A sequence of unit processes consisting of a berl-saddle-packed anaerobic filter, an expanded-bed, granular activated carbon anaerobic reactor and an activated sludge nitrification system was employed for the treatment of synthetically prepared coal gasification wastewater. After acclimation, the coal gasification wastewater was fed to the treatment process train at three different chemical oxygen demand levels; these were 1,513. 3,027, and 7,567 mg/ℓ, respectively. No biological activity was observed in the first-stage filter, while excellent removal of organic matter was achieved in the second and third stages of the treatment systems. However, toxicity to the anaerobic culture in the second-stage reactor was observed during the second and third loading levels. This toxicity was overcome by employing a partial replacement schedule of the granular activated carbon medium in the reactor. This study represents an example of how biodegradation and physical adsorption may be successfully combined during the treatment of wastewaters containing toxic or inhibitory substances.

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