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A granular activated carbon- powdered activated carbon technology- shortcut biological nitrogen removal combined system (GAC-PACT-SBNR) was developed to enhance total nitrogen (TN) removal for the anaerobically treated coal gasification wastewater (CGW) with less external carbon resource. The TN removal efficiency in SBNR was significantly improved via introducing the effluent from GAC process into SBNR during anoxic stage, with percentage increasing from 43.8%-49.6% to 68.8%-75.8%. But the TN removal rate decreased with the progressive deterioration of GAC adsorption. After adding activated sludge into GAC compartment, the granular carbons had a longer service-life and the demand for external carbon resource became lower. Eventually, TN removal rate in SBNR was almost constant at approx. 43.3% as compared to approx. 20.0% before seeding sludge. Besides, the production of some alkalinity during the denitrification resulted in a net savings in alkalinity requirements for the nitrification reaction and refractory COD degradation by autotrophic bacteria in SBNR under oxic condition. PACT showed excellent resilience to the increasing organic loadings. The microbial community analysis revealed that the PACT had a greater variety of bacterial taxons and the dominant species associated with 3 compartments were in good agreement with typical pollutants removal. The study demonstrated the pre-adsorption by GAC-sludge process could be a technically and economically feasible method to enhance TN removal of CGW.
