Applications > Wastewater

Application of the ISA Spectrometer in a wastewater treatment plant

Emission limits relating to waste water are becoming increasingly important on an international level. For this reason, the determination of the concentration and composition of waste water is necessary, especially for treatment plant operators.

Therefore, certain parameters in waste water treatment plants should be observed continuously. Another important point is, that the recorded measurements are available in real time. Thereby it is possible to notice changes in concentrations and to react at once. The ISA UV/Vis Spectrometer is ideally suited for the monitoring in different areas of a treatment plants. The device allows the measurement of multiple parameters at the same time. For example, this makes it possible to simultaneously determine Ammonium, Nitrate, Nitrite and chemical oxygen demand (COD) in one single measurement.

The ISA Spektrometer can be installed in the influent, as well as the effluent of treatment plants. Moreover, the device can also be utilized in the sector of activation.

The measuring head of the spectrometer can be installed directly in to the medium to be measured. In contrast to the application of ananlysers no ultrafiltration is necessary. Therefore, sample taking or sample preparations are no longer necessary.

ISA Spektrometer

The ISA is an in situ UV/Vis absorption spectrometer, which operates in the wavelength range of 200 to 710 nm. The result of a single measurement is the absorption spectra over the entire wavelength range.

In contrast to electrochemical sensors and multi-parameter measurements, a spectrometer is a very versatile instrument. It can be adjusted by calibration to a wide variety of applications. Moreover, the ISA Spectrometer features an adjustable measuring path length. Due to this the spectrometer can be optimally adapted to a specific application area. Additionally, the device is characterized by a very low service requirement, with the special advantage that no consumables are required.

A major advantage of the ISA Spectrometer is the integrated automatic compressed air cleaning of the measuring path. For this reason the device can reach a very long operating lifetime and service intervals.

The measuring head of the spectrometer, which is made of V4A stainless steel, only houses the optics and the compressed air cleaning system. The entire control and evaluation electronics are situated in the associated sensor module or the BlueBox measuring and controlling system. As a result, the ISA Spectrometer can be used in a high temperature range (up to 110°C).

Application specific calibration

For the determination of the sought-after parameters a calibration is used, which can be optimized through the utilization of reference values. The optimization of the calibration can easily be done through the associated software ISA Calc+.

Results of a municipal waste water treatment plant

The results of the on-line measurement with the ISA Spectrometer were successfully compared with modern laboratory measurement methods. As an example the changes in concentrations of the chemical oxygen demand (COD), Ammonium and Orthophosphate in the influent of a waste water treatment plant can be examined. For the comparison between the parameters measured by the ISA Spectrometer and the reference values determined in the laboratory, a good correlation was present over the entire duration of 7 months. An accuracy of circa 5% of the measurement value was achieved.

Even during the course of seasons, accompanied by a changing water matrix, a good correlation between the spectrometer measurements and the laboratory values was reached. The stability of the calibration against changes of the matrix was further improved through the integration of additional reference values.