Ceramic Pot Filters treat water borne disease.
By Burt Cohen
Potters Without Borders originally met with students and Professor Streibig at Seattle University. As a result of this meeting I was asked to assist with the introduction of a Ceramic Water Filter facility at the Songhai Centre in Porto Novo Benin. I traveled to Benin and worked at Songhai centre from August 8th until September 12th, 2007. My participation was a result of a grant provided through the Rotary club of Spokane.
More then two months before arriving both Professor Streibig and myself communicated with Project Coordinator Thierry Andre and Songhai Centre Director Godfrey Nzamujo to identify materials and facilities needed for the production of Ceramic Water Filters. A week before my arrival, Engineering and nursing students and programme coordinators from Gonzaga University traveled to Benin.
The introduction of a new technology brings with it new challenges. The Songhai Centre in Benin has more then a twenty year history in Benin developing an integrated programme of agriculture production and community development in West Africa. This model is an excellent basis for the development of a ceramic water filter facility with an excellent potential for success. The centre views the introduction of this technology as needed and timely. Songhai is uniquely situated with a local market in Benin as well as a potential market in Nigeria of many millions less the 40 kilometers away. The integrated nature of the Songhai model influences their view of future CWF production.. In discussions with Thierry Andre, project coordinator and centre director Fr. Nzamujo it is hoped that CWF production can be introduced along with the development of other ceramic production including, brick, tile, ceramic planters and irrigation pots.
Upon my arrival in Benin, the students from Gonzaga and the Songhai Centre mechanics team had organized clay processing. The engineering students had developed an excellent portable filter press and had already formed 25 filters. This press- allowed us to form over 120 filters for the batch series test in order to evaluate the proper ratio of clay to sawdust.
Gonzaga University Portable Filter Press in Operation
Double scissor Filter Press
The last two weeks of my stay I worked with Mr Fiacre Aboua, Mr. Eusebe and Mr. Luciane of the mechanics workshop at Songhai centre to produce a new double scissor filter press. This press was tested during the last days of my stay to make sure that it was aligned. Some small adjustments needed to be made so that the filters would eject filters easily.
Forming Ceramic Water Filters
Based on evaluation of the flow testing results, I recommend that a ratio of 80% clay to 20% screened sawdust be used. For more information including formula see: benin-ceramic-water-filter-batch-series.doc
When the new filter factory begins to form new filters there will be some changes. It is important that all new filters be numbered in such a way that filters can be monitored. Each filter must receive a unique number as soon as it is formed .This numbering is stamped into the newly formed filter before it is ejected from the mold. The factory must keep daily reports to record all information about filter production. It is important that information about filter production indicate the number, the date of production, clay and sawdust proportions, weight of water, firing information and any unique information pertaining to production. A sample workshop log is provided as an example- benin-production-log.xls
Once filters are sold the sales information must also indicate the Filter number sold to a customer as well as the customer’s name and home address or village. This information is necessary to follow up studies that will monitor the filters’ effectiveness in the field.
Kiln Construction and Operation
The kiln built during the period of the consultancy was meant to be one of two “Mani” type kilns. The first kiln has a double firebox design under the floor of the kiln. The kiln will fire more then 50 filters.
Kiln firings take 11 to 12 hours because of the warm up period needed to insure that carbon does not become trapped in the filter walls. A firing schedule has been included.
I recommend the use of draw trials to help with the evaluation of the firing progress. These small trials are made of the filter clay/sawdust mixture and removed at the end of the fire through a spy hole in the door od the kiln.
Pyrometric cones * are also used to make sure the fire has advanced correctly. Ordering information for these cones is included.
This kiln was made from red brick made by Jean Kokossou of Porto Novo. This brick was delivered in three lots. The first batch of brick was not fired hot enough to be durable. The next batches were fired higher and were stronger. The kiln was fired twice while I was in Benin. After the first firing the flat top cracked and separated from the wall. Before the second firing we rebuilt the roof as an arch.
I would recommend that the next kiln be built with an arched roof as well and that the second kiln share the chimney with the first.
The first kiln made use of 100 fire brick to cover the fireboxes and form the floor of the kiln. The use of firebrick was important as waste oil is a stress on the red brick used in the fireboxes. If possible firebrick should be used in the base of the second kiln. If it is not possible to buy firebrick for a second kiln, then I would suggest that outer walls of the next kiln be made twice as thick. If firebrick is found, then the fireboxes and floor of the kiln can be made from this brick and the chamber can be red brick.
The most important problem with firing filters at the Songhai Centre is the fuel used to fire the filters. Although we used waste (black) oil to finish both filter firings, waste oil is not a recommended fuel in this kiln because of the poor quality of the brick. The brick in the fireboxes will darken, vitrify and deteriorate with the higher temperatures from long use of waste oil.
Wood used in the firings must be purchased and stored at least three months in advance and it must be split in small cross sections. Unless the wood is completely dry, the firing will stall in temperature beyond 700 C. The difference between using wood in cooking fires and using in a kiln is that poorly dried wood can be used without problem in a cooking fire- in a kiln the same wood will prevent the advance of the firing because the energy of the burning wood is consumed in boiling off the water in the fireboxes. If the wood is completely dry waste oil will not be needed to bring the temperature to 900 C, or very little will be needed.
Other fuels may be used in the kiln-along with the wood such as palm oil kernels (rancid), and agricultural waste such as ground nut shells.
Target filter firing schedule is reproduced in the document: benin-filter-target-firing-schedule.xls
Firing Schedules from the first two firing are shown in the two excel documents: benin-filter-firing-september-6th-2007.xls, benin-filter-firing-sept-10-2007.xls
Follow-up:It would be very useful if the workers responsible for filter firing and production have the opportunity to visit the Ghana filter factory- to participate in firing and production exercises.
Requirements in order to produce bricks for CWF production will be forwarded to the Songhai Centre.
New Filter Workshop
The new filter workshop is developing around the filter kiln. A roof has been built over the new production area. This space is already separated into work areas with cement block walls. Two smaller rooms with doors will provide secure storage for the working solution of colloidal silver, scales, pyrometers and production supplies.
Areas are needed for:
1.dry storage of wood, clay and sawdust.
2.hammer milling of clay
3.screening of clay and sawdust
4.The masons have already provided a soaking tank for flow testing of filters
5.wet mixing of clay/sawdust
6.filter press forming
7.drying racks for finished filters
8.storage of plastic bucket receptacles
10.storage of finished filters
Colloidal Silver ordering information:
Sales Assistant/ Managing Director
Laboratorios Argenol S.L.
Autovía de Logroño Km 7,400
50011 Zaragoza, Spain
Tel: + 34 976 336266
Fax: + 34 976 533659
*Pyrometeric Cones purchase information: 010, 012, and 014
Axner and Company of Florida
Pyrometers and Thermocouples: http://www.wardburner.com/home.html
Director Potters Without Borders
PO Box 1006
Enderby, BC V0E1V0
This Document is also available as a PDF: songhai-pwb-final-report.pdf
Supporting files: songhai-report-documents.zip