Household water treatment systems
Practical Action
The following processes for treating water will be described, with directions to links for further
reading:
Aeration
Sedimentation
Coagulation
Roughing filters
Rapid sand filters
Slow sand filter
Chlorination
UV Treatment
Distillation
Reverse Osmosis
Activated carbon
Multi-Stage Filtration
Water is
sprayed over
stones
25mm stone
150mm deep
Aeration
Aeration is used in order to remove
dissolved iron and manganese – these
can give water an unpleasant taste and
stain food and food and clothes with a
brownish colour. The iron and
manganese can be turned into sediment
using this process which is easier to
remove.
A simple aeration system can be set up
on a rural basis using a system
comprising of four cylinders. The top
three cylinders have a mesh or sieve at
the bottom that holds small stones or
sand, and have ventilations slots in the
side walls. The two cylinders at the top
contain stones of about 25mm in
diameter to a depth of 150mm and the
third cylinder contains coarse sand to a
depth of 300mm. Water is piped to the
top of the system where it is sprayed
onto the layer of stones. The water drips
down though the layers of stones
becoming more aerated and the sand
layer removes the sediment. Water is
collected in the forth cylinder at the
bottom of the column where it can then
be collected. The sand needs to be
replaced once a month.
25mm stone
150mm deep
Coarse sand
300mm deep
Water is
collected in
cylinder and
withdrawn
through tap
Figure 2: A cylinder aeration
system. (Illustration by A. Elias
based on Pickford (1977))
Other configurations of aeration tanks are described in the Slow Sand Filtration Manual.
Sedimentation
Sedimentation is often required due to the large silt content found in water extracted from rivers.
Water is passed through a large tank slow enough for solid particles to settle. It is easier to pass
water through a filter once the larger solids have been removed, and this is usually done through
a sedimentation process. Coagulation chemicals may be used to speed up the process but it is
often the case that these are not available to rural communities.
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