LE FOYER AMELIORE EN ACTIVITE
The Bangang
As its name indicates, the biogas digester exclusively uses biodegradable materials as fuel. It is a 3-part system that functions automatically and therefore requires almost no manpower.
One of the first things that Mary and I set about doing upon our arrival in Cameroon was to interview people about their water use and sources and to do some water quality testing on those sources.
We bought the water testing kit back in Boston from an MIT professor. It mainly serves to identify whether or not a water sample contains E. coli or other coliform bacteria (coliform is defined “as gram-negative rods which produce acid and gas from lactose during metabolic fermentation”). Part of the sterile water sample is squirted onto a Petri-film on which E. coli will grow blue colonies and other coliform will grow red colonies. Another part of the sample is put in the Colilert tube. If E. coli are present then the sample will turn yellow and fluoresce under UV light. If just coliform are present the sample will still turn yellow but not fluoresce. The results of both the Petri-film and the Colilert tube are evaluated after 24 hours of incubation at body temperature.
We started with the water sources close to home at the ACREST Center. These include the nearby river, named the Mii, the rope pump outside the gate, and water from the rope pump that was then treated by a biosand filter manufactured by ACREST.
The River is used by many for washing and cleaning. Neighboring children come by the rope pump all the time to get water to carry home for cooking, washing, and drinking. The ACREST staff drinks the water from the biosand filter. Below is a picture of Colilert Test and Petrifilm Test results.
Water testing results.
The River is highly contaminated with E. coli and other coliform and is classified as high risk. The water from the well with the rope pump is not quite as dirty but is also classified as high risk because E. coli are present. But the water from the rope pump well treated by the biosand filter shows a dramatic difference. Coliform are present but the there was no E. coli found. The water is designated as low to intermediate risk. The biosand filter had improved the quality of the water and lowered its health risk.
The ACREST staff were trained by a Canadian NGO named Centre for Affordable Water and Sanitation Technology (cawst.org) in May 2008 to manufacture the biosand filter and since has manufactured many filters.
ACREST staff constructing a biosand filter.
A cross-section of the filter is shown below. They are constructed from concrete and other locally-available materials. The filtration is aided by the mechanical trapping by the sand, gravel, and stone and the natural ecology of the micro-organisms that grow in the filter. The filter works to remove parasites, bacteria, organic compounds, and some inorganic compounds to improve the quality of the water.
Taken from Biosand Filter Brochure made by CAWST (cawst.org).
ACREST has not fully begun marketing and disseminating their biosand filter, but we were able to visit the home where the first filter sold had been installed. The family treated all their drinking from their well with the filter and reported that it had improved the health of their family.
The first biosand filter bought from ACREST installed in a home near Bangang market.
Some maintenance and cleaning is required about every six months to keep the filter working properly. The top layer of sand needs to be cleaned and exchanged. Proper training on how to take care of the filter is given when the filter is purchased. On our visit to the compound, Simon showed the family how to maintain their filter.
Simon showing the family how to clean the sand in the filter.
A drawback of the filter is the amount of cement that it requires and the weight of the filter. Mary and I hope to help by slightly redesigning its structure in order to reduce its weight and cost.
Kennedy is currently the person heading up the Jiko project at ACREST. He arrived at ACREST in October of 2008 and started working on the stoves, which are called liners. He has made 98 liners; 12 cracked because of the gauge. He is also heading up the construction of the “better born kiln” (to be written about in another blog entry) for the mass firing of the jikos. They sold the first jikos in February of 2009 and have sold about seventy since. Recently, the main tasks have been collecting clay for the stoves from a riverbank, drying and sifting the clay, constructing the kiln, and production of the stoves. Right now, there are 88 more stoves ready to be burned and 64 ready for the metal cladding.
Tharaquet ceramic Jikos (T.C.J)
In one week, five people can make 100 energy-saving stoves. So in one month, you can get 400 energy saving-stoves, although it depends on weather. You must do your best on mixing and production so that you get 100% quality in all areas.
PROCEDURE
Mary and I are students from MIT who are interning with ACREST for the summer of 2009. Our projects are focusing on water pumping technologies mainly for dry-season farming but since arriving in Bangang we’ve had a wide introduction to the various activities taking place at ACREST.
Part of ACREST’s current focus is on micro- and pico-hydro projects that make use of the flow of the Mii River. They have been through a few generations of the system, and the staff is now working on two generators that will provide 50 kW and 100 kW of power, fondly called “the machines” by the ACREST staff.
On one of the first mornings that Mary and I arrived here, we walked with Arsene and Gilbert along the road following the ACREST-installed electric lines that led us to the micro-hydro project. The first evidence of the micro-hydro project was a low-head dam and diversion that reroutes a portion of the water away from the impending waterfall. The dam and diversion were begun over a year ago, but the wall supporting the diversion collapsed a few months ago due to erosion, but ACREST had recently finished repairing it.
Following the diversion, we were now at the top of sharp steps cut into the clay that led down to the generator house. The steps snake along the same path as the water pipes and the elevation drop provides about 20 m of head to the turbine.
It was an exciting day and most of the staff had gathered at the site because they were testing the 50 kW generator. A group of workers were crowded into the generator house. The signal was given to open the gate to let the water run through and to let the turbine spin.
The turbine kicked into motion and the belt connecting it to the generator vibrated furiously. But soon it was obvious that the turbine could not get up to speed, and the problem was pinpointed by the electrician Momanyi as being a short-circuiting diode in the generator. The test was finished for the day as the diode needed to be repaired.
Later in the week after the diode had been replaced, the 50 kW generator was tested again, but this time it was shown that the flow rate coming in through the four inch diameter pipes was not great enough for this particular generator and that it needed to be downsized and replaced with a 10 kW generator.
A few other problems with leakages in the pipes and in the generator house need to be corrected before the crossflow turbine and 100 kW generator are tested. ACREST describes itself as being in its research phase. It is still testing and prototyping many appropriate technologies and is forming plans for wider dissemination in the future.
The power from these micro- and pico-hydro plants is a key part of their plans for future growth. ACREST would like to generate enough power to expand and run their machine shop to full capacity which will in turn provide a means for the increased production of appropriate technologies for the surrounding area.
ACREST is expanding their micro- and pico-hydro projects and plans to construct their own turbine and generator to be installed at another site along the Mii.
Photos (clockwise from top): Mary climbing the steps that follow the water pipes; Momanyi, an ACREST staff member, walking along the diversion wall; ACREST staff in the generator house testing the diode.
