PLC–SCADA–Integrated Electrical Automation Frameworks for Process Optimization in Water and Wastewater Treatment Facilities

Abstract

This quantitative study examined the operational impact of PLC–SCADA–integrated electrical automation frameworks on process optimization in water and wastewater treatment facilities using high-frequency operational data and quasi-experimental evaluation methods. A longitudinal interrupted time series design was applied to 720 daily observations, equally divided between pre-integration and post-integration periods, with statistical adjustment for influent flow, temperature, operating regime, and major equipment availability. The findings showed consistent and statistically significant improvements across efficiency, stability, workload, and event-based performance indicators. Energy intensity exhibited an immediate post-integration level reduction of 0.041 kWh/m³ (95% CI −0.056 to −0.026, p < .001) and an additional post-integration trend improvement of 0.00018 kWh/m³ per day (p = .002), indicating both immediate and sustained efficiency gains. Process stability improved through a reduction in composite stability deviation of 0.043 units (p < .001) and a 22% decrease in excursion event rates (IRR = 0.78, 95% CI 0.70–0.87). Supervisory workload outcomes improved markedly, with alarm rates declining by 28.4 alarms per day (p < .001), alarm flood events reduced to 73% of baseline frequency (IRR = 0.73, p < .001), and manual override time reduced by 1.6 percentage points (p < .001). Chemical intensity showed a statistically significant immediate reduction of 2.6 mg/L (p = .001) but no significant post-integration trend change. Mechanism-oriented analyses indicated a 9.2% reduction in VFD speed variability and a 0.36-unit reduction in loop oscillation proxy scores (p < .001), supporting a control-stability pathway for observed outcomes. Sensitivity analyses using storm-only periods, influent-matched windows, and outage-excluded datasets produced consistent effect directions and comparable magnitudes. Overall, the results demonstrated that PLC–SCADA–electrical integration was associated with measurable and robust improvements in energy efficiency, process stability, abnormal-event frequency, and operator workload under real treatment-plant operating variability.