[Stoves] A simple water sterilization technique

Bruce Stahlberg bruce at affordableenergysolutions.com
Fri Feb 15 16:00:41 CST 2013


Thanks Tom for the information.  Do you know the wax that is used in a
WAPI?  Is it easily, readily available in other countries?  Any other wax
that also melts at or just above the same temperature?

I believe SCI, like many organizations, uses the costs to the general
public of the USA to help subsidize their programs internationally.  Fairly
common practice and seems appropriate.  At $7 - 9 per WAPI, the average
citizen that wants one is not as likely to make one. The additional cost is
for convenience and to help with programs to provide clean water, clean
cooking.

Can you check with Bob to see what materials he uses?  Might be useful for
others on this list to be able to make them locally too.

Bruce

On Thu, Feb 14, 2013 at 6:45 PM, Tom Carter <tom at aguapuraparaelpueblo.org>wrote:

> All-
> No, No, No!  Storing water in a dark container does NOT kill pathogenic
> bacteria or other organisms!  Nor does refrigeration or even freezing.   E
> Coli and other bacteria can survive for weeks in a cold dark environment.
> Heating, filtration, UV disinfection and chemical treatment (chlorine or
> other) are the only recommended methods I'm aware of for drinking water
> decontamination.
> Bacteria tend to cling to particles in the water so allowing it to settle
> or adding a flocculating agent can sometimes help a little.  Particulate
> material in the water also blocks UV penetration and thus makes solar (UV)
> disinfection less effective.
> Part of the problem with bore wells and similar systems is that they
> become readily contaminated by misuse and need to be monitored.  I'm aware
> of a diarrheal outbreak in Kenya caused by a contaminated well, and so we
> recommend frequent testing of community water sources.  We supply the
> testing materials to trained health workers and others at no cost so that
> they can safely and accurately monitor  local water supplies.  For the
> average family it's better to just assume contamination and develop the
> habits of drinking water purification.
> The WAPI's (Water Pasteurization Indicator's) that Jeff Holiman and others
> mentioned cost $7.00 each on the Solar Cookers International website, but
> really only cost about $.05 to manufacture.  Where the rest of the money
> goes, I know not.  Bob Tait of Clackamas, Oregon makes and distributes
> thousands of them for free to various missionary groups and other
> non-profits.  My only point with Bob is that I believe they should used as
> part of a general  program that supports various health and sanitation
> practices including safe latrines, hand washing and clean water storage.
> These practices can be adapted to local cultural practices and should
> include follow up and support.
> Our free training programs include teaching accurate testing and
> interpretation of water samples using the 3M petrifilm methods and a second
> fluorescent confirmatory assay called Colilert. We also train participants
> in the use of the WAPI's, and other disinfection methods and in the
> construction of simple solar and biomass stoves that that families can use
> to heat their water and to cook. The workshops usually take a day and a
> half but for efficiency sometimes can be squeezed into a day.  If there is
> enough interest I could organize one here in Portland or in some other site.
> Tom Carter
>
>
>
>   ------------------------------
> *From:* Crispin Pemberton-Pigott <crispinpigott at gmail.com>
> *To:* 'Tom Carter' <tom at aguapuraparaelpueblo.org>; 'Discussion of biomass
> cooking stoves' <stoves at lists.bioenergylists.org>
> *Sent:* Thursday, February 14, 2013 11:59 AM
> *Subject:* RE: [Stoves] A simple water sterilization technique
>
> Dear Friends
>
> Keeping water in the total dark for 3 days kills quite a lot of things
> including Bilharzia. When I worked in Rural Water Supply in Swaziland we
> provided covered tanks with more than 3 days storage on most systems for
> this reason (in the lowveld). We also used dosing boreholes with
> chlorination occasionally (always when new) and precautionary chlorination
> using bypass jets on pumped systems to get a 2 ppm level at the last
> standpipe. No one boiled water to purify it in those days.
>
> In contrast, nearly everyone in peri-urban and rural Indonesia boils their
> drinking water. Completely different situation, for which stoves are
> required.
>
> Regards
> Crispin
>
>
> Jeff-
> Thanks for the post.  Yes, it's true that pasteurization at 65C kills all
> pathogenic bacteria and viruses, as well as worms and cysts.  I don't
> recommend "feeling it with your hand" however as even a 10 degree lower
> temperature will have a much lower effectiveness.  As you note, a wax
> indicator developed by Dr. Robert Metcalf accurately and safely
> demonstrates when the water is pathogen free.  We distribute them at no
> cost to families and instruct them on their use.  Filtration through a
> clean cloth probably helps a little, as does letting the water settle, but
> is not necessary for pasteurization.  Some methods that use solar UV
> disinfection do require clean water and clear PET water bottles for
> effectiveness.  They also take longer, lack an end point and have
> inconsistent results and for that reason we don't recommend them.
> The last step is keeping safe water safe, by storing it in clean
> containers with small openings so that people cannot recontaminate it by
> dipping in with dirty containers or hands.
> I'm going to give a water testing and water pasteurization workshop here
> in Portland in the next months if anyone is interested in being trained.
> Tom Carter
> Agua Pura Para El Pueblo<http://us-mg4.mail.yahoo.com/neo/aguapuraparaelpueblo.org>
>
>
>
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-- 
Bruce Stahlberg
Affordable Energy Solutions, Inc.
3535 East Lake Street
Minneapolis, MN  55406
612.724.8977
www.affordableenergysolutions.com
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