DIN 38412-3:2010-10

Microorganisms contain enzymes (biocatalysts), which cause degradation of the constituents present in waste water. One group of these enzymes are dehydrogenases; they cleave hydrogen atoms from the substances (waste water constituents). The more dehydrogenases contained in activated sludge, the more active the sludge. According to this method, triphenylformazan (TPF) is produced from triphenyl tetrazolium chloride (TTC) in the activated sludge through the dehydrogenase activity of the living cells. As there is no dehydrogenase activity once the cells are dead, the presence and the quantity of produced TPF is a measure for the sludge activity. This standard specifies a method for the estimation of the acute inhibitory effect of a test object on mainly heterotrophic bacteria from activated sludge of municipal and/or industrial wastewater treatment plants. The inhibitory effect is determined after an incubation period of 1 h. The method is applicable to waste water and non-volatile water-soluble chemical substances. Insolubles can also be detected, if special care is taken that the test mixture is homogeneous. The method does not only allow the determination of toxic effects, but also the quantitative determination of the biochemical activity of the inoculum. The standard has been prepared by Working Group NA 119-01-03-05-08 AK "TTC-Test" ("TTC-Test") of Working Committee NA 119-01-03 AA "Wasseruntersuchung" ("Water Analysis") and been funded by Länderfinanzierungsprogramm "Wasser, Boden und Abfall" (federal funding programme "Water, soil and waste").