2025 Volume 111 Issue 2 Pages 41-50
The coke-oven wastewater contains high concentrations of ammonia, COD (chemical oxygen demand) and toxic compounds such as phenols, cyanides, and thiocyanate. This wastewater is one of the most toxic industrial wastewater. Although the activated sludge process has been applied to treatment of the coke-oven wastewater, the treatment was occasionally deteriorated by inhibition of toxic compounds. Especially, the nitrification step was sensitive to toxic compounds, nitrite (NO2−) was often accumulated due to incomplete nitrification. Nitrite is toxic and has a negative effect on COD degrading bacteria. The complete nitrification was required for stable treatment.
In this study, aiming at simultaneous removal of ammonia and COD from the coke-oven wastewater, a bench-scale nitrification/denitrification plant was operated. By long-term acclimation and the addition of an iron source, the complete nitrification was stably occurred for about 8 months, and a nitrogen removal efficiency of nearly 70% was achieved. In addition, COD in the influent was consumed as an organic source for denitrification, and the addition of an organic source was able to be minimized.
