Comparison of Monitoring Methods for Total Organic Carbon using Optical Sensors in a Wastewater Treatment Plant

This study aimed to determine the optimal installation method for total organic carbon (TOC) online monitoring that facilitates easy maintenance and ensures stable water quality data collection, thereby enhancing the operational efficiency of bioreactors in wastewater treatment plants. Two monitoring configurations were tested at the bioreactor inlet: (1) a submerged type, with a sensor placed directly in the treatment process flow, and (2) a side-stream circulation type, with a sensor placed in a tank receiving influent via an underwater pump. Sensors continuously collected data at second-level intervals, which were processed into 5-minute averages for analysis. Both configurations achieved a utilization rate exceeding 99%, and the average TOC concentrations were 34.34 mg/L for the circulation type and 33.77mg/L for the submerged type, showing similar fluctuation trends. However, the submerged type exhibited relatively greater variance in measurements. Optimal cleaning cycles were estimated at five weeks for the side-stream type and one to two weeks for the submerged type. These findings suggest that the side-stream circulation configuration offers better maintenance efficiency and reliable data acquisition, making it a recommended option for stable TOC monitoring in sewage treatment processes.