digestion and respiration that does not use oxygen. These activities release methane: a gas that is highly flammable and is used as a fuel.

Furthermore, illegal waste (domestic and construction) is dumped on the layer of macrophytes and that makes it even more toxic and easier to burn.

Finally, all it takes is a spark. The spark can come from a cigarette thrown, burning garbage grass, etc. The waste and dried up macrophytes easily catch fire that quickly spreads to the methane below. The methane is highly inflammable and causes the fire to spread around quickly. This is how the massive fires of 2018 happened.

Why does the lake produce toxic foam and froth?

The short answer is because of phosphates from detergents. Large amounts of phosphorus enter the lake, but plants absorb a tiny fraction of it. The remaining portion settles as sediments at the bottom of Bellandur Lake. When heavy rainfall or winds occur, the water churns and causes the phosphorus to come up (called up-welling). This causes the lake to foam and froth, just like detergent water that also contains phosphorus.

Some other countries such as the USA had a similar problem in the 1970s, but they immediately banned phosphate-based detergents and used other alternatives. This solved the problem. In India, there is a proposed legislation in the parliament to ban phosphates from detergents. We should push for it!

The biggest problems with Bellandur Lake

Firstly, very few buildings and factories have functional STPs (Sewage Treatment Plants). This means that the sewage that enters Bellandur Lake is untreated and toxic. Also, the detergents we use are rich in phosphorus that leads to the carcinogenic foam that the Lake spews. Moreover, Bellandur Lake’s wetlands, which could have been invaluable in cleaning the lake, have already been encroached upon by several builders. The plants in the wetlands could have been used to absorb most of the nutrients before they reached the lake itself.

Some Solutions

  • Ban phosphate based detergents as this will stop foam and reduce fire.

  • Apartments should have proper STP (sewage treatment plants) at primary and secondary level.

  • Aim to have tertiary STPs.

  • Increase wetland cover to help the lake.

Message for today’s youngsters

We also asked him if he had a message for today’s youngsters, pat came his reply: “Do not be a slave to your mobile phones. Exercise your brain: do simple calculations in your mind—remember the date.” Luckily when he quizzed me on the day’s date I remembered it, but I still wasn’t sure if I was right. He also urged youth to read more about the lake and understand the issues.

On a Personal note

When asked why he became an environmental scientist, he said that he enjoys the interdisciplinary nature of his work since environmental sciences are at crossroads of chemistry, biology and engineering. He works on Sundays, and when we asked him what he likes to do in his free time, he mentioned that he has no free time.

More power to Dr. TVR and people like him that work so hard to save our environment!

Here is a link to IISc research papers on wetlands and lakes

Please comment below if you have any questions or you can add to this. We welcome all information and discussion.


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