Optimization of the Operation of Wastewater Treatment Plants through the Integration of Industrial Automation Architectures: Case Study in the Conventional Activated Sludge Process under NOM-001-SEMARNAT-2021

Abstract

Conventional activated sludge wastewater treatment plants often rely on manual control, limited online instrumentation, and delayed laboratory analyses, which can restrict their response to hydraulic and organic-load fluctuations. This study developed an integrated industrial-automation proposal for the wastewater treatment plant examined under the requirements of NOM-001-SEMARNAT-2021. The proposed architecture combines a Siemens SIMATIC S7-1200 programmable logic controller, HMI/SCADA supervision, variable-frequency drives, spectrophotometric analytical sensors, electromagnetic flowmeters, radar level sensors, and process interlocks. A quantitative, non-experimental, cross-sectional, and prescriptive approach was organised into four phases: technical diagnosis, assessment of operational vulnerabilities, automation engineering design, and economic feasibility analysis. The diagnosis identified mechanical risks associated with pump dry running, environmental risks related to overflow and disinfectant-dosing variability, and biological risks linked to unstable dissolved-oxygen conditions. The proposed control strategy uses continuous measurements and automated feedback to support dissolved-oxygen regulation, equipment protection, sludge-management decisions, effluent-quality monitoring, and historical data traceability. The design also establishes a technical basis for monitoring operational variables relevant to regulatory compliance. As the proposal was not implemented experimentally, its expected operational and economic benefits remain subject to field validation. Nevertheless, the study provides a structured, practical, and replicable engineering framework for modernising conventional activated sludge facilities through integrated automation.