The anaerobic treatment of nitrite containing wastewater using an expandedgranular sludge bed (EGSB) reactor

The integration of denitrification from nitrite with methanogenesis was stu died in this work. Experimental results from the continuous treatment of wa stewater containing nitrite, which lasted for 144 days, demonstrated that w astewater containing nitrite could be anaerobically treated in an expanded granular sludge bed (EGSB) reactor. From 92% to 97% of COD was removed at o rganic COD volumetric loading rates up to 6.5 g COD l(-1) d(-1). Nitrite wa s denitrified for 97% to 100% at nitrite volumetric loading rates up to 0.9 g NO2--N l(-1) d'. Batch tests of 15 days with sludge from the reactor sho wed that 100% of nitrite and 93 to 95% of COD were removed. Nitrite was den itrified for 92 to 96% to N-2. The remaining nitrite might be converted to NO and N2O. The ratio of COD to NO2--N for the denitrification was varied f rom 2.49 to 5.64. Denitrification from nitrite preceded methanogenesis. Met hanogenesis recovered rapidly after the denitrification from nitrite was co mpleted. No dissimilatory reduction of nitrite to ammonium occurred. Some s mall losses of ammonium could not be accounted for in the process.