Biosensors for the measurement of toxicity of wastewaters to activated sludge

When wastewaters from chemical manufacturing are discharged for biological treatment it is important to ensure that the presence of potentially toxic chemicals is below concentrations that may impair the performance of the treatment plant. This report describes the use of mediated amperometric biosensors incorporating activated sludge to provide rapid determination of toxicity in wastewaters to activated‐sludge‐based water‐treatment plants. Redox‐mediated interrogation of the microbial consortium comprising the biosensor biocatalyst allowed real‐time monitoring of metabolic activity and the detection of perturbation due to toxic challenge. A time‐independent inhibition value was determined within 30 min of exposure, using a mathematical model based on a hyperbolic relationship between exposure time and biosensor inhibition. Comparative testing of the biosensors and an activated sludge respiration inhibition test (ASRIT) against 35 wastewater samples, from a wide variety of industrial discharges, showed the close correlation coefficient of 0·924 between the two test methods. © 1998 Society of Chemical Industry