Somewhere online there is, or used to be, a detailed description of how the WAPI is made by one of the organizations, including the specification of the wax. I believe they did a package with the materials to make hundreds of them, for something like US$80 (several years ago).
I don't have time to search for it right now but it shouldn't be hard to find. On a larger scale, there are also throughflow solar water pasteurizers using a thermostatic valve as the temperature control device. Robert Taylor ----- Original Message ----- From: Bruce Stahlberg To: Tom Carter ; Discussion of biomass cooking stoves Sent: Saturday, February 16, 2013 6:00 AM Subject: Re: [Stoves] A simple water sterilization technique 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 <[email protected]> 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 <[email protected]> To: 'Tom Carter' <[email protected]>; 'Discussion of biomass cooking stoves' <[email protected]> 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 _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/ -- Bruce Stahlberg Affordable Energy Solutions, Inc. 3535 East Lake Street Minneapolis, MN 55406 612.724.8977 www.affordableenergysolutions.com ------------------------------------------------------------------------------ _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/
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