Responses of Biological Activated Carbon to Shock Loadings of Wastewater Qualities.

Parallel studies using biological activated carbon (BAC) and sand with bioactivity were conducted to evaluate the response of BAC to changes of substrate inflow. Low molecular weight substances with different biodegradability and adsorbability, i.e, 2,4-dichlorophenol (2,4-DCP), phenol, glucose, were fed into BAC and sand reactors. The influent substrate was changed from glucose to phenol (I), from phenol to glucose (II), and from 2,4-DCP to glucose and back to 2,4-DCP (III). In case of (I), effluent DOC concentration in the sand reactor increased temporarily by the change in influent substrate, because acclimation time was necessary for the new substrate. However, the BAC reactor removed the new substrate without any lag time because the new substrate was removed by adsorption. In case of (II), BAC reactor showed better performance than the sand reactor after the change in influent substrate, however, effluent DOC concentration in the BAC reactor also increased. The difference in the BAC performance between (I) and (II) was due to the different adsorbability of the new substrates, i.e, phenol with high adsorbability easily adsorbed on BAC after the change influent substrate from glucose to phenol and glucose with low adsorbability could hardly adsorb on BAC after the change influent from phenol to glucose. The change in influent substrate from 2,4-DCP to glucose (III) made the effluent DOC concentration increase in both reactors and the biodegradation to glucose in the BAC reactor delayed in comparison with sand reactor. Because 2,4-DCP has high adsorbability and desorbability, desorbed 2,4-DCP inhibited biodegradation of glucose after the change in influent substrate. Re-inflow of 2,4-DCP in day 12 did not increase effluent DOC concentration, because 2,4-DCP has high adsorbability and BAC kept biodegradability to 2,4-DCP by biodegradation of the desorbed 2,4-DCP during inflow of glucose.