VALIDITY OF THE TTC-TEST FOR DEHYDROGENASE-ACTIVITY OF ACTIVATED SLUDGES IN THE PRESENCE OF CHEMICAL INHIBITORS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 169  (3-4) , 320-330
Abstract
Dehydrogenase activity of activated sludges [a measure of biological treatment plant performance] coming from a laboratory plant was evaluated by the TTC[2,3,5-triphenyl tetrazolium chloride]-test in the presence of some toxic chemicals. The results showed that, for all inhibitors tested, there existed a range of concentrations in which the dose-response relationship was linear. As far as the comparison of the inhibition data from the TTC-test and from the O2 respiration rate is concerned, the results obtained show that the inhibitors tested may be divided into 3 groups: inhibitors which inhibit the O2-respiration rate more than the dehydrogenase activity (Zn2+, Cd2+, Ni2+, Hg2+, Zn(CN)42-, Cd(CN)42-); inhibitors for which there are no significant differences in the inhibition value obtained by the 2 methods (CN-, C6H5O-, C6Cl5O-, C6H3ClO-, Hg(CN)42-) and inhibitors which inhibit the dehydrogenase activity more than the O2 respiration rate (Cu2+, CrO42-, Ni(CN)42-). The inhibition data obtained by evaluating by direct methods (COD [chemical O2 demand] reduction, turbidity of the final effluent, etc.) the performance of pilot or laboratory plants in the presence of some of the toxics were in sufficient agreement with this dehydrogenase inhibition data.