Rapid detection of sewage spills from aging wastewater infrastructure and other sources is critical for minimizing the risk of introducing pathogens in urban waterways. Fluorescence spectroscopy has been successfully used to monitor anthropogenic, microbial sources of dissolved organic matter (DOM); however, little research has been conducted to assess the capabilities of portable, real-time fluorescence sensors to locate sewage inputs. DOM compounds, including aromatic amino acids (e.g. tryptophan) and chromophoric dissolved organic matter (CDOM), emit radiation in the ultraviolet spectrum when they are excited by wavelengths of about 280 nm and 120-325 nm, respectively. The fluorescence profiles of these compounds are well-documented, facilitating their identification. Previous storm water studies have demonstrated that sewage contains bacteria and other compounds that have tryptophan-like fluorescence, and that a strong correlation exists between tryptophan-like fluorescence intensity and the total aerobic bacteria counts and total coliforms during storm events. This study evaluates the capabilities of Cyclops-7F™ Submersible Sensors for tracking bacterial pollution in the San Diego River by comparing tryptophan and CDOM sensor readings in the field with samples collected at the same sites in Alvarado Creek and analyzed for bacteria and other chemical indicators of sewage contamination. This study is important for understanding the extent to which commercially available portable fluorometers can be used to pinpoint sewage leaks by tracking water quality in real time.
