Household Water Treatment and Safe Storage Factsheet: Source ...

Household Water Treatment and Safe Storage
Fact Sheet: Straining
The Treatment Process
Potential Treatment Capacity
Very Effective For: Somewhat Effective For: Not Effective For:
Helminths
Protozoa
Turbidity
Bacteria
Taste, odour, colour
Viruses
Chemicals
What is Straining?
Straining water through a cloth has been
widely used for household water treatment
in many cultures for centuries. A common
sari cloth is usually used for this in South
Asia, for example.
How Does it Remove Contamination?
The pore size range in old (laundered) sari
cloth is 100–150 μm, but about 20 μm if the
cloth is folded four to eight times. The holes
allow water to pass but retain particles and
pathogens >20 μm.
Straining through sari cloth has been shown
to be effective in filtering out the plankton to
which cholera bacteria may attach
themselves, therefore reducing the risk of
cholera. This simple method can also filter
out many helminths and their eggs and
larvae.
Old sari cloth made of cotton was found to
be most effective in removing cholera based
on laboratory experiments (Colwell et al.,
2002). After several launderings, threads of
an old sari become soft and loose, reducing
the pore size, compared with new sari cloth.
Electron micrographs of a single layer of sari cloth
filters (Credit: Colwell et al., 2002)
Operation
Fold a large, clean piece of cloth seven to
eight times. Place the folded cloth over a
clean water container, and secure in place.
Pour water through the cloth into the
container. Wash the cloth in clean water
before using it again.
A woman uses a sari cloth to strain water