Alow-tech water filter made from a plastic rubbish tin and a clay pot, which produces
safe drinking water from dirty ponds and wells, is having a dramatic impact on poor
rural households in Cambodia.
Painting filter surfaces with anti-bacterial colloidal silver.
The device removes microbiological contamination at the point of use. This reduces
diarrhea, eliminates the need to boil water, reduces work and school time lost through
illness, and saves money on water purchases, firewood and medicines.
The filter elements are made and assembled by women potters and an estimated 20,000
filters will be distributed this year.
The ceramic water purifier (CWP) was originally developed in Central America by an
NGO called Potters for Peace.
The idea was brought to Cambodia by International Development Enterprises, a non-profit
NGO with a mission of reducing rural poverty through market-based affordable technologies
and micro-enterprise development.
IDE - funded by the Canadian International Development Agency - assisted a women's
pottery co-operative in Kampong Chhnang to start making the filters in August 2000.
The Kampong Chhnang factory produces 2,000 filters a month as a commercial enterprise.
They sell for $7.50 each. The main buyers so far have been NGO and donor agencies,
but IDE is now helping to establish a distribution network and promotional campaign
to sell filters to households.
A second factory has recently been started in Kandal by Resource Development International,
another NGO, and a third is being built this year in Prey Veng province with funding
from the World Bank and implementation by the American and Cambodian Red Cross, and
Assembled filter units, at right, being flow-tested before distribution, at the Kampong Chhnang pottery factory.
IDE country director Mike Roberts expects 20,000 filters will be distributed or sold
this year, in Kampong Chhnang, Pursat, Kampong Cham and Prey Veng.
A year-long study of filters in use in 1,000 rural households showed they were effective
in producing clean water from various untreated sources. The filter element is a
porous pot made of kiln-fired clay, impregnated with colloidal silver, an anti-bacterial
agent that was used extensively in medical practice prior to the development of antibiotics
in the 1940s and 1950s. The clay eliminates most water-borne pathogens (such as E
coli, cryptosporidium, and giardia) but lab tests found that the colloidal silver
was needed to achieve complete disinfection.
The silver coating will last at least several years before losing effectiveness,
according to Roberts. "Decreasing flow rate due to progressive deep clogging
of the pores may be the limiting factor to the CWP lifespan but this must be confirmed
by further testing." He notes that filter elements can be replaced at relatively
low cost (currently $4.50).
In household use the CWPs produced water meeting WHO low-risk guidelines or better
(10 or fewer E coli per 100 ml), regardless of the input water quality (rivers, lakes,
tube wells, lined and unlined open wells, ponds, rainwater).
The clay pot filters are shaped in an aluminum mold and the surfaces scraped smooth before firing.
Sixty-nine percent of households boiled their drinking water "always" or
"sometimes", and almost all stopped boiling after using the CWP. Most water-boilers
saved 22 hours a month in time spent gathering firewood.
Households that did not boil water prior to the CWP showed significantly less diarrhea
incidence: when compared to non-boiling, non-CWP using households, CWP users had
17 percent more households reporting no diarrhea in the past month, about half as
many cases per person, about one-third of the medical treatment costs per person,
and about four times fewer work/school days missed per person.
The clay element is set in a plastic receptacle fitted with a plastic lid and metal
spigot. The element holds 10 litres which seeps through at the rate of 2-to-3 litres
an hour, allowing a production of up to 20-to-30 litres a day.
Users are asked to scrub the filter element monthly to clear clogged pores, and wash
the tank with soapy water to prevent bacterial growth; originally the recommendation
was twice a week, and it is believed this frequency contributed to the rate of filter
breakages. The clay filter is the most fragile part of the device and over a nine-month
period, for every 1,000 in use, an average of six were being broken every month.
In a separate project, 4,200 CWPs were transported to four northeastern provinces,
averaging 300km by boat and 300km by truck. Fifteen filters were broken, mostly during
loading and unloading.
There was also a problem of abandonment of use. In two villages supplied it was found
that 40 out of 101 households surveyed had stopped using their CWPs regularly: five
said they used it sometimes, 35 said they never used it. Most of the larger group
were found to have stopped use when the (then plastic) spigot broke, or the filter
element was broken.
IDE says these problems have been overcome by the use of a steel spigot, less frequent
filter cleaning and more care during transport. Mike Roberts also believes breakage
and/or abandonment will be less common among households who buy CWPs with their own