Functional Safety Concept to Support Hazard Assessment and Risk Management in Water-Supply Systems

Within the frame of upgrading and modernisation of the Water Supply System (WSS), our work is focussing on the safety systems/devices implemented or that should be implemented in the WSS. The implementation of safety systems is supposed to reduce hazard occurrence and hazardous consequences in case of a WSS unsafe disruption. To assess this reduction, we preconise the use of the safety integrity levels standards. The implementation of the safety systems/devices is undertaken on the ground of the multi-barriers safeguard approach. The “Water Contamination Hazard” is considered in the paper. A case study is presented, assessed and conclusions are drawn. The methodology presented in the paper and the results of the case study assessment will contribute to the decision-making regarding the upgrading of the safety and the performance of the WSS.

Consumers’ Perceptions of the Supply of Tap Water in Crisis Situations

This paper first presents the results of polling on the subject of potable water in crisis situations, with respondents from south-eastern Poland’s Subcarpathian region asked for their opinions on the level of nuisance associated with water supply interruptions and water quality, levels of consumption and water companies’ quality of service. Among the respondents 53% regard the quality of the water they receive as satisfactory, while a quarter see it as only average. However, respondents are relatively satisfied with the corporate response when supplies are interrupted, as methods and means of notification are judged effective by 60%. Continuing with work to assess possibilities for water companies to improve their performance in crisis situations, the present study generates an Analytical Hierarchy Process allowing recipients to determine importance criteria where quality of service is concerned. This could facilitate management by water companies, providing for centralised control and comparison that help secure services of appropriate quality. The process can also help protect different groups of recipients, as safety is evaluated through analysis of functioning, and of failures and losses.

Water Network-Failure Data Assessment

The water-supply system is one of the basic and most important critical infrastructures. Water supply service disruption (water quality or quantity) may have serious consequences in modern societies. Water supply service is subject to various failure modes. Failure modes are specified by their degradation mechanisms, criticality, occurrence frequency and intensity. These failure modes have a random nature that impacts on the network disruption indicators, such as disruption frequency, network downtime, network repair time and network back-to-service time, i.e., the network resilience. This paper focuses on the water leakage failure mode. The water leakage failure mode assessment considers the unavoidable annual real water losses and the infrastructure leakage index recommended by the International Water Association’s Water Loss Task Force specialist group. Probabilistic statistical modelling was implemented to assess the seasonal index, the failure rates and the expectation value of the “mean time between failures.” The assessment is based on real operational data of the network. Specific attention is paid to the sensitivity of failures to seasonal variations. The presented methodology of the analysis of the water leakage failure mode is extendable to other failure modes and can help in developing new strategies in the management of the water-supply system in normal operation and crisis situations.