Re: sterilising drinking water

["Kevin Chisholm" <kchishol@fox.nstn.ca>]

Dear Dr. Karve

 

The concept of a silver spiral in water to sterilize it is interesting. I am curious as to mechanism involved in sterilizing water. Has the Dept. of Science and Technology been able to hypothesize a credible mechanism?

 

Kindest regards,

 

Kevin Chisholm

----- Original Message -----

From: A.D. Karve

To: Reedtb2@cs.com

Cc: stoves@crest.org

Sent: Saturday, January 26, 2002 6:40 AM

Subject: Re: sterilising drinking water

Water used to be stored in my childhood days in copper vessels, because the copper ions that entered the water had a germicidal effect.  However it was later shown that the copper also caused liver and brain damage among some infants. (I must have been among the lucky infants that were not harmed). It did not harm adults. The richer families in India stored water in silver vessels for the same reason. No physical harm was ever reported in families that used silver vessels. The Indian Institute of Science, Bangalore, India, developed a spiral of silver.  This spiral, suspended for 12 hours in a pot filled with water, killed all the bacteria in it.  An analysis of the water with even the most sensitive instruments failed to show the presence of silver ions in the water.  The method has now been recommended by the Department of Science and Technology, Government of India. It is a very cheap method, but unfortunately it has not been widely publicised.

A.D.Karve

-----Original Message-----
From: Reedtb2@cs.com <Reedtb2@cs.com>
To: adkarve@pn2.vsnl.net.in <adkarve@pn2.vsnl.net.in>; crispin@newdawn.sz <crispin@newdawn.sz>
Cc: stoves@crest.org <stoves@crest.org>
Date: Monday, January 21, 2002 7:09 AM
Subject: Re: Practical boiling

Dear Karve, Crispin, Stovelist and Gasification list:

I dream of making significant improvements in cooking during my lifetime, but have added CLEAN WATER to my list of problems because it fits so close to stove making and gasification.  However, I am horrified at the idea of boiling all drinking water.  What an enormous energy and time expense.

It seems to me that CLEAN WATER could be an easy add-on to gasification.  Clean water can be achieved at village scale with activated charcoal and electric power.

Maybe there is a simple chlorinator that could make the chlorine for a local water supply.  However, oxygen is favored today over chlorine for pathogen treatment and a simple ozonizer would achieve the same results - with 1 kW power maybe.

The downdraft gasifiers we make for electric power (15 kW at CPC) typically produce 5 to 10% of a black "char-ash" that has been to 700 C and above.  While not enough for GOOD activation (giving an iodine number of >1,000) it does give activated charcoal (IN >300).  If necessary I believe a VERY simple activator could be added to the outlet of the gasifier to achieve higher activation.

I hope someone with a bad water supply will grab this idea and demonstrate it.  Talk is cheap.

Your truly,      TOM REED     
In a message dated 1/12/02 9:42:18 PM Mountain Standard Time, adkarve@pn2.vsnl.net.in writes:

 A few years ago we were approached by a voluntary agency working on rural
health problems to modify the design of our unbaked mud stove by adding a
cylindrical vertical cavity near the point of attachment of the chimney.  In
those days, a variety of liquids, that are now being sold in plastic
bottles, used to be sold in India in glass bottles of about 750 ml capacity.
Therefore these bottles were quite common in Indian households, even in the
rural areas. The cavity mentioned above was designed for accommodating such
a bottle filled with water. This water used to attain a temperature of about
80 degrees centigrade during the process of cooking.  The medical experts of
this voluntary agency told us that water could be sterilised by heating it
upto about 80 degrees and by keeping it at that temperature for some time.
This objective was achieved by the simple modification to our stove model.
This voluntary agency wanted to popularise this stove design with a view to
providing babies with sterile drinking water in order to avoid waterborne
diseases among infants. Later they told us that the incidence of waterborne
diseases among infants was dramatically reduced in those households that
adopted this stove.
However, this anecdote must be followed by another.  In Pune, the tap water
supplied to the city is filtered and chlorinated, but many householders,
including my own, have their own doubts about the integrity of the water
purification system, and therefore, they subject the drinking water to
further treatment. The University of Pune conducted a survey in which
householders in Pune city were asked if they drank tap water directly or if
they subjected the water to any further treatment before drinking it. The
second question was about the frequency of diarrhoeal attacks suffered by
members of the household during the previous year.  The results of this
survey showed that the persons who drank tap water directly suffered the
least from upset stomachs while the households that boiled their water
showed the highest frequency of such diseases.  Those who used various
filtering devices fell between the two groups. This showed that challenging
the body with small doses of pathogenic bacteria was necessary to keep the
immune system alert.
A.D.Karve