[Stoves] A simple water sterilization technique

Fri Feb 15 21:22:57 CST 2013

Bruce,
The wax is "Myverol 18-06 K" from
http://www.integratedsolarcooking.com/makewapis  This website also had the
other parts list,  instructions for construction and contact info near
bottom of webpage.
Kind regards,
Jeff

On Fri, Feb 15, 2013 at 2:00 PM, Bruce Stahlberg <
bruce at affordableenergysolutions.com> wrote:

> 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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