PLC-Based Water Quality Monitoring and Separation System

Water quality monitoring is an essential fundamental for industrial process, human health and environmental sustainability. This thesis presents the development of an automated water quality monitoring and separation system which is PLC controlled and utilizes Potential of Hydrogen (pH), and Total Dissolved Solvents (TDS) sensors to assess water quality and display real time values on a Human-Machine Interface (HMI). Based on the measured parameters (pH and TDS), the system provides indications on the HMI, guiding the user to manually select the appropriate drainage compartment. There is often a noticeable gap between the way industrial automation is taught in classrooms and the practical skills that engineers need in real-world applications. This thesis presents the development of a comprehensive PLC-based control system designed to emulate a scalable industrial process within a laboratory environment. The system uses a Siemens PLC S7-1200 1215C AC/DC/RLY for control, with an HMI (KTP700 Basic PN) for user interaction. The system performs the following functions: • Initiates water pumping into the storage tank upon operator command. • Measures water quality parameters (pH and TDS) in real time using integrated sensors. • Displays live feedback of measured values and status messages on the HMI. • Generates event-based text indications with variable visibility to classify water quality. • Enables manual selection of drainage, directing water either to Compartment A (clean water) or Compartment B (contaminated water). Before moving to the real hardware, the system was first tested in a virtual setup with Siemens PLCSIM, which helped check the control logic and spot any design problems early on. Following successful simulation, the project progressed through the full development cycle: the mechanical concept of the tank and supporting structure was created in SolidWorks, and 3D printed by using Cura Software compatible with AnyCube Printer. The complete assembly was integrated with the electrical and control hardware. Control logic was implemented and optimized in Totally Integrated Automation (TIA) Portal. Calibration and uncertainty analysis formed an important part of this work. The pH sensor was calibrated using two standard buffer solutions (pH 4.00 and pH 10.00) through a two-point linear calibration (gain and offset adjustment), bringing sensor values in approximation with the buffer values. The TDS sensor exhibited a baseline offset of +5.35 ppm in the absence of dissolved solids, which was corrected by subtracting this baseline error from all readings. The repeatability of the two sensors was also evaluated by means of the experimental standard deviation of ten repeated readings in different solutions (pH 4, pH 10, tap water, salt water, and lemon water). Analysis showed that the uncertainty from the experimental measurements was minimal relative to the other contributing factors. Further Improvements could integrate Supervisory Control and Data Acquisition (SCADA) system, which will allow remote monitoring, auto drainage system instead of human interference for real-time water quality analysis.