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The water supply system (WSS) is an anthropotechnical system whose reliability depends on proper human activity. Research indicates that 75% of WSS failures are due to human errors. The water treatment plant (WTP) is a key element of the WSS. The water treatment process requires human control as the operator. His task is to maintain an appropriate level of reliability and safety for the system by controlling the technological objects. The aim of the work was to assess the reliability of the WTP operator. The paper presents a Human Reliability Assessment (HRA) of the operator of the WTP using the Fuzzy-Bayes CREAM method. The values of the Human Error Probability (HEP) for operators were determined, which are key to carrying out further analyses of the human impact on the reliability and operational safety of anthropotechnical critical infrastructure systems. The HEP value of the water treatment plant operator varies in the range of 0.0005–0.0746 (depending on the technological process). Identification of new threats related to the impact of the human factor on the WSS's functioning and taking them into account in reliability calculations will allow for a better representation of actual operating conditions. [ABSTRACT FROM AUTHOR]

The main goal of this work is to show the new approach to determining safety technological levels (SLs) in terms of water quality and its chemical stability, as well as issues of water corrosion properties in water distribution systems (WDSs), due to the fact that water supply pipes are prone to corrosion. In the paper the methodology of determining the risk associated with threat to technical infrastructure was considered. The concept was studied on the basis of real operational data from the water treatment plant. The probability of exceeding the individual parameters for WTPI is slightly larger than for WTPII, which means that this water treatment process may cause lack of chemical stability in the water supply network. Operators should anticipate in the process of designing water distribution system, using proper materials, as to ensure an adequate level of safety from the water source to the water recipient. It should be noted that it is necessary to adjust the material of internal installation of water supply networks to the parameters of the water. At present, there are no correlations between the designing step and water parameters. It was concluded that to protect the water supply infrastructure, which belongs to critical infrastructure, water company should put more emphasis on distribution of stable water that has not potentially corrosion properties. Some suggestions were made for the protection of WDS and to ensure safety of system functioning and long-term usability of water pipes.

The article presents research results of the introduction of powdery activated carbon to the existing technological system of the groundwater treatment stations in a laboratory, pilot plant and technical scale. The aim of the research was to reduce the content of organic compounds found in the treated water, which create toxic organic chlorine compounds (THM) after disinfection with chlorine. Nine types of powdery active carbons were tested in laboratory scale. The top two were selected for further study. Pilot plant scale research was carried out for the filter model using CWZ-30 and Norit Sa Super carbon. Reduction of the organic matter in relation to the existing content in the treated water reached about 30%. Research in technical scale using CWZ-30 carbon showed a lesser efficiency with respect to laboratory and pilot-plant scale studies. The organic matter decreased by 15%. Since filtration is the last process before the individual disinfection, an alternative solution is proposed, i.e. the second stage of filtration with a granular activated carbon bed, operating in combined sorption and biodegradation processes. The results of tests carried out in pilot scale were fully satisfactory with the effectiveness of 70–100%.

The functional safety of the water supply system should be implemented by using risk standards, available reliability methods or with the use of Water Safety Plans, which are dedicated to all water supply companies. The constantly updated knowledge and the ability to carry out risk analysis and assessment based on the available tools, allows for effective decision-making process in order to minimize the health risk and the negative effects posed by the risk of secondary water pollution in the water supply network. The main aim of the article was to propose an original model for estimating the risk of secondary water pollution in the water supply system. The proposed model is based on a four-parameter risk matrix. The presented methodology containing a matrix proposal and criteria on a descriptive-point scale can be used in risk analysis and assessment both in qualitative and quantitative terms. Additionally, it will have a positive impact on the effectiveness of the water supply security management process in water supply companies. For the proposed model, a calculation example for a water supply network operated in south--eastern Poland has been presented. [ABSTRACT FROM AUTHOR]

The aim of the study is to analyse the seasonality of water losses from a collective water-supply system (CWSS) on the example of a provincial city located in south eastern Poland. The analysis was based on exploitation data obtained from the water-supply company for the period 2012–2016. For the analysis of seasonality a method based on average homogeneous sub-periods was used, with a relative seasonality index and the absolute levels of seasonal fluctuations being determined. Water losses from the analysed CWSS are also characterised using unit water-volume indicators within the water supply network. Over the research period, the volume of water produced and sold was found to decline, even as the number of inhabitants using the network increased. On the other hand, there is a growing demand for water used for own purposes by company, as related directly to their development. Water losses and values determined for the water-loss volume indicator both show a downward trend for the analysed CWSS. It is further observed that, in January, March and May, the loss of water is above average, while the volume of water lost in the other months is below average.

The subject of the publication is the analysis and assessment of failure rate of the water supply network in a district city located in south-eastern Poland. The analysis was based on the failure rate index. In addition, the paper uses the Bayes theorem to determine the probability of failure of water supply network. The exploitation data obtained from the water supply company were used in the work. It was found that the water supply network of the analysed city is characterized by good technical condition.

Many phenomena are characterized by unevenness and variability in time, so-called periodic fluctuations, of which seasonal variations are a special case. In water supply systems, the failures of water pipes are also characterized by unevenness during the year. Seasonality is especially evident when the failures are analysed at particular times of the year. The main purpose of this paper is to present the problems of failures in water supply network caused by seasonal changes, to determine seasonal indicators and to give an example of the system failure analysis for the selected city of south-eastern Poland. The analysis was based on actual operational data obtained from water supply company.

The subject of the work is the analysis and assessment of the risk of biological instability of water. The lack of water stability causes the increased susceptibility of the distribution system to secondary microbial contamination of water and constitutes a hazard for consumers’ health. The risk is expressed as the loss of water supply safety and distinguishes a failure of not meeting certain water quality parameters that can influence physico-chemical parameters and the bacteriological quality of the water supplied to the consumers. In the paper the method of analysing and evaluating the risk of loss of biostability of tap water is presented. The presented analysis was performed on the basis of the operating data from the water treatment plant.

The aim of the study was to determine the probability of exceeding the normative values of microbiological parameters in tap water intended for human consumption depending on the operating time of the installation. Based on the results of microbiological testing of water, models of microorganism growth were developed and the times of the installation operating until exceeding the normative values for selected parameters were determined. The installation operating times were used in life data analysis, which made it possible to examine the probability of water supply with appropriate microbiological parameters. For individual measurement cycles, the time of exceeding the normative parametric value of the total number of microorganisms value at a temperature of 22°C parameters was obtained in the range of 9.38–34.85 h, while for exceeding the normative parametric value of the total number of microorganisms value at a temperature 37°C parameter was obtained in the range of 29.69–48.00 h. The probability of human consumption of water that does not meet microbiological criteria increases with the duration of its stay in the domestic distribution system. Exceeding the normative parametric value of the total number of microorganisms at 22°C may occur after 11.73–41.90 h of installation operation depending on the adopted probability level (10%–99%), while exceeding the normative parametric value for the total number of microorganisms at 37°C may occur after 29.63–81.24 h. Test results can be used for identifying hazards as part of the analysis and risk assessment of domestic distribution systems. [ABSTRACT FROM AUTHOR]