Detection of water quality failure events at treatment works using a hybrid two-stage method with CUSUM and random forest algorithms

Abstract

Near-real-time event detection is crucial for water utilities to be able to detect failure events in their water treatment works (WTW) quickly and efficiently. This paper presents a new method for an automated, near-real-time recognition of failure events at WTWs by the application of combined statistical process control and machine-learning techniques. The resulting novel hybrid CUSUM event recognition system (HC-ERS) uses two distinct detection methodologies: one for fault detection at the level of individual water quality signals and the second for the recognition of faulty processes at the WTW level. HC-ERS was tested and validated on historical failure events at a real-life UK WTW. The new methodology proved to be effective in the detection of failure events, achieving a high true-detection rate of 82% combined with a low false-alarm rate (average 0.3 false alarms per week), reaching a peak F1 score of 84% as a measure of accuracy. The new method also demonstrated higher accuracy compared with the CANARY detection methodology. When applied to real-world data, the HC-ERS method showed the capability to detect faulty processes at WTW automatically and reliably, and hence potential for practical application in the water industry. HIGHLIGHTS The novel HC-ERS combines the conventional SPC-type method with RF advanced machine-learning technique to ultimately detect WTW-level failure events.; When applied on unseen data HC-ERS proved to be capable of detecting failure events in WTW processes in near-real-time.; HC-ERS outperformed threshold-based and CANARY event detection methods.; HC-ERS showed potential for practical application in the water industry.;

Keywords

• cusum
• event recognition
• online monitoring
• random forest
• water treatment works