Surveying an activated sludge reactor using online UV-visible and NIR spectroscopy and chemometrics

Abstract

The performance of activated sludge reactors can be enhanced by the ability to monitor the status of the process without the need for chemicals addition or complex calibration procedures. Nowadays automation is still limited by poor sensor performance and high maintenance costs. Spectroscopic methods associated with chemometrics are being presented as a powerful tool for process monitoring and control. Once implemented, the method is fast, non-destructive and it can be implemented online, permitting to rapidly infer about the status of the process being monitored. In this work, UV-Visible and Near Infra-Red (NIR) Spectroscopy were used to monitor an activated sludge reactor using immersion probes that were connected to the respective spectrophotometers using optical fibbers. During the monitoring period, changes were induced in the system to test the ability of the monitoring scheme to detect them. The results obtained so far show that it is possible to clearly detect changes in the influent composition as well as the effects of a sudden increase in the influent flow which are among the most common problems that can disturb a biological WWT system. The use of the NIR range for this application is not as common as the UV-Visible range and a direct comparison will allow taking conclusions about the advantages and/or disadvantages of one compared to the other.