Water Treatment During Reconstruction
Practical Action
Advanced/Permanent Water Treatment
In more advanced reconstruction contexts, where populations have moved from emergency
shelters into more permanent stages of housing, there is more scope to employ advanced methods
of water treatment. It is likely that water sources will no longer be distributed and treated by relief
agencies, and it may be that higher levels of contamination exist. In these cases, there will be a
greater requirement of the community/individual to filter and disinfect the water thoroughly with
more advanced techniques.
There are a variety of technologies available to apply more advanced water treatment processes.
The feasibility of their installation can depend on numerous factors, including cost, labour
requirements and available materials. In general, these options tend to be large-scale and/or more
expensive, where the high initial investment and complexity can lead to a secure water source
over an extended period. Many of these technologies require external support, with an aim to
ensuring the community/user can independently operate and maintain after installation.
Bio-Sand Water Filters
Bio-Sand Filters are a recent, innovative approach to household water treatment, whereby a
containing body is filled with gravel and sand layers which allow water to diffuse through them.
The water drain is then pumped back up above the sand layer, creating an active bio-film on the
surface of the sand, which enables efficient purification of water that passes through.
The filter can produce up to 60 litres of safe water per hour, removing more than 90% of faecal
coliform, 100% of protozoa and helminthes, 95 to 99% of zinc, copper, cadmium, and lead, and
all suspended sediments. However, further treatment of the water is probably required to remove
dissolved compounds such as salt and fluoride or organic chemicals such as pesticides and
fertilizers, which pass through the filter.
The technology has several advantages when considering aspects of PCR, including the fact that
it utilises many materials that are available locally in poor areas. The filter can produce a high
flow rate and is an effective and durable method.
Contaminated
water in
Biologically active
bio-film develops
on the surface of
the sand
Sand
Gravel
Concrete body
cast on site in
shuttering
mould
6
Wooden
cover
Diffusion
plate
Outlet pipe
and tap for
clean water
Coarse
sand layer
Figure 3: A typical bio-sand filter cross section
Illustration: Practical Action