Guest Post by Willis Eschenbach
One of the joys of writing for this blog is that I can promote good ideas. Here’s one I just came across, thanks to a commenter on another post of mine. The idea is solar disinfection of water, or SODIS. Follow the link, lots of good info.
Figure 1. The SODIS method in graphical form.
The idea is bozo simple. Put water into a clear plastic bottle. Shake it up well to oxygenate it. Put it out in the sun. Six hours in the sun and the oxygen plus the solar UV kills diarrhea.
I mean, how great is that? Now that’s solar tech I can get behind 100% … plus it uses up old water bottles. And doesn’t require any chemicals. Brilliant. Get the word out. Kids’ lives are at stake.
w.
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Frank K. says:
May 15, 2011 at 8:34 pm
I speak as a chemist.
A minimum of research in this system could improve it and improve their chance for a better life.
The old European method of water purification was to add some sugar from malted barley and yeast. If it didn’t stink, it was safe to drink.
BPA – no worries. Those plastic water bottles start out as tiny miniatures which are then inflated to full size by highly pressurized super heated steam. I’m sure that any chemicals likely to leach out were consumed by those who would pay for bottled water when the safest water on the planet comes out of their kitchen taps for free. I find the notion that anything will leach out at +45C that didn’t leach out from super heated steam rather odd.
Turbidity – yup, that’s a problem. Let the water sit in a pail until it settles, then pour the clear stuff into the bottles… rocket science this isn’t.
It has been said that humanity can be divided into two basic groups: those that drunk bear and those that drunk tea. Or in other words, some societies sterilised their drinking water by brewing it and creating alcohol, others boiled the water.
Perhaps this is a third group?
Evian spelled backward is “naive”, ho, ho.
Our ancestors’ way of killing the wee beasties in water was to mix a bit of alcohol with it . . . or make beer, ale or “short” beer, that is carbonate it. Making wine is very easy to do, and last I looked, completely legal for your own consumption. “Drink a little wine for thy stomach’s sake”. Before our highly sophisticated public purification of piped water, by adding a bit of chlorine to it, drinking plain ole water might well result in death.
Paul H,
Following your debunking link, I found the “Agenda” strangely familiar.
Back to plastic I suppose. 😉
Copy and paste error:
In India, ……
Better in the long run to supply these people with piped potable water to let them get on with their lives.
Having lived a substantial part of my life in 3rd world countries – all I can say is this is brilliant. The water bottles are common where I lived, because the local untreated water can kill you (people pay almost any price to stay healthy). I got sick many times.
I am still bemused living in my native Australia at the resistance of the politically correct to plastic water bottles.
Brilliant, cheap and simple.
crosspatch says: May 15, 2011 at 9:41 pm
Add a drop of iodine and you can probably get rid of that last 25% and do a great dietary service for populations with a low iodine diet where goiter is common.
Good comment
Additionally letting the kids have and teaching that a bottle (and cup/spoon) belongs to them (property) and ONLY THEM serves to reduce x-infection that results in salmonella, shigella and cambylobacter etc.
I am not sure what UV does to giardia, a dust born cyst resulting in 3-4 sloppy diarrhoeal motions/day. I recall that UV filtering may not have decreased giardia outbreaks in the Australian desert communities, but can not be sure that this is the case.
Good post Willis.
Geoff Sherrington http://wattsupwiththat.com/2011/05/15/sodis-roolz/#comment-661188
Soho pump was pumping shitty water out of the Thames due a gross system where effluence mixed with the water for human consumption http://www.lavoisier.com.au/articles/climate-policy/garnaut/Curtin-the-science-of-climate-change-and-carbon-taxes.pdf (source Lavoisier Society)
Fluoridation of the water supply decreases tooth decay, a major factor in heart disease and dental disease leading to other diseases of kids.
Kids at school (they have survived 0-5 yr time-line for some reason) are more likely to be provided with sanitation, clean drinking water, nourishment, personal safety and THEIR OWN INDIVIDUAL PROPERTY (toothbrushes, mugs, pencils, privacy and clothes etc).
Providing safe and drinkable water by such a simple technique is a useful enterprise as Willis points out.
Jimbo:
Thankyou for your comment to me at May 15, 2011 at 4:51 pm.
I have seen the method being used in several African and South American countries but – as you say – that does not mean it is in use in every place where it could provide a benefit.
I am grateful for your correction of my observation. As is always true for eveerybody, my personal anecdote is limited by my personal experience.
Richard
This temperature limit could be easily exceeded with a minor change in the solar exposure configuration. You would only need a small amount of concentration of the sun to reach that temperature.
Any sort of trough reflector setup could easily double or triple the solar concentration on the bottles. Trough reflectors located so their optical axis is a few degrees below the suns local noon time altitude in tropical climates should reach those temperatures with no difficulty. The higher solar isolation at the bottles location in the apex of the trough would also shorten the exposure time necessary to achieve required UV exposure, and help compensate for days with high overcast conditions.
A trough reflector concentrator is simply two reflective sheets placed to form an accute V shape with the central axis of the V pointed toward the noon day sun , with the long axis of the V oriented east to west. In that configuration the day time sun would be shining down the V and the solar isolation at the bottom of the V would be any where from 2x to 10x the day time noon sun intensity, depending on how large the plates are. Commonly trough reflectors are designed as parabolic reflector troughs but for this situation that would be the hard way to do it.
Much easier to build from local materials would be a simple V trough reflector as in this image.
http://img811.imageshack.us/img811/3161/sodistrough.gif
Putting a top cover of a thin sheet of plastic over the bottles to help insulate them in an inclosed box would also help increase the stagnation temperature of the water.
Interesting that the “Deniers” of this process 100% ignore the fact that it works and has minimal associated expense. Dredging up the null hypothesis: What if this process didn’t work at all? Then the consequences would be dead children and heart broken parents.
This method is a beautiful example of going with an imperfect but working solution while waiting for an affordable perfect solution to be discovered. I have no doubt that blink charts of deaths caused by chronic exposure to diarrhea vs chronic exposure to leached chemicals will favor this solution. Given a choice I will take the plastic tea every time. Meanwhile, hopefully the hand wringing SODIS deniers are spending all their free time finding an equally useful and affordable solution.
Thanks for bringing this up Willis, this will save many lives if it gets wider adoption and just a small amount of money to educate and set communities up with a cheap ‘starter kit’ of bottles/reflectors.
However, I think this must only be used as a method of last resort, and in no way should it replace schemes designed to provide people with a piped supply of potable water.
Don’t forget that plastic bottles are made to biodegrade much faster today than the older types.
Although it is a simple and easy solution in times of survival, it should not be a long term solution.
As I said, I really doubt that the UV rays are doing anything in the process since they are most likely absorb by the plastic. This could be easily verified and if true they could use glass bottles and reduce their intake of decomposition chemicals and heavy metals.
I too think SODIS is a great idea and have made a donation on their web site to support their efforts. They can use all the help they can get. If you are making a donation they accept VISA and M/C and for VISA at least (I didn’t try using M/C) they use the Verified By VISA process which helps insure a safe payment gateway. When the payment says (the next page after selecting VISA) “Postfinance VISA” it is merely one of their Swiss banking system names for VISA.
Arguing over if any possible BHP contamination as a risk is pointless when you consider the people this is intended to help – the poorest folks on our rich green earth! They would just like to live another day without they or their children falling ill to preventable disease. Let’s work on disseminating this information and assisting in making it the best process possible when the people have no other resources – no money for bleach or iodine as an example – but can use plastic bottles and very simple filters (leave filters in sun to sterilize). Spread the word!
Hi Willis, we have been working with the SODIS idea since 2005 in collaboration with the Luxembourg ILFBV NGO in programs in Africa and South America. It works quite well. And working also on many other simple things for helping kids and the general population in Africa. See our website in French:
http://www.mitosyfraudes.org/Francia/festival.html
and http://www.mitosyfraudes.org/Francia/naguirre_artemisia.html
Procédé SODIS de stérilisation de l’eau
De l’eau contaminée par des bactéries, mise au soleil dans une bouteille en plastique pendant 6 heures devient complètement stérile.
Notre ONG a déjà réalisé des projets pilote dans plusieurs pays : Colombie, Pérou, Malawi, Palestine, Maroc.
***************
And Jimbo: Glass is not so good for SODIS because it filters UV radiation.
@various commenters
Don’t you realize that anything that solves a problem identified by Greens is anathema to Greens.
Overall …… if the choice is between drinking water au naturel and using SODIS …… I know which I’d choose. You?
I remember seeing an invention on the New Inventors (Australian ABC program) in which a chap had designed a plastic panel system with smallish cell-like structures designed to utilise sunlight to evaporate the water as it passed through by gravity. I can’t seem to find it ATM but I am sure I linked it at WUWT in another article some time ago.
This solution is more practical as there is probably no shortage of plastic drinking bottles in less devevloped countries.
I am sick and tired of being scolded for enjoying low-mineral water- the tap water in Mojave is typically 600 ppm total dissolved solids, and tastes like baking soda. I really don’t want kidney stones, either.
A number of folks have commented that the SODIS method won’t kill everything. This is true. But if it can reduce the incidence of third-world childhood diarrhea in a given area by 80% or so, it is a huge win. Heck, if it reduces it by 10% we’re still talking lots and lots of kids.
If things don’t get killed by the standard method, you just need to get the water hotter, which is easily done by a) putting it in a reflector (tin roof pieces, aluminium foil, pieces of tin cans, etc.), or b) half-way bury the bottle on its side in sawdust or hay or leaves etc. to slow heat loss, or c) throw a piece of clear plastic over a row of bottles on the roof and weight the edges to prevent air exchange, or d) all of the above, or e) some other cheap (preferably free) method.
Me and a friend of mine made a preheater for water. We took a 100′ coil of 3/4″ black plastic pipe, plumbed it into the system before the water heater, and threw the coil up on the tin roof. We covered it with thin clear polyethylene sheeting, but in the summer we had to take the clear sheeting off … the water in the pipe was boiling at the peak of the solar day.
These kind of things to me are perfect examples of the “no regrets” plan for dealing with the (likely imaginary) dangers of CO2. The “no regrets” plan is to do things that we will not regret doing even if CO2 is not the global thermostat. Let’s protect people now from the vicissitudes of climate. Then if climate does worsen we’re already ahead of the curve … and if it doesn’t, we’re even better off.
w.
As Ray above pointed out, plastic bottles blocks any disinfecting UV rays. Glass would be better, and not leach any chemicals into the water.
Or is the idea that the heat alone is enough? I do remember from extended hiking trips that the old “boil for 5 minutes” meme is excessive. 60 degC will kill off most bacteria in the natural world, and you might get pretty close to that in a bottle on a tin sheet under the African sun.
Everyone keeps making comments about if this or that is UV transparent.
It very much depends on the specific item. For instance optical glass cut off of UV varies according to its refractive index with high refractive index glass tending to pass less UV than lower refractive index glass. Likewise common glass is more or less transparent to UV depending on the iron content of the glass among other things. Plastics also vary depending on thickness and if they are treated with UV resistant coatings.
This doc shows the results of some testing. It implies that polyethylene has the highest UV transmission so perhaps in an emergency situation a common PE sandwich bag would the the container of choice, or a common PE milk jug.
http://www.sodis.ch/methode/anwendung/factsheets/glass_pet_e.pdf
In time, I know for a fact based on personal experience, that common PE milk jugs will get brittle after prolonged exposure to day time sun.
Heat being the most reliable method, I see no reason that a continuous treatment system could not be developed for a central water supply, using a long length of appropriate tubing and a flow restricter to limit water movement to a drip by drip passage into a collection container.
For a small village or even a family a few feet of tubing, an input container with sand filter, passing into the tubing which is coiled inside a heating chamber heated by a low concentration reflector then a drip restricter into a collection bottle could provide a near continuous supply of water which has been held at sterilization temperatures.
You do not need to boil the water, the sterilization is a combination of temperature and residence time, with 165 deg F (74 deg C) sufficient to kill many common bacteria if held for 15 minutes or so. Higher temperatures allow shorter duration heat exposure (+80° C (176° F) for ten minutes or at +90° C (194° F) for one minute.
Likewise UV sterilization is a combination of the intensity and duration. UV A being the preferred, but other high intensity light frequencies also can cause biological damage disinfection if duration or intensity is high enough.
http://www.ncbi.nlm.nih.gov/pubmed/10169625
I suspect that all of these mechanisms are at work in the real world.
Larry
Not true. See
http://www.sodis.ch/methode/anwendung/factsheets/glass_pet_e.pdf
for a comparison. PET is not as good as glass, but the transmissivity is a hair over 70% vs a hair under 80%.