Exploring the effects of faults on the performance of a biological wastewater treatment process

Abstract

To prioritise which faults should be detected in a biological wastewater treatment process, and with what level of urgency, it is necessary to understand the effect that they have on the process. Using the Benchmark Simulation Model No. 1 and 2. (BSM1 and BSM2), several process and sensor faults were considered and their impacts on various cost, quality, and controller performance evaluation metrics analysed. Both the cost of treating the wastewater and the quality of the effluent were impacted in varying degrees of severity by the faults tested. The most influential faults in both models were decreases to autotrophic and heterotrophic growth rates, decreases to the heterotrophic death rate, and the inhabitation fault. It was shown that only larger fault sizes were significant, and the required speed of detection is dependent on the fault profile. Prioritising detection of the most influential faults was shown to have significant effects on monitoring requirements for fault detection and the subsequent complexity required of a fault detection system. A valuable takeaway was the similarity of results from BSM1 and BSM2; the consistency of the influential process faults suggests that systems that can be described by these models are likely affected by the same faults. HIGHLIGHTS Critical faults can be effectively highlighted through a simulation-based analysis of their effects.; Consistency of influential process faults across BSM1 and BSM2 provides transferrable knowledge.; Complexity of diagnostic algorithms can be reduced by knowing which faults should be prioritised.; Physical monitoring requirements and costs can be reduced if the monitoring focus is narrowed.;

Keywords

• activated sludge process
• biological wastewater treatment
• process faults
• process performance
• sensor faults