8.2.3  Identify the hazards and hazardous events

It is important to identify the potential hazards at each stage of the water supply process (see Box 8.1). Hazardous events in this context are defined as events that can introduce hazards into the water supply. A hazardous event can also be considered a source of a hazard. Table 8.1 gives examples of hazardous events and hazards that can affect different parts of a water supply system.

Table 8.1  Possible hazards in a water supply system. (Adapted from Bartram et al., 2009)

Hazardous event (source of hazard)Associated hazardComponent of water supply system affected
AgricultureMicrobial contamination from animal excreta, pesticides, nitrates from fertiliser useCatchment
MiningChemical contaminationCatchment
Interruption of power supplyInterruption of treatmentTreatment
Disruption of disinfection due to lack of disinfectant supplyUnsafe water goes to consumersTreatment
Mains burstContaminants getting into pipelineDistribution network
Illegal connectionsContamination of water supply by back-siphonageDistribution network

Site visits are an effective way of ensuring all possibilities are covered (Figure 8.4). It is important to speak to the people who work at the locations concerned as they will have local knowledge that may not necessarily be in the paperwork related to the facility.

Figure 8.4  Testing water quality is an important part of hazard assessment.

8.2.2  Describe the water supply system

8.2.4  Carry out a risk assessment and prioritise the risks