Influence of changes of the wastewater composition on the applicability of UV-absorption measurements at combined sewer overflows.

The applicability of UV-absorption measurements at combined sewer overflows was investigated under different storm water conditions. Three specific rainfall events of different intensity, different duration and different intervals between the events were investigated. An individual evaluation of each single event resulted in an acceptable correlation between the UV absorption and the pollution measured as COD. A combined evaluation of the different events exhibited a very poor correlation which could not be used as pollution control parameter. Since the calibration procedure of the spectrometer used was not flexible enough to distinguish between different wastewater matrices from the different storm events the applicability of this type of spectrometer for the control of storm water overflows is questionable.