Rehabilitating water treatment works after an emergency
Technical note 6 on drinking-water, sanitation and hygiene in emergencies
Step 2: What to do first
The first requirement is to get water into the distribution system quickly. Water quantity (rather than quality) provides the main health and social benefits during an emergency. Treatment, therefore, can be limited in the first instance, but ensure that the water is free of gross contaminants that may block or damage pipes and pumps.
The first step in improving water quality is to reduce the need for treatment by minimizing the level of pollution at source. Providing environmental sanitation services (such as the management and disposal of excreta, solid waste and rainwater), controlling erosion, reducing agricultural pollution and restricting direct public access to the water source can reduce the amount of contaminants that have to be removed from the water (Figure 6.2). In many cases, restoring a sewage collection and treatment system may be a greater priority than completely rehabilitating the water treatment works.
The priority for treatment works rehabilitation is shown in Figure 6.4. If, however, the water is relatively clear, chlorination can be introduced at an earlier stage. This may involve the installation of temporary pipelines to by- pass damaged sections of the plant. If major components of the works such as storage reservoirs and sedimentation tanks are badly damaged, their repair or replacement will be expensive and take a long time. During the emergency phase they should be replaced with temporary equipment such as portable storage tanks.