A Ferricyanide-mediated Activated Sludge Bioassay for Determination of the Toxicity of Water

Activated sludge was successfully exploited as the medium in the fast ferricyanide‐mediated toxicity (FM‐TOX) bioassay. The mediated biosensor toxicity assessment using activated sludge greatly simplified the testing process and improved detection sensitivity. The principle of the method is that the respiration of bacteria in the activated sludge is inhibited by the pollutants, and the extent of the inhibition is related to the concentration of toxicants. A series of experimental conditions (activated sludge concentration, incubation time, reaction temperature and pH of the solution) were optimized in order to increase the sensitivity. Different kinds of toxicants and natural water samples were examined under the best conditions and IC50 values of them were obtained respectively. According to the testing results, a toxicity order was given: Hg2+>Zn2+>Cd2+>Pb2+ for heavy metal ions; 3,5‐DCP>PA>Methanol for organic toxicants and Machete>DDT for pesticides. The detection limits for those pollutants are lower than the values in the national standard. These results confirmed that this sensor may serve as an early warning device for avoiding environmental pollution and affecting public health.