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In situ UV-Vis spectroscopy to estimate COD and TSS in wastewater drainage systems

Ultraviolet-visible (UV-Vis) spectroscopy is a promising tool for fast and simple evaluation of wastewater quality, as it delivers spectra that may be correlated to various aggregate wastewater quality parameters, such as Total Suspended Solids (TSS) and Chemical Oxygen Demand (COD). Its application in drainage systems has scarcely been reported and is a step forward in water quality monitoring. Partial Least Squares (PLS) calibration models were developed for TSS and COD prediction, based on UV-Vis spectra. Spectra were acquired in two sites, in-line and off-line. Three approaches for model development were studied. Model evaluation statistics and guidelines were assessed, which allowed grading of the models from unsatisfactory to very good. Most of the developed models were rated very good according to those guidelines. The overall results strongly indicate UV-Vis spectra to be reliable for TSS and COD estimation in sewer systems, despite the rapid variations in hydraulic conditions and water quality.