Water safety plans : methodologies for risk assessment and risk management in drinking-water systems

摘要

Providing good and safe drinking-water is world-wide considered to be a fundamentalpolitical issue for public health protection, and must be the primary objective of water supplysystems. Drinking-water quality control has currently been based on detection of pathogens and toxic concentrations of chemicals by means of monitoring programs and compliance with national or international guidelines and standards, relying mainly on indicator bacteria and chemicals maximum concentration levels. However, this methodology is often slow, complexand costly. Even for sophisticated and well-operated systems these monitoring schemes have proved to be inefficient in preventing waterborne diseases like, for instance, Giardia or Cryptosporidium outbreaks. From this evidence we can conclude that end-product testing is a reactive rather than preventive way to demonstrate confidence in good and safe drinking-water.This justifies the need for the formulation of a new approach in drinking-water quality controlbased on understanding of system vulnerability for contamination and on preventive means and actions necessary to guarantee the safety of the water supplied to the consumer. Water safety plan is a concept for risk assessment and risk management throughout the water cycle from thecatchments to the point of consumption. This approach includes the identification of the hazards and introduction of control points that serve to minimize these potential hazards, providing for more effective control of drinking-water quality. This paper presents an overview of the first two years experience in developing and implementing a water safety plan in a Portuguese multimunicipalwater company. Since key personnel had contributed to the assessment of hazards andevaluation of corrective actions for control points, a greater understanding of water quality control and improvements on technical operation and performance have been registered, demonstrating good value for the methodology.