Application of 2D fluorescence spectroscopy on faecal pigments in water : characterization of wastewater fluorescence and potential indication of faecal pollution

Sammanfattning: Drinking water pollution by faeces and associated enteric pathogens can cause serious health issues and outbreaks of diseases. A fast and reliable indication of faecal pollution is necessary to prevent the consumption of polluted water. This work aims at identifying faecal pigments in wastewater and discusses the possibility of using on-line fluorescence monitoring of faecal pigments in water as a tool for the detection of faecal pollution. Three faecal pigment standards, urobilinogen, urobilin, and stercobilin, as well as wastewater in- and outflows from five German wastewater treatment plants (WWTPs) were characterized by 2D fluorescence spectroscopy (using Excitation Emission Matrices), and by high performance liquid chromatography (HPLC) coupled with absorption (DAD) and fluorescence detection (FLD), as well as mass spectrometry (MS). Furthermore, tests on faecal pigment stability, reaction to zinc addition, kinetics, and pH influence on faecal pigment fluorescence were performed. With the obtained fluorescence data, a parallel factor analysis (PARAFAC) model for the detection and quantification of urobilin and stercobilin in real water samples was developed. An addition of zinc to the pigments in real water lead to a time-dependent fluorescence intensification of a factor >30 and red shift of the pigments’ fluorescence spectra, which can be used as a tool to detect low concentrations of faecal pigments in water. Urobilin and stercobilin were identified in all examined WWTP inflows. The results and literature study indicated that a degradation of faecal pigments during wastewater treatment may have taken place. In the wastewater of one treatment plant, fluorescein was detected. Fluorescence detection and quantification of faecal pigments in wastewater was possible with the help of zinc addition or prior enrichment, but more studies are needed to enhance the sensitivity of the method to be sensitive enough to detect faecal pollution in concentrations relevant for drinking or surface water monitoring. It was concluded that fluorescence detection of faecal pigments in water is promising as an early warning system, but in this study it did not prove sensitive enough to be used as a stand-alone method.