First the headlines: A girl dies of heatstroke after spending four hours to collect water on a hot day from a hand pump in Maharashtra; Tikamgargh municipality in Bundelkhand hires gunmen to protect its sole water body from being used on the sly by farmers in Uttar Pradesh; people and courts debate the pros and cons of holding cricket matches on pitches that require extensive use of water in the midst of a drought and heatwave.
Next, a common scene in the city this year: Electronics dealers in Tiruchi start their summer sales early – and hire out party halls to showcase the latest air-conditioners. The appliance has become cheaper than a two-wheeler, and therefore, affordable to a new stratum of consumers. Almost overnight, the scorching summer sun has melted the air-conditioner’s image as a luxury item and repositioned it as a necessity.
“Global warming, water scarcity and air-conditioning are all inter-connected,” says S. Senthil Kumar, Science and Engineering Research Board (SERB) Scientist Fellow and associate professor at the PG & Research Department of Biotechnology of National College, Tiruchi.
“You cannot stop people from using air-conditioners to deal with the heat, even though these gadgets play a role in warming up the atmosphere. At the same time, you also need to figure out how to deal with chronic water shortage with something more than the existing natural resources,” he adds.
Ironically, the air-conditioner could itself be a handy tool in this effort, says Dr. Senthil, who has spent 5-6 years studying how to reuse the distilled water or condensate that flows out of the appliance after the atmosphere is cooled and dehumidified. He has also applied to the Department of Science and Technology for funding for this project.
A useful nuisance?
“It’s not rocket science,” says Dr. Senthil, “Air-conditioner water is considered a nuisance by engineers and builders. But when we have gone to the level of examining the potential of textile dye effluent as recycled potable water, then why not look at air-conditioner drainage?”
Moisture in the air (or humidity) is an invisible source of water that requires greater study, says Dr. Senthil, who will be presenting a paper on recylcling air-conditioner condensate at an international conference in Colorado College, Colorado Springs, U.S.A, in June. He was awarded the Tamil Nadu State Council Young Scientist Fellowship in 2015.
“India’s tropical climate ensures that there is around 60 per cent humidity in the air, which makes the rate of water recovery from air-conditioners high, especially in coastal cities like Chennai,” he says.
“In our lab here, I have found that we can get 8-9 litres of water per day from a standard 1.5 tonne split air conditioner. And we haven’t spent anything extra on extracting this water, nor touched the conventional water sources.”
Currently, all the condensate of the air-conditioners in the department is collected in 20-litre jerrycans which is then used as an alternative for distilled water in experiments and research.
Technically, the air-conditioner condensate is distilled water, which lacks essential mineral salts. It is not safe for human consumption without biological treatment.
“To make this water drinkable, we have to ‘pollute’ it with saltwater, so that the ions are reintroduced into it. If we add 10 ml of regular tap water to 1 litre of distilled water, it becomes drinking water,” says Dr. Senthil, who had a sample of the lab’s condensate independently tested by a private facility in Tiruchi through 72 parameters to ensure its safety.
In any case, conventional distilled water made with groundwater is not cheaper. “You have to waste at least 100-120 litres of normal water to get 1 litre of distilled water in a conventional distillation plant, because water has to boil completely, vapour has to be chilled, and brought back as distilled water,” points out Dr. Senthil.
Corporate role
However, he agrees that initially at least, the concept may find more takers in the corporate sector. “We have seen in a survey that there are nearly 1,000 private and public buildings in Tiruchi that have installed air-conditioners of at least 15 tonnage capacity.
Theoretically, 80,000 litres of water can be extracted from an 8-hour working schedule per day,” Dr. Senthil says.
Air-conditioners in closed rooms typically produce less condensate because the compressors are less active once the air is cooled.
“But in a big showroom where the doors open and close constantly, and where the outside air is exchanged with the inside air, the compressor will have more work, which means there will be more water recovered. From saving water from natural sources, we now move on to zero-extraction water savings in an eco-friendly manner,” says Dr. Senthil.
Most big companies that rely on air-conditioned workplaces tend to channel the condensate directly into the sewers. “It almost looks like we are blindfolding ourselves in our search for water,” says Dr. Senthil.
“As just one example, we could easily stop using tap water for cleaning floors and switch over to the condensate instead. This will ease the burden on the municipal water lines and help us to save water for essential use.”
The concept has a wider future-proof potential than other technology-based products because the principle driving the entire process will remain the same, says Dr. Senthil.
Developing a filtration system to remove the algal and bacterial growths in the water will do wonders for its reuse, he adds.
So why hasn’t the idea been taken up more actively across the world?
“Possibly because it is not commercially attractive,” replies Dr. Senthil. “Nobody can patent filtration processes or machines, because they are already in use. This is a need-based concept, much like rainwater harvesting. It should appeal to your conscience if you want to adopt it.”
* * *
Fact file
* Air-conditioners, like refrigerators, use chemicals that easily convert from gas to a liquid and back again to transfer the heat from the air inside a room to the outside atmosphere.
* As the air passes through the air-handling unit’s cooling coil, its temperature drops. Added to the humidity of the outside and inner room atmosphere, condensate is formed.
* Untreated condensate can amplify airborne bacteria that can cause mass outbreaks of illness in places that use central air-conditioning.
* Options to disinfect condensate water and make it usable for human consumption include treating it with ultraviolet light, chlorine tablets, ozone injection, and boiling it to at least 140 degrees Centigrade to remove possible biological contamination.
