Water Treatment During Reconstruction
Practical Action
Water Treatment Classification
The World Health Organisation (WHO) ranks the treatment processes available according to their
technical complexity in Table 1, the higher ranking being more complex. It is usually the case
that the more complex the system, the higher the capital and operating costs.
Ranking
1
2
3
4
5
6
Examples of Treatment Processes
Simple Chlorination
Plain filtration (rapid sand, slow sand)
Pre-chlorination plus filtration
Aeration
Chemical coagulation
Process optimisation for control of DBPs
Granular activated carbon (GAC) treatment
Iron exchange
Ozonation
Advanced oxidation process
Membrane treatment
Table 1: Ranking of technical complexity and cost of water treatments
Source: WHO, 2008
In order to ensure water is free from both sediments and pathogens to an acceptable level, a
multi-stage treatment is most effective. The Practical Action technical brief Water Treatment
Systems describes methods to develop a multi-stage system.
Basic Water Treatment
In an emergency context, water is required immediately after a disaster for displaced populations
for both drinking and washing. The supply will most likely be provided by an external organisation
(Governmental or NGO-based relief agency) whose responsibility it is to ensure that the supply is
safe.
It is a general assumption in these scenarios that a sufficient quantity of safe water is more
desirable than a small quantity of high-quality water; the need to ensure all displaced people have
access to the supply is the primary objective. The SPHERE project is an initiative set-up by an
alliance of humanitarian agencies to ensure that principles and standards for humanitarian
responses are coordinated; the project has published a handbook detailing the minimum
standards for water quality in an emergency situation, which is available here.
Basic guidelines for treatment of a water source in an emergency scenario are as follows
(SPHERE, 2004):
Start with the best quality water available as treatment procedures are not perfect.
Filter source and encourage coagulation if possible.
Disinfect (although this may not be sufficient without further treatment).
Water quality should be tested for faecal contamination.
It should be assumed that with minimum standards of water supply met, there will be low
chemical contamination. All treatment in these circumstances should ensure that bacteriological
and physical contamination is minimised:
1) The removal of sediments and suspended solids through methods including aeration,
filtration, coagulation, storage, sedimentation and abstraction. The reduction in turbidity
of water supplies often leads to much more effective bacteria removal processes.
2) Disinfection to remove disease-causing bacteria (pathogens) through processes including
chlorination and solar treatment.
2