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Current IssueApril 25, 2015
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Ask The Expert: Recycling water from your ACvv
Question: Q: I am a third year polytechnic student in Asia. My project title is "Recycle water dispensed from air-conditioners to (potable) drinking water." We will be targeting the industrial side for the collection and recycling of water and water dispensed from the air conditioning systems will be collected in a tank. Filtration will be carried out and treated water will be stored in a tank before drinking. What are the possible contaminants in the air-conditioned water? What are the possible ways to prevent recontamination if the water is to be stored in a tank after filtering? A filter company had recommended reverse osmosis. But the water ratio is 5:1. As our aim is to save water, this is not found to be suitable. My budget is about $500-$650. For my case, would you recommended a carbon+UV filter or reverse osmosis? Do I need to add additional chemical to the water to improve the mineral content of the water for drinking? Hope to receive your reply soon.

Calvin Wong,

Answer: A: As with water sources, the contaminants in air vary considerably from one location to another, depending particularly upon proximity to industries that may be a source of air pollution. Water condensed from the air may be of fairly potable quality or it can contain hazardous chemicals, including particulate of lead oxide, volatile organic compounds, oxides of sulfur and nitrogen, and even ozone. To be sure these all are effectively removed, a combination of activated carbon adsorption and reverse osmosis should be used for the highest purity. Yes, reverse osmosis does discharge a waste stream, but keep in mind that this stream also is discharging the vast majority of contaminants that may have been present in the air and, thus, were removed from the water. It may be possible to dispense with the reverse osmosis technology, but testing will be required to determine what exactly is in the condensate. A disinfection technology such as UV is recommended, because stored water will grow bacteria. To prevent recontamination in the storage tank, you can also add chlorine to a residual level of 0.5 mg/L. The storage tank should be constructed of a material that does not contaminate the water and has a good cover. As a final step, I would run the water through a point-of-use carbon filter to remove any taste or odor it may have picked up.

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