Comparison between INT and TTC assay to determine the dehydrogenase activity of flocs

In order to evaluate the efficiency of anaerobic activated sludge in hydrogen-producing system, iodonitrotetrazolium chloride (INT) and triphenyl tetrazolium (TTC) assay were optimized for detecting the specific dehydrogenase activity of the flocs. The results showed that both INT and TTC assay under the optimum conditions could be used to determine dehydrogenase activity. In comparison with TTC assay, INT assay was more sensitive and precise. In the range between 3.5-12.5 g/L of sludge concentration (MLVSS), the INT assay are 2.8 mL reactant, 0.3 mL sludge sample, 1 mL 19.8 μmol/L INT solution, pH 5.0, an oscillating reaction at 45°C for 30 min, anhydrous ethanol as the extraction solvent and wavelength of 478 nm. The correlation coefficient between specific dehydrogenase activity and specific hydrogen production rate, R, was above 0.93, excellently reflecting the hydrogen-producing activity of flocs.