Using sunlight to purify water

[Gorge]

This is an interesting news article about Tanzanian villagers who use the sun to sterilise dirty water
http://news.bbc.co.uk/1/hi/world/africa/4786216.stm

 

[g4ghb]

interesing.... however call me a sceptic i'm not sure it would work too well in the UK........

 

[tomtom]

like a lot of these things which use sunlight it is probably a lot more useful if you live a bit nearer to the equaiter than most of us do.. but its an interesting topic.. thanks Gorge..

as a side note.. i read a book sometime ago called 'a parrot in a pepper tree' about a guy who moved to spain to run a farm.. in this book (his second) he built an 'eco folly' a kind of pond/swimming pool with no chlorine.. as part of the filtration system the water flowed slowly in a thin layer over a sheet of meral or plastic where it could recieve a good ammount of sun light.. it was also passed through reed beeds and sheeps wool if i remember correctly..

 

[andyn]

I havent read the article, so i may be repeating some of it, but correct me if i'm wrong but doesn't the UK use UV light to purify drinking water?

 

[Ogri the trog]

I havent read the article, so i may be repeating some of it, but correct me if i'm wrong but doesn't the UK use UV light to purify drinking water?

Never mind the rest of the country, we have a UV capsule as part of the treatment system for our well water

ATB

Ogri the trog

 

[anthonyyy]

“The only thing you have to do is to paint a PET bottle with a special black paint which converts the sun’s rays into heat. If you fill this kind of bottle with water and let it sit out in direct sunlight, the temperature in the bottle rises quickly resulting in the bacteria being killed off. After an hour and a half the water reaches a temperature of 70° C and four hours later it is completely disinfected thanks to the increase in temperature and the UV impact.”

http://www.groept.be/T/ENnews/2002_2003/121_13_aerts.htm


I suspect that, in high summer, the technique would work in out latitudes. I have also heard of it working just using a PET bottle without painting it. The combination of heat and UV is pretty effective.

 

[bushtuckerman]

tomtom, your side note reminds of Driving Over Lemons...can't remember who it's by, but i remember it being pretty good, i think i watched a televised version, but my mum liked the book. it's about a guy who ups ship and migrates to spain to buy a farm. someone on here must have read it and has more info...anyway, well worth a read i would imagine, for bushcrafters or anyone.

edit: just noticed you said that was his second book, i think driving over lemons must have been his first!

 

[tomtom]

tomtom, your side note reminds of Driving Over Lemons...can't remember who it's by, but i remember it being pretty good, i think i watched a televised version, but my mum liked the book. it's about a guy who ups ship and migrates to spain to buy a farm. someone on here must have read it and has more info...anyway, well worth a read i would imagine, for bushcrafters or anyone.

driving over lemons was his first book.. the guys name is Chris Stewart they arnt strictly bushcraft but i enjoyed them both!

never heard of a tv version.

 

[bushtuckerman]

snap! i may be wrong about the tv version, maybe a film? i dunno, i have a dodgy memory...come to think of it, i did read an extract in my GCSE English Lit paper! i seem to remember liking it too much and missing the point of the question...

 

[singteck]

I am from the tropic and i can say that sunlight poses another problem to water purification. Put the water too long in the sun and you will get algae growing in it. Green water is not my cup of tea.

singteck

 

[NickBristol]

I'm sure I've posted about this b4 but can't find it anywhere...

Anyway, I've seen sunlight being used in a few places around the world to sterilise water. I think one of the major water charities provided the equipment but don't quote me on that...

The basic setup is similar to the domestic solar heated water panels that are sometimes found on roofs in the UK, except that the glass (and it was always glass too btw) panels are clear both sides, with perhaps a one inch gap between the panes. It reminded me of double glazed glass patio doors sealed on all sides and tilted to be south facing. There was an inlet tap at the top fed by a large water butt and at the bottom was an outlet tap which either ran to pipes or more often a standpipe. As the water does stay standing for long, algae build up never seemed to be a problem... Didn't much like the warm water that comes out the end but rather that than getting sick

 

[PC2K]

i have read this before, if you not close to the equator, forget it! It not only uses UV radiation, but also heat. It's this combination that makes the water safe. We don't get enough UV radiation or heat from the sun in europe.

 

[Wayland]

I've been keeping an eye on this kind of thing for a while.

Anyone heard anything about them?

 

[Nemisis]

While i've not used one from the reading it seems to kill the bugs but theres nothing about chemical filtering heavy metals etc so presumably you'd need a carbon filter method to? The other thing 60 litres per pair of batteries average price around £10 per pair seems expencive.
Dave.

 

[oracle2]

more on this subject here

http://www.sodis.ch/Text2002/T-Howdoesitwork.htm

 

[bushtuckerman]

would UV radiation ionise impurities in the water at all? and also, i don't want loads of free radicals kicking about in my water either!..?

 

[anthonyyy]

more on this subject here

http://www.sodis.ch/Text2002/T-Howdoesitwork.htm

Very good link.
I see no reason why this method should not work in these latitudes in summer. After all, in summer we have much longer days than tropical regions. 50 degrees C for an hour is quite easy to achieve using the method given in the link. Turbidity is a major factor, so letting the water stand and decanting it should improve the effectiveness.
Of course this method only sterilizes water, chemical contamination is not addressed.

 

[Chris Thompson]

I am from the tropic and i can say that sunlight poses another problem to water purification. Put the water too long in the sun and you will get algae growing in it. Green water is not my cup of tea.

singteck

Not to mention that some (all?) types of algae are poisionous in high concentrations. Plus it tastes funny!

Putting any black plastic bottle in direct sunlight for the day (in hot sunny weather) will bring the temperature up enough to kill any bacteria, and being black will stop algae growth. A good thing to remember if you're lost in the bush without a suitable container to boil water. - Army water bottles are ideal.

 

[KIMBOKO]

UV (C) light has been used for disinfecting fish ponds for many years. You can buy the same UV(C) lamp as used by http://www.uvaquastar.com/ and fit it where a normal florescent tube would go in a "camping torch". In essence the same product. I just need to find out how to check to see if the UV is doing its job. Anyone in the water industry or work in a lab with water based pathogens?.

A different idea but still on the theme of water. There is a lot of interest in using colloidal silver and ceramic or fine ceramic grog filters in the the third world as an effective way to treat water. Backwoods type filters or a clear source of water could easily treated with colloidal silver made on the spot (electrolysis using battery and pure silver) this would be another way of treating water. I would like to experiment but again need to find out more about testing treated water.

 

[PC2K]

read more here:
http://almashriq.hiof.no/lebanon/600/610/614/solar-water/unesco/35-46.html
http://www.sodis.ch/
http://solarcooking.org/sunandwater.htm