Air pollution | How well do Delhi’s giant smog towers combat bad air?

Inaugurated by Delhi CM Arvind Kejriwal on August 23 and functional since September 22, the Smog Tower in Connaught Place is touted as India’s first large-scale urban air cleaning facility. (Image : Gulam Jeelani)

The giant smog tower off Baba Kharak Singh Marg, near the Shivaji Stadium metro station in Connaught Place, is yet another landmark in central Delhi.

The 78-feet (around 24 metre) high structure uses a state-of-the-art filtration system to suck in polluted air with 40 fans, purify it using 5,000 filters and push out clean, breathable air.

Inaugurated by Delhi Chief Minister Arvind Kejriwal in August and functional since September 22, the tower, one of the two in the national capital, is touted as India’s first large-scale urban air cleaning facility. It is able to clean up to 1,000 cubic metres of air every second and helps clean the air within a one-kilometre range.

READ: Explained | Hiding behind a smog tower

“It has been installed on an experimental basis,” Kejriwal said at the time of inauguration.

Smog refers to the dirty brown haze that hangs over the skylines of major cities, including Delhi, and causes multiple health problems, particularly in the winter months.

Delhi’s second tower was inaugurated in Anand Vihar on the city’s outskirts by Union Minister for Environment, Forest, and Climate Change Bhupendra Yadav on September 7.

The towers were constructed after the Supreme Court last year gave the Union government a 10-month deadline to install two towers in the city, in compliance with a 2019 order.

On October 1, during a visit to the Connaught Place tower, Delhi Environment Minister Gopal Rai said that it had reduced air pollution in the vicinity by up to 80 percent, a claim questioned by experts.

Clean air on a hazy day

So, how effective a solution are these smog towers? Here is what MoneyControl found after visiting the tower in Connaught Place.

Also, read: Air pollution shortens Indian life expectancy by nearly 6 years: Study

At 10:30 am on November 3, the monitor installed atop the tower displayed PM 2.5 levels outside at 275.84 and PM 10 at 303.87. The controlled air quality, after purification, displayed PM 2.5 levels at 103.1 and PM 10 at 110.6.

This was on a day when Delhi’s air quality had deteriorated to the “very poor” category for the first time this season, with the overall recorded air quality index (AQI) over 310, according to the Central Pollution Control Board.

Since October 31, Delhi Chief Minister Arvind Kejriwal has been sharing the overall AQI and the levels of PM 2.5 and PM 10 recorded in the national capital on his Twitter handle.

02 Nov -

AQI - 303 (200 to 300 - Very Poor)

PM10 - 287 (251 to 350 - Poor)

PM2.5 - 139 (121 to 250 - Very Poor) https://t.co/rzSVGbCY2c

— Arvind Kejriwal (@ArvindKejriwal) November 2, 2021

No evidence

The bad air worries multiply ahead of Diwali. BJP leader and municipal corporator Sandeep Kapoor visited the Connaught Place smog tower on November 4.

“You cannot measure the impact of a a smog tower if it is installed in a vicinity that is already less polluted due to greenery,” said Kapoor, noting that he is an engineer by profession.

The concept of smog towers, which works on the principle of HEPA (High Efficiency Particulate Air) filtration or air ionisation technology to remove PM 2.5 particles, was popularised in 2016 when a 100-metre tall tower was built in China’s Xian city.

The patented air-cleaning technology was developed by Regents Professor David YH Pui and his research team in the Department of Mechanical Engineering at the University of Minnesota in the United States. In India, the towers were modified by IIT-Bombay and IIT-Delhi to track pollution levels at the inlet and outlet. The local customisation design and construction of the towers is managed by Tata Projects Ltd, which has outsourced its maintenance.

Also, read: North India’s air pollution concerns return as stubble burning resumes in Punjab and Haryana

“It’s (the CP tower’s) inauguration by Delhi's Chief Minister demonstrates the commitment of his government to explore new technology to solve the PM 2.5 air pollution problem in Delhi,” Charles Lo, from University of Minnesota, told Moneycontrol in an email on behalf of Professor Pui.

The IITs are studying the effectiveness of the tower in a pilot study that will also determine how the tower functions under different weather conditions.

“If the study by the IITs, which may take a year or more, finds it successful, then we can install a number of low cost towers using similar technology across Delhi,” Khan said. The tower has so far resulted in expenses of about Rs 20 crore for the Delhi government. Of this, Rs 13 crore was spent to install the tower.

The tower, Khan said, is certainly not a solution to combat air pollution but is more like a ‘clean air breathing park’. “Pollution has to be controlled from the source itself as an effective solution to bad air,” he said.

Delhi needs 100 towers

Professor Pui has estimated that if Delhi builds 100 towers over the next few years, this technology could curb PM 2.5 concentration by about 50 percent, according to a report in the University of Minnesota.

Delhi is one of the worst polluted cities of the world. The city's annual PM 2.5 average for last year was around 17 times the new World Health Organisation -recommended safe annual limit of 40 micrograms per cubic metre.

“These towers will by no means solve the problems of PM 2.5 and carbon dioxide pollution entirely — the end solution hinges on encouraging governments to invest in sustainable technology,” Professor Pui was quoted as saying in the report "Curbing air pollution with purification towers".

Though Professor Pui and his research team have claimed that the first tower in China has been cleaning air at the rate of 17 million cubic metres per day, there has not been any data to back the claim that the tower entirely helped reduce pollution levels, according to many reports. The tower in China has been slammed by experts and national media as an ‘eyewash’ and ‘ineffective’.

“While smog towers might come across as a visible solution to air pollution, there is no scientific evidence — even globally — to support that they can filter outdoor air effectively,” Tanushree Ganguly, programme lead at the Delhi-based Council on Energy, Environment, and Water (CEEW) told news agency PTI.

The average Indian life expectancy is shortened by 5.9 years due to air pollution, compared to what it would be if the WHO guidelines were met, a global study released on September 1 had said.

“Smog towers, if designed with good, cost-effective and long-lasting filtration technology, will definitely help in curbing the already high outdoor air pollution,” said Kartik Singhal, Founder of O2 Cure air purifiers.