In January this year, the Supreme Court has directed that two smog towers should be installed in the capital by April on a pilot project basis considering a proposal by the IIT-Bombay.

Try this question from CS Mains 2015:

Q.Mumbai, Delhi and Kolkata are the three mega cities of the country but the air pollution is much more serious problem in Delhi as compared to the other two. Why is this so?

What is a ‘Smog Tower’?

• A smog tower is a structure designed to work as a large-scale air purifier, fitted with multiple layers of filters which trap fine dust particles suspended in the air as it passes through them.
• Air is drawn through fans installed at the top of the tower, passed through filters, and then released near the ground.
• The large-scale filters expected to be installed in the towers in Delhi would use carbon nanofibres as a major component.
• It would be fitted along the peripheries of the towers and the height would be 20 metres.

How does it work?

• The 20-metre (65 feet) high tower will trap particulate matter of all sizes suspended in the air.
• Large-scale air filters shall draw in the air through fans installed at the top before passing it through the filters and releasing it near the ground.
• The filters installed in the tower will use carbon nanofibres as a major component and will be fitted along its peripheries. The tower will focus on reducing particulate matter load.

Has anyone else experimented with a smog tower?

• Yes, smog towers have been experimented with in recent years in cities in the Netherlands, China, South Korea and Poland.
• The first such tower was erected in 2015, in Rotterdam, Netherlands, created by Dutch artist Daan Roosegaarde.
• The towers to be installed in Delhi are to be the result of a collaboration between the IITs at Mumbai and Delhi, and the University of Minnesota.

Why New Delhi?

• Air pollution in the national capital has been an issue of concern for quite some time as Delhi and its suburbs have ranked among the most polluted cities in the world frequently.
• In 2014, the World Health Organisation (WHO) had declared Delhi the most polluted city in the world.
• Pollution levels in Delhi increase dramatically during winter — on some days to nearly 10 times above the limits prescribed by WHO, posing a serious risk to vulnerable and also healthy populations.
• This is large because sources of emissions — construction work, industrial and vehicular pollution — in and around the city remain more or less consistent.
• The situation is aggravated at the start of winter by smoke from stubble-burning in northwestern states, coupled with unfavourable meteorological conditions, such as calm winds, low temperatures, and fewer sunny days.

How effective are smog towers?

• An estimate on air quality shows that a tower would reduce 50% of the particulate matter load in an area of 1 kilometre in the direction of the wind, as well as 200 metres each along the sides of the tower and against the direction of the wind.
• In an open field in calm weather, it can reduce the particulate matter of 10 micrometres (PM10) up to 45%, and PM2.5 levels up to 25% in an area of 20 metres around the tower, as per details on the ENS Clean Air website.

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