Sedimentation monitoring of the active biomass in bioreactors by electrical impedance spectroscopy

Sequencing batch reactors are used in wastewater treatment to produce biogas (methane). Currently, when biogas production ceases the active sludge sedimentation process is not monitored but operated on a fixed time basis. One step towards gas production optimization would be to detect sedimentation and no expend time unnecessarily. In this work the use of electrical impedance spectroscopy is explored as a tool for sedimentation monitoring. Two electrodes were placed vertically on the reactor wall and the impedance measurements were used to compute the impedance estimator E
2
. Changes in E
2
have proven to be reliable enough to detect whenever the active sludge fell below the lower electrode position hence enabling the development of impedance probes to monitor sedimentation for this kind of reactors.