Two packed bed column (PB) systems, namely anoxic-anoxic and anoxic-oxic were investigated for treatment of wastewater containing high concentrations of nitrogen (N) and COD. The anoxic-anoxic PB system was able to achieve N and COD removal rates of up to 6.70 kg N/m3.d and 26.02 kg COD/m3.d, respectively. The responding removal rates of the anoxic-oxic PB system were 7.41 kg N/m3 and 28.00 kg COD/m3.d, respectively. The N and COD removal efficiencies of anoxic anoxic PB system were in the range of 99.2-100% and 97.2-98.8%, respectively. The corresponding removal efficiencies of anoxic-oxic PB system were 97.5-100% and 98.6-99.4%, respectively. These findings showed that a PB system consisting of anoxic-oxic columns in series has a high capacity to remove nitrogenous and carbonaceous compounds even though the influent to the anoxic stage was oxygenated. Better system stability in terms of denitrification was, however, obtained with the anoxic-anoxic system.

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