Design of an IoT-Integrated Lab-Scale Sequencing Batch Reactor with Real-Time Water Quality Monitoring

Abstract - Decentralized wastewater treatment is increasingly important for urban sustainability, and the Sequencing Batch Reactor (SBR) is a compact and flexible option. However, SBRs are usually operated on fixed timers and checked by manual sampling, which leaves operators blind to rapid changes inside the tank. This paper presents the design, fabrication and monitoring system of a 25 liter lab-scale SBR for domestic wastewater, built with low-cost Internet of Things (IoT) hardware. The reactor is sized from laboratory characterization of raw sewage collected from a campus sewage treatment plant (BOD 125 mg/L, TSS 136 mg/L, pH 7.59). It runs a five-phase cycle of fill, react, settle, decant and idle. Sensors for pH, total dissolved solids, turbidity, temperature and water level are connected to an Arduino Uno, which passes the data to an ESP32 microcontroller for transfer to a web dashboard. The sensors were calibrated against laboratory instruments and agreed with the manual readings to about 98 percent for pH and total dissolved solids. The dashboard provides live values, trend graphs, batch phase display, alarms, maintenance records and report export. The work shows a cost-effective path to adding digital oversight to decentralized biological treatment.