ABSTRACT
The purpose of the combined Powdered activated carbon (PAC) activated sludge treatment process is to adsorb a great part of the phenols by the PAC in order to lower their load on the biomass. The PAC modifies the process and affects its general performance not only through its effect on inhibitory substances, but also by sharing the total organic load with the biomass. In case of refinery wastewater the PAC activated sludge combined process involves three simultaneous mechanisms of removal; namely, stripping, adsorption on PAC, and biological degradation. The chapter provides a better understanding of organic removal mechanisms acting in a PAC-activated sludge process, treating concentrated wastewater of an integrated oil refinery. An important part of the organics, 40%, were removed by stripping. Organics unremoved by stripping could be classified into three categories: adsorbed on PAC, most of them phenols; removed by biodegradation; and residual in effluent, most of them nonbiodegradable.
