Evaluation of Granular Activated Carbon and an Activated Sludge for the Treatment of a Chemical Industry Refractory Wastewater

This research compared contaminant removal from a thermophilic aerobic bioreactor effluent in an activated sludge system and granular activated carbon (GAC) system. Adsorption isotherms indicated that the adsorbability of the thermophilic effluent at low dissolved organic carbon (DOC) concentrations is much greater than the activated sludge effluent, while the effective diffusivity of DOC in the activated sludge system was approximately 30% greater than the thermophilic on GAC. The effluent DOC concentrations from the pilot activated sludge system were not only in line with the existing full scale GAC system, but also were less affected by drastic fluctuations in the thermophilic DOC effluent. Irrespective of the various operational conditions, the thermophilic effluent contained around 200 mg/l of refractory and/or slowly biodegradable DOC, as well as 100 mg/l of non-adsorbable DOC. A cost comparison showed that there is significant savings if the activated sludge system were to be implemented with an estimated simple payback period of 2.6 years as compared to the existing GAC system.