Use of fluorescence for real-time monitoring of contaminants of emerging concern in (waste)water: Perspectives for sensors implementation and process control

Abstract

The need to remove ubiquitously occurring contaminants of emerging concern (CEC) from water/wastewater represents a global challenge both in terms of developing efficient technologies and decreasing high energy demands of the water sector. In this context, online monitoring of the occurrence of CEC and their removal in (waste)water facilities play an important role in optimization of treatment processes. Fluorescence spectroscopy is a viable tool for ‘indirect’ CEC monitoring that is based on the correlations between CEC concentrations and those of dissolved organic matter (DOM). Among a wide range of fluorescence indexes have been proposed as surrogate parameters for water treatment applications, those measured at specific pairs of excitation/emission (ex/em) wavelengths can be implemented in commercially available or customized field-deployable fluorescence sensors thus enabling real-time and/or on-site CEC monitoring. This review examined results of the prior studies of ex/em pair options and selects those of them that are most useful for CEC monitoring in natural water environments, lab-/pilot-scale (waste)water treatment processes and ultimately in practical field applications. The approach of fluorescence-based monitoring is convenient for process control and optimization of CEC removal while concurrently saving energy and material demands of engineered (waste)water systems. This review also calls for further research of applications of fluorescence spectroscopy in (waste)water treatment and, more specifically, it provides a detailed workflow developed to select, test, and validate pairs of ex/em coordinates suitable for CEC monitoring in various types of (waste)water treatment processes.