Summary

In this Study Session, you have learned that:

• Water supplies may be cut off in emergencies caused by natural events or human actions. Natural factors could be droughts, floods or earthquakes, while human-related emergencies can arise from accidents caused by human error, deliberate poisoning of the water supply or neglect (as exemplified by Case Study 14.1).
• During emergencies water may be supplied via delivery by tankers, use of plastic bottles or treatment of available poor-quality water in the home using filtration and disinfection.
• Filtration at household level can be achieved by using cloth, sand or a ceramic pot. Disinfection can be undertaken by boiling or solar methods, or by using chlorine or commercial water treatment products.
• Emergency water treatment is needed when an internally displaced population or refugees have to be provided with water urgently. It is preferable to use groundwater as it is likely to be less polluted than surface water.
• Simple and complex systems for emergency water treatment are available. For sustainability simple systems are preferable.
• The coagulant most commonly used in emergency water treatment is aluminium sulphate, as it is widely available. A simple emergency water treatment system comprises coagulation and flocculation, sedimentation, and chlorination, while a complex unit might incorporate coagulation and flocculation, sand filtration, microfiltration, and chlorination.