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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
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
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