Calibration of UV/Vis spectrophotometers: A review and comparison of different methods to estimate TSS and total and dissolved COD concentrations in sewers, WWTPs and rivers

Abstract : UV/Vis spectrophotometers have been used for one decade to monitor water quality in various locations:sewers, rivers, wastewater treatment plants (WWTPs), tap water networks, etc. Resulting equivalentconcentrations of interest can be estimated by three ways: i) by manufacturer global calibration; ii) bylocal calibration based on the provided global calibration and grab sampling; iii) by advanced calibrationlooking for relations between UV/Vis spectra and corresponding concentrations from grab sampling.However, no study has compared the applied methods so far. This collaborative work presents a comparisonbetween five different methods. A Linear Regression (LR), Support Vector Machine (SVM),EVOlutionary algorithm method (EVO) and Partial Least Squares (PLS) have been applied on various datasets (sewers, rivers, WWTPs under dry, wet and all weather conditions) and for three water qualityparameters: TSS, COD total and dissolved. Two criteria (r2 and Root Mean Square Error RMSE) have beencalculated - on calibration and verification data subsets - to evaluate accuracy and robustness of theapplied methods. Values of criteria have then been statistically analysed for all and separated data sets.Non-consistent outcomes come through this study. According to the Kruskal-Wallis test and RMSEs, PLSand SVM seem to be the best methods. According to uncertainties in laboratory analysis and ranking ofmethods, LR and EVO appear more robust and sustainable for concentration estimations. Conclusions aremostly independent of water matrices, weather conditions or concentrations investigated.
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Submitted on : Thursday, April 5, 2018 - 8:20:36 AM
Last modification on : Monday, May 13, 2019 - 11:19:30 AM

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Mathieu Lepot, Andres Torres, Thomas Hofer, Nicolas Caradot, Günter Gruber, et al.. Calibration of UV/Vis spectrophotometers: A review and comparison of different methods to estimate TSS and total and dissolved COD concentrations in sewers, WWTPs and rivers. Water Research, IWA Publishing, 2016, 101, pp.519 - 534. ⟨10.1016/j.watres.2016.05.070⟩. ⟨hal-01758993⟩

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