Solar Water Purification
March 27th, 2006
Villages in Tanzania are using the sun’s rays to purify their drinking water, saving time and energy. Pastor Moses Kwanga is behind the project, which aims to educate rural populations on this easy way to purify their water supply.
The sun heats the water, helped by the black roof, which helps to absorb the heat. Solar radiation means a combination of ultra-violet rays and heat destroys the bacteria which cause common water-borne diseases like cholera, typhoid, dysentery and diarrhoea. After eight hours in the sun, it is ready to drink. If the water reaches more than 50C, it is safe in just one hour.
Link via BBC
You would think that if this were a reliable way to purify water, it would be more widespread. Why is Dean Kamen spending so much time and money on a powered water purification system? Granted, it runs off of cow dung, and generates 1000 liters of water per hour, but it will still cost a lot to manufacture each unit.
Related Posts: Water Filters for the 3rd World, Solar Oven from Wind Reflector
March 27th, 2006 at 4:57 pm
Intuitively I doubt that heating water to a mere 50 degrees will kill everything or even make most water potable. Just off the top of my head bacillus cereus, thrives in boiling rice water, in fact anyone who has gotten ill from chinese take-out likely it was from the rice water in which was boiled. Granted heating the water to 50 C might kill the species responsible common causes of morbidity/mortality, but i sadly doubt that it “purifies” everything.
For those people’s sake, I would love to be proven wrong.
March 27th, 2006 at 5:17 pm
It wasn’t the temperature – it was the UV they’re saying sterilizes the water – details in the article body.
March 27th, 2006 at 6:58 pm
I can’t believe the price tag these systems come with: currently $100,000 with goals to make it $1-2,000 a piece.
Since an average third world citizen’s wage is no more than a few dollars a day (if that), this better be strong enough to handle the water supply of a whole village.
I’m glad, however, that more people are finding this a worthy cause to take on. Unsanitary water is one of the leading causes of avoidable death in the world right now, particularly in children.
Learn more:
UNICEF
World Health Organization
March 29th, 2006 at 8:42 pm
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July 10th, 2006 at 8:17 am
Just a thought, although I know I’m a couple months late.
“Why is Dean Kamen spending so much time and money on a powered water purification system?”
Because no amount of sunlight will filter out a dead bug floating on top of the bottle. This will only eliminate bacteria, but I would imagine there’s a lot of other stuff in water systems that needs to be eliminated.
November 25th, 2007 at 10:43 am
Fill an empty 2L water bottle and leave in the sun will accomplish the same thing virtually for free…but people don’t seem to value something because it is free…”too good to be true”.
To make the maximum amount of profit from this situation, the entrapreneurs transfrom the “free” water bottles method into a “high-tech” solution and charge just under what the market will bear.
Sadly this is what makes the world go around.
Regards to all,
DaveZ
January 25th, 2008 at 8:46 am
Interested in this theory. Where can I find more information?
January 28th, 2008 at 7:44 am
Hi, Ian – Dead bugs are mostly not harmful… unless it’s a poison bug or something. I wouldn’t eat a wasp, for example, what if I pricked my tongue with its stinger? Not sure if that can happen.
However non-bacterial contaminants are definitely important… a serious issue is heavy metals, but especially in urban waterways, drugs are an issue. Wasn’t there some report of hermaphroditic, mutated fish being found in the Delaware river, due to something humans were putting in the water? Pharmaceuticals or something? The person to ask about this is Natalie Jeremijenko.
Still, most rural water sources are only problematic because of bacteria. That’s why so many filtration systems use a simple carbon filter or UV rays.
March 24th, 2008 at 3:28 pm
Leaving water in the sun will not remove arsenic from it. The SlingShot (Dean Kamen’s new Water Purification System) will remove heavy metals from the water. Distilled water “tastes” so good, I wish I had access to a device like that.
BTW a SlingShot purifies 1000 liters of water a day (not an hour).
March 28th, 2008 at 8:26 pm
I can’t believe no one is seeing the value of tapping the huge amount of ocean water that is salty and will not be changed by some sun, or heat or UV. The oceans offer an unlimited supply of water that is too expensive to distill by simple heat. That is what is so wonderful about Kamen’s water purification machine.
April 11th, 2008 at 6:21 am
stick water in clear plastic bottles and it purifies it. it won’t get rid of heavy metals. if you had compost worms about, you could pour the water through the bedding for about 6 weeks, which would leach out the heavy metals, then purify the water in the clear plastic bottle – of course, you would need a way to reticulate the water, and a supply of worms, as well as a ubiquitous bottle.
rather than spend $1000 on a machine which needs energy to purify (and the cow dung would be better put to food production via composting in the soil) buy a water capture unit – the technology can run on solar power and captures water in the air. with around 35% humidity about 24 L are produced per day, right down to 11% humidity producing 6 L per day.
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