A Reid Harvey on wed 23 aug 00
Dear Janet, Mel, Paul, Gavin, Louis, Everybody,
For the sake of better understanding I would like to give a somewhat
simplified description of the earthenware water purifiers of both
Potters for Peace and Ceramiques d'Afrique. The two are very different
in design, thus far that of PFP being better established and accepted
than that of Ceramique d'Afrique. More complete descriptions can be
found at the two web sites following, for Potters for Peace:
http://www.cc.cc.ca.us/pfp/Pfpfilter.htm
And for Ceramiques d'Afrique (now relocated to Bangladesh):
http://www.geocities.com/ceramafrique/
The Potters for Peace 'filter bucket,' which they call 'filtron,'
resembles a flower pot, is 6 to 8 liters volume, and gives somewhere
between about 1.0 to 1.5 liters of flow per hour. It nests in a second
container, which catches the purified water. There is a simplified
picture, illustrating the way this filter works toward the beginning of
the filter page, URL given above.
The PFP filter is made by combining equal volumes of moist clay and fine
sawdust (30 mesh?), then forming by either wheel throwing or hand
building. In the last year or so this body has also been pressed, using
a hand operated jack, where a number of people have seen a need for a
more standardized looking filter, i.e.. having uniform thickness, etc.
But for all of the filter buckets, after firing, to ^08 or 010 or so, a
very dilute solution of colloidal silver is painted on. So, disinfection
happens in two ways, firstly by pathogens being filtered out, and
secondly by contact of remaining pathogens with silver, wherever they
have not been filtered out. I still think it quite remarkable that most
lab tests have indicated 100% removal of the pathogens.
The PFP filter is very simple to make, and it is an easy technology for
traditional potters to adapt. In many cases this is a wonderful model,
and there is an urgent need for developers and health and water experts
to become acquainted with this filter for more widespread application.
It meets the three part test for appropriateness and sustainability of,
that is: low cost, easiness of use and effectiveness. And it meets the
further test of being easy to make locally, almost anywhere that the
population is at risk.
As to the Ceramiques d'Afrique filter/ purifier, we started developing
this full time a little less than two years ago, partly because there
was a problem transporting the Potters for Peace purifiers following
hurricane Mitch. In Nicaragua, lots of the roads were in bad shape and
potters appeared to be too spread out to meet the need for the
purifiers. The Ceramiques d'Afrique purifier is in the form of a
'candle,' a small cylinder of 5 to 8cms. diameter, by 10 to 14cms.
height, which fastens into the upper container of a two tiered system,
similar to that promoted by PFP. (The two tiers being an upper container
with bacteria contaminated water and a lower container with purified
water.) The candles small size makes it easy to transport, so it is
suitable, for example, for rapid response to emergency situations, like
hurricanes or floods. It is also appropriate where roads are poor and
potters are few and far between.
For emergency situations, because the purifier candle can be made
locally, the emergency response could be turned into a long term, public
health initiative. But it must be said that when comparing the filter
candle to the filter bucket, the candle is not as easy to make. In order
to get the great improvement in flow (the candle has about ten times the
flow per area of the filter bucket), it is necessary to go through many
steps in all phases of production. Though the clay body consists of red
clay and a combustible only, it is highly processed. (By the way Mel,
there are no secrets whatsoever.) My primary task in researching the
purifier candle was to greatly improve flow, as well as getting control
of the amount of flow.
Bear in mind that I'm still hoping to keep the candles simple, and in my
seventeen years experience in 'third world' countries I firmly believe
the technology is not beyond what can be done in most places, at least
in the larger cities. Following are a list of steps in making dry
pressed, earthenware purifiers. The claybody for pressing consists of:
45% plastic, red clay, 45% porous grog (see below), 10% combustible, in
this case wheat flour at 350 mesh.
1. Prepare to make porous grog material, 63% plastic, red clay (30 mesh)
and 37 % wheat flour. (Note that wheat flour is a pain to work with, but
is used because it does work in achieving good flow and because it is
available almost anywhere in the world. One of the first tasks in a new
project would be to find a substitute with similar, fine grain.) For
making porous grog, think in terms of using no more than 8 to 10% water
content, though using more to begin with, and drying back to the correct
amount.
2. Mix all of the clay with all of the water, plus a little extra water.
So in effect you have a clay water mix with about 35 to 40% water
content. This high amount of water helps in quickly getting the clay
somewhat plastic.
3. After 30 to 60 minutes, mix in all of the flour by hand. Spread the
material out for some drying. Throughout the drying, over perhaps two to
four hours, alternately screen to 10 mesh and mix. This is very labor
intensive, but provides much needed jobs!! Note that we have started
with excess water because this helps facilitate good mixing.
4. When the clay/ flour mix is dried back to about 8 to 10% water
content, bag it. You now have about 24 hours to press this material
before it begins fermenting to high heaven.
5. Using a simple press, made from a car jack (hydraulic, scissors jack,
etc.), press the clay material into disks, say 40mm. diameter by 10mm.
thick. We do our pressing into a piece of PVC pipe. The disks allow
stacking in the kiln and even heating.
6. For firing porous grog disks drying is quick since water content is
low, and even if firing while the disks are damp the water goes off
quickly since the disks have a very open structure. But the flour must
be burned off slowly or bloating and breaking will occur, possibly
negating some of the porosity of the subsequent powder. Go slowly
through the temperature where flour burns off. Be ready for lots of
smoke. Our current grog was fired to ^08, but it should be possible to
fire at lower temperatures.
7. The porous grog can be easily crushed in a wooden mortar. It should
be screened to 30 mesh.
8. Using a scale, combine dry pressed materials at 45% plastic, red
clay, 45% porous grog, and 10% flour. Water content should be measured
at 10 to 12%, where this will dry off to 8 to 10% during the process of
pressing. Note that for mixing the dry press materials, there are no
special steps, as is the case with the grog.
9. Now it is time to press the purifiers. To see pictures of this, I
suggest having a look at the home page of Ceramiques d'Afrique, URL
above, and once there clicking onto the link to the tour of the
production line, shown at the page header. The second of the four links
within the tour shows the dies used and the press. Basically there are
eight dies that form a kind of wheel. The center void of these is
charged with the clay powder and eight bolts around the outside of the
die set are tightened in order to do the pressing. A further step in
pressing forms the closed end of the purifier.
10. Brush on a dilute mix of either colloidal silver or silver nitrate.
If silver nitrate is used a further firing is necessary, in order to
burn off the nitrate in reduction. Colloidal silver is easier to use,
though not available nearly so widely as the silver nitrate. The few
times I've used the colloid I have obtained this from Potters for Peace.
It has a concentration of 0.32% solution, and PFP gets it from a Mexican
company called Microdyn.
11. Fire the purifier candles to ^08. I believe the filters can be fired
at much lower temperature, but this will alter the amount of flow, to an
amount I cannot yet predict. Firing to ^08 will give purifiers that
average about 1.0 liter per hour of flow.
One further process necessary in making the purifier candles involves
the making of the dies, as well as master molds. The entire mold and die
system is shown in the third link of the production line tour. It may
look daunting, especially for those to whom work with plaster is not a
favorite aspect of ceramics. But I believe those with some knowledge of
model and mold work would find the system very simple. With a
specialization in plaster techniques myself, I believe that it should be
possible to make millions of purifier candles, starting from a single
model and block mold, the basis of the system shown.
I would like to address the concerns of Louis Katz with respect to the
inappropriateness of various projects and products, foisted onto 'third
world' recipients by foreign donors. Louis has an excellent point when
he describes the absurdity of: the use of $3000 oil burners for use in
wood kilns, or the building of electric wheels that don't allow the
villages to use their highly
developed coil throwing skills. The pity of this approach to development
is that it is not only foreign donors pushing these ridiculous projects,
but the host country leaders themselves. Time and again I've seen
appropriate projects shot down by host country leaders, simply because
they want to be 'modern' or in every way western. As to water purifiers,
for example, I would imagine that many host country leaders would say,
"why are you telling us to purifier water this way, when you are not
promoting this technology at home?" These kinds of leaders are some of
the many who feel that the job of developing their countries is
primarily that of foreign donors.
At the moment there is a further problem that I personally am having.
Now that I have described the way of making purifier candles I am
conscious that it is quite complicated by comparison to the Potters for
Peace filter bucket. I would hasten to say, however, that I think it is
important not to confuse what is complicated with what is appropriate.
The most recent purifiers we have made were put together entirely by
local people in the Ivory Coast, following the steps above. The only
steps in which they were not involved were those concerning model and
mold making, parts I did myself. However, model and mold making steps
are also quite do-able, especially since master molds are have been
made.
Sorry for so long an explanation, due almost entirely to the many steps
of purifier candles. For Gavin and others who would like to help spread
the word I would suggest starting with the making of filter buckets, the
purifiers promoted by Potters for Peace. These are very easy to make and
to understand.
I close for now, but would be happy for any observations or questions. I
have written this hastily. Please forgive any omission.
Regards to all,
Reid Harvey
Autumn Downey on wed 23 aug 00
Thank you for your explanation of the filtering system, Reid. The websites
are very informative.
Is there a lifespan to either the candles or the bucket style filters? Do
they have to be recoated with colloidal silver after a certain amount of
use?
Good water is becoming a concern in the west too - which may help the cause
in other parts of the world.
Autumn Downey
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