An activated sludge-based biosensor for rapid IC50 estimation and on-line toxicity monitoring.

The RODTOX (Rapid Oxygen Demand and TOXicity tester), an activated sludge-based respirographic biosensor, is a device for on-line monitoring of the short-term biochemical oxygen demand (stBOD) and potential toxicity of incoming wastewater on the basis of on-line interpretation of respirograms resulting from pulse additions of either calibration substrate or sample. The principle of toxicity detection is based on the comparison of calibration respirograms before and after receiving a potential toxicant. In this paper, the results of the RODTOX as an on-line toxicity monitor are presented. In addition, a simple and fast procedure to estimate the IC50 of a toxicant has been developed, and its validity and good repeatability demonstrated. The performance of this procedure is compared with that of the Microtox test.