After a slow cooling process of 10-12 hours, the filters are
immersed in a low concentration of colloidal silver solution.
This is an anti-bacterial agent that was used extensively in
medical practice prior to the development of antibiotics in the
1940s and 50s. The amount of silver leached from the CWF
to the filtered water is negligible (far below WHO guidelines
for silver concentration in drinking water) and therefore has
no effect on users' health. Colloidal silver provides a second
level of protection.
Quality assurance is emphasized throughout the
manufacturing and sales process. These procedures range
from the selection of clay and rice husks to flow rate testing,
as well as the breaking and inspection of selected pots to
assure complete kiln firing. Detailed factory records of the
quality assurance tests are kept together with the serial
number of each filter, its production and firing dates and the
precise filtration rates.
Project Information Officer, Ms. Tharanga
conducting CWF usage training for a group of
customers
Factory workers inspect the filter pots during
production
Photo by: Ms. Chritine Jayasinghe
Why is the CWF attractive to rural Sri Lankans?
The CWF’s advantages include its effectiveness, simplicity,
portability and affordability. It is economical and requires no
recurrent costs by the user. A CWF can filter from 1 – 3 litres
of water per hour, enough to meet the drinking water needs of
most families. Made mostly with indigenous materials by local
potteries the CWF is more environmentally friendly and
affordable than most other household safe water methods as
they are locally produced.
The CWF Project offers extensive consumer support. After the
distribution and hygiene promotion events, project staff visit
households twice. On the first visit, approximately one week
after distribution, staff observe and give advice on how the
CWFs have been assembled and located in the houses.
During the second visit, approximately four weeks later,
project staff carry out a presence/ absence test utilising a
UNICEF approved bottled hydrogen sulphide kit. The samples
of test water are kept for 24 hours. The presence of bacteria
will cause the sample water to turn black, while clean and
therefore safe water will remain colourless.
Convenient maintenance of the CWF includes monthly
scrubbing of the filter “pot” using a soft brush or cloth to clear
clogged pores and washing the plastic receptacle with soapy
water to prevent bacterial growth. While CWFs are lightweight
and portable, care must be taken during transport and
handling to avoid breakage. The CWFs have an average two-
year lifespan.
A Beneficiary from Galle studies the Hygiene Promotion
literature
Sri Lanka Red Cross Society
No 307 2/1, T.B Jayah Mawatha, Colombo 10, Sri Lanka
Tel: +94 11 535 700 /11 269 1095
IFRC/American Red Cross
No 62, Green Path, Colombo 3, Sri Lanka
Tel: -+94 11 237 5417
Cover Photograph by Mr. Tharanga Pradeep
Art work by M. Hewapathirana