Evaluation of INT-electron transport system activity and OUR tests for heavy metal inhibition of activated sludge

摘要

The sensitivities of INT-electron transport system activity and OUR tests to Cu_(2+), Zn_(2+), Cd_(2+), Hg_(2+), Ni_(2+), Pb_(2+) and Ag_+ and the inhibition of the two tests and COD removal rate under heavy metal toxicity were compared to evaluate both the tests for assessing heavy metal inhibition of activated sludge. The median inhibitory concentrations (IC50s) of the seven tested heavy metals measured via OUR test were lower than those measured via INT test, which indicates that the INT-electron transport system activity test was less sensitive to heavy metal toxicity than the OUR test. Tested heavy metals brought about similar decrease in OUR and COD removal rate, but less decrease in INT-electron transport system activity than COD removal rate, which suggests that the OUR is a better parameter for reflecting heavy metal inhibition of activated sludge than INT-electron transport system activity. The ranking of tested heavy metals in order of decreasing toxicity based on INT test was Hg~(2+), Ag~+, Cu~(2+), Cd~(2+), Zn~(2+), Ni~(2+) and Pb~(2+), and the ranking based on OUR test was Hg~(2+), Cu~(2+), Ag~+, Cd~(2+), Zn~(2+), Ni~(2+) and Pb~(2+).