Assessing validation and reliability of water and wastewater treatment processes using Bayesian techniques

Abstract

Water and wastewater treatment systems have key roles in protecting public health. To maintain public confidence, techniques are required to quantitatively validate their performance for achieving satisfactory water quality and to characterise system reliability. Water quality management, especially potable water reuse, is transitioning to a point where validation and reliability assessment will be essential. Quantitative validation and reliability analyses can assist in determining factors affecting performance, calculating system failure probabilities and supporting decision-making. However, current water quality management guidelines and practices do not promote validation and reliability assessment tools or methods. Research presented in this thesis identifies validation and reliability analysis tools and demonstrates their applicability for water and wastewater treatment. Following a review of commonly used candidate analysis tools, Bayesian Networks (BNs) and methods were identified as very promising for validation and reliability assessment. Applications of BNs and Bayesian methods were investigated in six diverse water and wastewater treatment settings (i.e. activated sludge, ultrafiltration, ozonation, chlorination, UV disinfection and a multiple barrier system). These cases considered a range of issues including evaluation of monitoring parameters for log reduction values (LRVs), optimising LRV calculations, system reliability assessment, and multi-barrier evaluation. These were selected to represent problems and limitations encountered with water reuse. BNs and Bayesian methods were found to be flexible and applicable to a wide range of cases and problems. The tools were shown to be applicable to systems where high levels of assessment and understanding of water quality are essential. The findings should now serve as templates to facilitate validation and reliability assessment of full scale water reuse applications. In conclusion, it is proposed that my findings will be of significant value to the water industry and should aid in the further development of potable water reuse, while providing enhanced protection of public health to water supply customers.