Jumbo Size Vacuum Cleaners to Purify Urban Air?

See the cartoon by Marc Roberts - "Waiting to Exhale" in response to our blog piece below (3rd, April, 2010) on installation of a giant vacuum cleaner in Delhi.

************

Recently, at the entrance of the Palika Bazaar in Connaught place, the Delhi officials unveiled a giant air purifier. The European manufacturer, System Life, and their Indian business counterparts claim that this is the next innovative approach to clean the air and it is here for the better health of Delhites. See Hindustan Times, and UK Telegraph.

For an ordinary person, who is breathing the polluted air at any of the junctions and along the major road corridors, while stuck in the congested traffic, this sounds like a miracle solution. The machine is here to suck bad air and spew out clean air, with a freshener.

Are the officials suggesting that it is OK to pollute, because we are testing an innovative vacuum cleaner to clean the air we breathe, instead of acting on the technical and policy options, which might even be cheaper and faster to implement?

Air pollution is rising problem in Delhi and the sources are many – inside and outside the city. Growing motorization, coupled with an absence of appropriate road traffic reduction strategy on major corridors, an ageing and ill-maintained public vehicle stock, a sizeable share of two-stroke engine technologies, absence of an efficient public transport system, and inadequate separation between working, living, and moving space, have all led to traffic congestion resulting in longer travel times, extra fuel consumption, discomfort to road users, degradation of the urban environment, and high-level of air pollution in Delhi.

The particulate matter with aerodynamic diameter less than 10 micron (PM10) (and the lesser sizes like PM2.5) is considered the most harmful and routinely average above 150 micro-gm/m3 during the day, when the national standard is 100 micro-gm/m3 and the international health standard is 50 micro-gm/m3 for PM10.

In Delhi, the largest gain in the air quality was observed at the peak of the CNG conversions of buses. And since, the air quality levels have declined gradually over the years, in the residential areas and along the major corridors. The slow moving traffic during rush-hours puts the environment and lives in high danger and consequently stretches the health facilities beyond their capacities. In 2009, the Central Pollution Control Board (CPCB) announced that Delhi is now the “Asthma Capital” of India.

The machine acts as a vacuum cleaner, with an air intake capacity of 10,000 cubic meters per hour and the manufacturer demonstrates that the machine is capable of trapping the harmful PM (for three size fractions) by approximately 70 percent of the air flow. The machine costs ~2.5 crores plus the maintenance.

10,000 cubic meters of air per hour..?

The energy budget needed to reach a significant level of clean air is huge and not realistic.

Air flow, even in study conditions, for a distance of 100m (the operating zone for the machine), a height of 10m (the air we breathe), and an average wind speed of 1 m/sec, translates to 100*10*1*3600= 3,600,000 cubic meters per hour !!

Of this, at a point, 10,000 cubic meters of air is purified per hour. Now, think of a city which is 30km x 30km, at least. How many of these do we need and how effective are they really going to be?

Is this a realistic solution or giving false hopes of doing something?

The air pollution studies in Delhi have shown that the road dust is a major culprit, due to active re-suspension of the dust along the roads. Most often, the dust along the major corridors is swept and piled up, which over the day, makes its way back on the road and adds to the re-suspension. Plus all the vehicular exhaust.

Why aren't the city officials responding by taking measures to reduce the dust? An immediate and cheap option is to cut the road dust. Instead of a vacuum cleaner, get some of the vacuum trucks with water sprinklers in the back to suck dust off the roads, sprinkle some water, so we reduce the re-suspension effects. A truck can cover as much as 40 km in two hours, especially in the morning hours, and might effectively reduce the exposure levels during the rush hour.

While this is an innovative and effective solution for indoor settings like tunnels and subway stations, I have my doubts for using a vacuum station in an outdoor setting like Delhi.

There is no silver bullet for improving air quality, which is a growing problem in a number of cities.

Mitigation is probably the best solution, if the goal is to reduce air pollution quickly and effectively. What Beijing officials did for Olympics was unorthodox, closing down industries and cutting down traffic for the two months, but the series of measures and the event itself gave a reason to think back and realize what is the footprint of the human activities (transport and industries) that we are experiencing in the form of air pollution and related health impacts. Same is true in case of Delhi and the coming commonwealth games.

We need to try everything from promoting the use of public transport, clearing the dust on the roads, changing fuel characteristics at the refineries, curbing garbage burning in the residential areas, and controlling emissions at the industrial stacks, before we can think of vacuum cleaners for outdoors !!

Also see

• Monitoring what we want to manage and mapping urban air pollution in Delhi
• Air Quality Index (AQI) examples across the world cities
• Urban passenger travel statistics in India
• Photochemistry of air pollution in Delhi
• Why ban autorickshaws in Delhi?
• How to Estimate Transport Modal Shares Using Minimum Information - Case Study of Delhi
• Air pollution and health benefits of metro system in Delhi
• Air pollution in Delhi
• Beijing to Delhi - Traffic problems highlighted
• Need to push for public transport in India