Rapid Identification of Industrial Wastewater Discharges in Municipal Sewer Networks Based on Three-Dimensional Fluorescence Spectroscopy and Spectral Angle Mapping
The increasing complexity of pollutant sources in municipal wastewater networks, driven by unauthorized industrial discharges, poses significant risks to the stable operation of wastewater treatment plants. This study, conducted in an industrial park in Ningbo, Zhejiang Province, developed a source apportionment method using excitation-emission matrix (EEM) fluorescence spectroscopy combined with spectral angle mapping (SAM). A pollution fingerprint database was constructed from wastewater samples of six representative enterprises (A–F) and municipal sewer samples. The SAM algorithm demonstrated high sensitivity and stability in detecting changes in water composition, with spectral angle values showing a strong linear correlation (R² > 0.88) with the volume ratio of enterprise wastewater in mixed samples. This enabled both qualitative identification and quantitative estimation of pollution sources. Field application over a 12-hour monitoring period identified two enterprises as major contributors to organic matter and nitrogen during critical pollution episodes, consistent with trends in DOC, TN, and UV254. The proposed EEM+SAM approach offers a non-invasive, high-throughput method for real-time monitoring and source tracing of multi-source pollution in complex sewer systems, providing a scientific basis for pollution accountability and precise enforcement.