Study on the Modified triphenyl tetrazolium chloride – dehydrogenase activity (TTC-DHA) Method in Determination of bioactivity in the up-flow aerated bio-activated carbon filter

Abstract

The study applied triphenyl tetrazolium chloride-dehydrogenase activity (TTC-DHA) method to detect the activities of attached biofilm on bio-activated carbon (BAC) samples in the up-flow aerated biological activated carbon filter (UABACF) treating textile secondary effluent. Modification to the conventional TTC-DHA determination method was proposed. In the modification, BAC samples were used directly to measure TTC-DHA without pre-separating the attached biofilm from carbon samples. After modification, the mean values of biofilm TTC-DHA activities for the BAC samples at different heights of the biofilter were 25 to 193 times higher than those measured in conventional way. In addition, the microbial activity distribution related more closely to substrate removal along the height of the reactor after modification. The results indicated that high activity of the bacteria that are firmly fixed on the porous surface of the media would be ignored during pre-separation of the attached biofilm from media surface. The study also indicated the influence of granular activated carbon (GAC) adsorption on the bio-activity of attached biofilm. GAC adsorption was favorable in the improvement of the activities within the biofilter, especially when the attached films were destroyed. The modification of TTC-DHA determination method made this technique more convenient and accurate in activity measurement of biofilm fixed on porous surface structured activated carbon. Keywords: Up-flow, aerated bio-filter, BAC, TTC-DHA, bioactivity