I too appreciate biosand filters, with their bacteria colonies building gels that filter out other microbes.
Legionella bacteria makes up a "significant proportion" of the bacteria in slow-sand filters. Hurray for Legionella. So badly demonized, increasing the sales of antibiotics for water systems in the industrialized countries.
Thanks Herb. The biosand filter is an excellent low cost and appropriate technology. see http://www.howard.edu/kenya for work some of our howard engineers without borders students did in a rural community in wesern kenya. the team went back last year and installed another eleven filters. when we went back, we visited an orphan house where the team had installed a biosand filter the previous trip. the orphan house "mom" told us she hadn't had a single case of water borne stomach ailments in her 20 orphans since we put in the biosand filter and trained her to operate and maintain it.
On Thu, May 8, 2014 at 8:28 PM, herb fox <[log in to unmask]> wrote:
I read the post and ancillary material before Sam posted it and rejected it for other reasons than those raised in the posts.
I found the whole approach paternalistic and disrespectful of those it intended to help. Advanced technology requiring 1st world production techniques is not the way of Science for the People. SftP should be of, by, and for the People. As much as possible it should be based on the traditions of the people, be producible by them and use indigenous materials. The issue of potable water is central to improving and extending the lives of people throughout the world, in Haiti also for example. There a colleague, Bob Giles, with a long experience in Haiti and adequate command of the language worked with some young Haitians and USA university students to resurrect a device that could be made entirely with indigenous materials, require existing native skills, and be understood by those who would be using it.
The bio-sand filter is a slow filtration system that uses a casing made from cement and filled with three different layers of sand. The system purifies water in four basic steps: mechanical trapping (suspended solids and pathogens are physically trapped), predation (pathogens are consumed by other microorganisms), adsorption (pathogens become attached to other suspended solids in water and the sand grains) and natural death (pathogens finish their life cycle or die because of oxygen and/or food starvation).
“Another key aspect of the bio-sand filter is the bio-layer,” she notes. “This layer removes up to 70 percent of pathogens through mechanical trapping and predation.”
During Giles’s visit to Haiti last summer, he and his HDSC staff hired workers to build the filters and conducted a teachers’ science training program for select graduates of College St. Jean in Les Cayes.
“The young adults in the training program were taught how to test water and develop technical reports detailing water quality before and after filtration,” he says. “They will be responsible for installing five filtration systems within the community.
Those of you who have read Cliff Conner's book know, as one reviewer put it the triumphs of science rest on a "massive foundation created by humble laborers," he writes. "If science is understood in the fundamental sense of knowledge of nature, it should not be surprising to find that it originated with the people closest to nature: hunter-gatherers, peasant farmers, sailors, miners, blacksmiths, folk healers and others."
Let those who believe in Science for the People and have been privileged to become knowledgeable in a science do their utmost to respect the people they would help by making them integral to the process of defining problems and participating from the beginning in obtaining solutions that rely as much as possible on their traditions, materials, and processes of doing and thinking. PhDs might be amazed at how much can be learned from the people they want to help.