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.
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 equivalent concentrations of interest can be estimated by three ways: i) by manufacturer global calibration; ii) by local calibration based on the provided global calibration and grab sampling; iii) by advanced calibration looking 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 comparison between 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 data sets (sewers, rivers, WWTPs under dry, wet and all weather conditions) and for three water quality parameters: TSS, COD total and dissolved. Two criteria (r(2) and Root Mean Square Error RMSE) have been calculated - on calibration and verification data subsets - to evaluate accuracy and robustness of the applied 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, PLS and SVM seem to be the best methods. According to uncertainties in laboratory analysis and ranking of methods, LR and EVO appear more robust and sustainable for concentration estimations. Conclusions are mostly independent of water matrices, weather conditions or concentrations investigated.
University of Lyon, INSA Lyon, DEEP Laboratory (Déchets Eaux Environnement Pollutions), EA 7429, F-69621 Villeurbanne Cedex, France. Electronic address: m.j.lepot@tudelft.nl.
Mathieu
M
Lepot
Research Group Cienca e Ingenieria del Agua y el Ambiente, Faculty of Engineering, Pontificia Universidad Javeriana, Carrera 7 No. 40-62, Bogota, Colombia.
Andres
A
Torres
Graz University of Technology, Institute of Urban Water Management and Landscape Water Engineering, Stremayrgasse 10/I, A-8010 Graz, Austria.
Thomas
T
Hofer
Kompetenzzentrum Wasser Berlin gGmbH, Cicerostrasse 24, D-10709 Berlin, Germany.
Nicolas
N
Caradot
Graz University of Technology, Institute of Urban Water Management and Landscape Water Engineering, Stremayrgasse 10/I, A-8010 Graz, Austria.
Günter
G
Gruber
University of Lyon, INSA Lyon, DEEP Laboratory (Déchets Eaux Environnement Pollutions), EA 7429, F-69621 Villeurbanne Cedex, France.
Jean-Baptiste
JB
Aubin
University of Lyon, INSA Lyon, DEEP Laboratory (Déchets Eaux Environnement Pollutions), EA 7429, F-69621 Villeurbanne Cedex, France.
Jean-Luc
JL
Bertrand-Krajewski
D002138:Calibration; D016018:Least-Squares Analysis; D045483:Rivers; D060388:Support Vector Machine; D062065:Wastewater
D062065:Wastewater
Accuracy; Calibration method; On-line measurement; Robustness; Sensor; Water quality