Design of control systems for a waste-water treatment plant and safety improvement through risk assessments and effective alarm management

The thesis explores the design and implementation of control systems for wastewater treatment plants, focusing on the Suanfarma facility in Rovereto. The main objective was to automate wastewater treatment lines, conduct a risk analysis based on PFMEA, and improve efficiency, safety, and compliance with emission limits. To identify the critical elements, the plant was divided into three main sections, spent mycelium line, high COD line and low COD line, which were further subdivided into blocks, i.e. according to different plant equipment each with its own characteristics and criticalities. Flow diagrams (BFDs) were used to analyse material flows, identify bottlenecks, and optimize processes. Key controlled variables (CVs) and manipulated variables (MVs) were identified, and graphical analysis demonstrated how adjusting MVs could keep CVs within target ranges. Data from the plant were collected using PI Datalink system, organized into detailed flowsheets, and used to develop control strategies. All information was documented in the User Requirements Specification (URS) to guide automation specialists. Risk analysis identified potential hazards, assessed their impact, and recommended solutions, including safety protections and alarm systems for emergencies. The new control logics were implemented and tested, enabling secondary loops or alarms to activate during failures and prompt operator intervention. The alarm system was updated to reduce redundancy, improve clarity, and prioritize critical alerts, ensuring faster responses to emergencies. Optimization of the plant processes resulted in improved efficiency and safety, with the control strategies adapting well to changing loads despite some minor precision issues. Updated manuals and a new flowsheet of the WWT plant were created to reflect the changes. The automation project effectively minimized manual tasks while enhancing the efficiency of equipment and wastewater treatment processes. Alarm management systems became clearer and more effective, ensuring safer operations. Overall, the project demonstrated substantial improvements in the plant’s performance, achieving stable operations, regulatory compliance, and enhanced safety.