Davey, K.Abdul Halim, N.Lewis, D.2013-04-042013-04-042012Proceedings of CHEMECA 2012: quality of life through chemical engineering, held in Wellington, New Zealand, 23-26 September, 2012: pp.1589-15969781922107596http://hdl.handle.net/2440/76450UV irradiation is an alternative to widely used chemical disinfection to produce potable water. Failure of a well-run, well-maintained UV plant can lead to catastrophic and enduring public health effects, with or without fatalities. Failure is defined as the unexpected survival of levels of pathogenic Escherichia coli. Friday 13th failure modelling (Fr 13) is an emerging method for new quantitative risk assessments of unexpected failure in process plant due to "within system" chance (stochastic) changes. In this original research a new Fr 13 risk assessment of a simplified unit-operations model for UV irradiation for potable water is presented for the first time. A comparison is made between the predictions from a traditional, single point assessment and Fr 13 model using established UV inactivation kinetics for E. coli. A process risk factor (p) is synthesised in the Fr 13 model and is solved using a refined Monte Carlo simulation with Latin Hypercube sampling. Results reveal that 47 in every 10,000 continuous UV operations can fail unexpectedly with a tolerance of 10% on the design level of reduction in E. coli. This translates, on average, to an unexpected survival of E. coli each 0.58 years of continuous operation. This new insight is not available from traditional assessments, with or without sensitivity analyses. Practical methods of reducing unexpected failure and improving process technology in UV plant for potable water are briefly discussed.en© 2012 Engineers AustraliaRisk assessmentdrinking waterultraviolet radiationConference paper002012503021453Davey, K. [0000-0002-7623-9320]