A submersible UV/VIS spectrometer for in-situ real-time measurements is presented. It utilises the UV/VIS range (200-750 nm) for simultaneous measurement of COD, filtered COD, TSS and nitrate with just a single instrument. A global calibration is provided that is valid for typical municipal wastewater compositions. Usually high correlation coefficients can be achieved using this standard setting. By running a local calibration improvements concerning trueness, precision and long term stability of the results can be achieved. The calibration model is built by means of PLS, various validation procedures and outlier tests to reach both high correlation quality and robustness. This paper describes the UV/VIS spectrometer and the calibration procedure.

a measure for the presence of organic compounds (Conio et. al., 2002). Through analysis of the entire spectrum of UV and visible light, however, a lot of the entire UV/Vis region was only possible using expensive equipment, suited only for operation in a well controlled laboratory environment. As the first online instruments for use in the field have now reached the market, it is time to determine the use and capabilities of these instruments. 1.Abstract. The UV-absorption of water at 254 nanometer has often been used as 1,*