Effect of Influent COD/N Ratio on Nitrification Rate in a Bench-scale Biological Reactor

Document Type : Research Paper


1 Associate Professors of public Health, Isfahan University of Medical Sciences

2 Faculty Member of public Health, Lorestan University of Medical Sciences


Nitrification, the oxidation of ammonia to nitrate catalyzed by bacteria, is a key part of the global nitrogen cycle. In the first step of nitrification, chemolithoautotrophic ammonia oxidizers transform ammonia to nitrite, which subsequently oxidizes to nitrate by nitrite-oxidizing bacteria. This process can be affected by several factors. In this study, the effect of influent COD/N ratio on nitrification rate in a bench-scale biological reactor was investigated. Experiments were carried out using synthetic wastewater. The initial ammonium concentration was 25 mg NH-N L1. The effect of COD/N ratio between 10.010.083 and 24.080.22 gCODgN-1 on nitrification rate was investigated by varying the COD loading supplied to the reactor. From the results obtained, it may be concluded that in the range of 10.010.083 to 14.150.17 gCODgN-1, a direct relationship holds between COD/N ratio and nitrification rate. However, an indirect relationship holds between COD/N ratio and nitrification rate at ratios above 14.150.17 up to 24.080.22 gCODgN-1.


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