[Stoves] Water Disinfection - Mix Boiling Water and Unheated Water to Pasteurize

[Crispin Pemberton-Pigott]

Dear Kevin

This suggestion comes from my work in rural water supply in Swaziland. With 4 others we set up a national water supply branch of the Water and Sewerage Board with WUSC and ODA (UK).

One of the problems in the Swazi lowveld is bilharzia which is contracted by drinking or swimming in infected waters. It is spread by snails and peeing into a water source.

The very simplest method of reducing the contamination burden in water is to store it for three days in the dark.  The main purpose was to implement, quickly, something that would reduce the transmission and reinfection. The solution turned out to be good at killing all sorts of things that depend on sunlight.

For this reason, the systems we were building were created to have >3 days storage, and to be covered completely. As long as the water took three days to get through the system, it would be “improved” in the absence of other treatments.

I have never seen a systematic study of the relative merits of these approaches on real water samples.  In a rural situation where the families are stable, it is best to use slow sand filters with precautionary chlorine or iodine.  This requires good management which means good training of two or three specialists who will take care of the filters. It’s a pretty lazy job, but systematic.

Rapid sand filters require power to run as a system.  If power is available, ultraviolet light is pretty good. I do not know what effect that has on spores, and at what temperature that happens.

The silvered porous clay pots are very effective.  There is a similar (in appearance) system invented by a Canadian for removing arsenic from water in Bangladesh.  Very effective and low cost.

It’s a big subject.
Regards
Crispin


From: Stoves <stoves-bounces at lists.bioenergylists.org> On Behalf Of K McLean
Sent: Monday, September 23, 2019 1:06 PM
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] Water Disinfection - Mix Boiling Water and Unheated Water to Pasteurize

Hi Crispin,

You said "keep [water] in a storage system that excludes all light. Nearly everything dies (but not all, of course)"  I cannot find any research on this.  Do you happen to have any?  This could be a method to disinfect without cost..  Seems like well water should be disinfected, though.

Kevin

[https://ipmcdn.avast.com/images/icons/icon-envelope-tick-round-orange-animated-no-repeat-v1.gif]<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.avast.com%2Fsig-email%3Futm_medium%3Demail%26utm_source%3Dlink%26utm_campaign%3Dsig-email%26utm_content%3Dwebmail%26utm_term%3Dicon&data=02%7C01%7C%7C67a44229c8354a2277ff08d740489b64%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637048552894389918&sdata=eEFzaFTIipsT3%2F%2FSCdG3aaxvfwJ%2Ff27xEC7j08FibW0%3D&reserved=0>
Virus-free. www.avast.com<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.avast.com%2Fsig-email%3Futm_medium%3Demail%26utm_source%3Dlink%26utm_campaign%3Dsig-email%26utm_content%3Dwebmail%26utm_term%3Dlink&data=02%7C01%7C%7C67a44229c8354a2277ff08d740489b64%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637048552894399929&sdata=ZcMq%2BKYUMEdlcoZBC37o2SSheoztJmdyfCvBMqoEMIo%3D&reserved=0>

On Mon, Sep 23, 2019 at 10:40 AM Crispin Pemberton-Pigott <crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:
Dear Andrew

The most important question is what do those temps kill: everything that is bacterial.

Spores are a serious problem and prions even worse. Tough little things. They are not really alive and some coat themselves when “challenged”.

>>Low cost WAPI's wax indicators can tell you 70C is achieved visually

>Thanks for that Tony, I too find this interesting and having a means of indicating the certainty of adequate treatment  would reassure me, who drinks, bathes and cleans with water supplied by a pipe with guaranteed levels of hygiene.

There is a long-standing programme to promote the distribution of those devices in low water quality areas.

>We had a  potter who used to contribute, now deceased , his name escapes me, who made pottery filter jugs which he precipitated a thin late of silver in as a bactericide

Those work very well and remove the need to boil.  Also a slow sand filter (properly managed which means having two in parallel) so, ditto. We always added chlorine as a precaution, with 2 ppm of free Cl at the end of the longest line at the last tap. That takes care of pipeline contamination.

Caution for those planning to test the bacteria after any processing – read how to do this sampling well. You have to “flame” all the containers and the tap before taking the sample. Contamination is very easy. I would not believe a positive result collected by an untrained staffer.

>Interesting chart Crispin but it doesn't show what each of those treatments achieve, or do they all do the same thing to all microbes?

All microbes usually found in water.  Surely there are exceptional cases? Deep sea critters? More escapes heat than I assumed.  It helps to know what is in the water before starting to test a treatment regimen.

>What temperature does kill anthrax, tetanus and botul;sm spores?

Looks like 150 C.  They are no so much killed as destroyed. I think they are not alive in the first place.  “Life” has a loose definition.  A great many water-borne pathogens are killed simply by being in a fully darkened tank for three days. If you have no treatment available at all for washing water, keep it in a storage system that excludes all light. Nearly everything dies (but not all, of course).  Such simple treatment will kill bilharzia, for example.

Drink safe…
Crispin
Ex-Clerk of Works, Rural Water Supply Program, Hhohho District, later Lubombo District, in (then) Swaziland – one of the lighter squares on the board of my chequered career
_______________________________________________
Stoves mailing list

to Send a Message to the list, use the email address
stoves at lists.bioenergylists.org<mailto:stoves at lists.bioenergylists.org>

to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org<https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.bioenergylists.org%2Fmailman%2Flistinfo%2Fstoves_lists.bioenergylists.org&data=02%7C01%7C%7C67a44229c8354a2277ff08d740489b64%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637048552894409934&sdata=xVzSniqhCTt64b7zgvzmkyuXPL1yblKLUMXgCd4juP0%3D&reserved=0>

for more Biomass Cooking Stoves,  News and Information see our web site:
http://stoves.bioenergylists.org/<https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fstoves.bioenergylists.org%2F&data=02%7C01%7C%7C67a44229c8354a2277ff08d740489b64%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637048552894419945&sdata=vTk2fvMic%2BUr3sxFHyv4sSZvUmnIBYWKFfoDbhfP45g%3D&reserved=0>

[https://ipmcdn.avast.com/images/icons/icon-envelope-tick-round-orange-animated-no-repeat-v1.gif]<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.avast.com%2Fsig-email%3Futm_medium%3Demail%26utm_source%3Dlink%26utm_campaign%3Dsig-email%26utm_content%3Dwebmail%26utm_term%3Dicon&data=02%7C01%7C%7C67a44229c8354a2277ff08d740489b64%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637048552894429950&sdata=HNSXY7M5eSS4aMRp%2F1n8FlkSSuTZhXDwfc3HWsrG57w%3D&reserved=0>
Virus-free. www.avast.com<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.avast.com%2Fsig-email%3Futm_medium%3Demail%26utm_source%3Dlink%26utm_campaign%3Dsig-email%26utm_content%3Dwebmail%26utm_term%3Dlink&data=02%7C01%7C%7C67a44229c8354a2277ff08d740489b64%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637048552894429950&sdata=MoHBEzKQs4qjVIDM9hKvpmqn7sPo5QfY8xnzSYk3G5g%3D&reserved=0>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20190923/5c794c0f/attachment.html>