Since the oxygen consumption is directly associated with the growth and respiration of biomass, the respirometry has been widely used in estimating the efficiency and stability of an activated sludge process. Thus, in this study, organic oxidation, nitrification and denitrification, the main steps in the biological nitrogen removal process, were monitored using the respirometry. The results were also simulated using ASM No. 1 calibrated with biomass and substrate concentrations.
The monitoring results showed that the respiration rates were dependent on the biomass and substrate concentrations. Besides, the simulation results showed good agreements with respiration rates in nitrification and denitrification. However, there were some gaps in the simulation result of organic oxidation due to the simplification of complex organic matters into two fractions. In the model calibration, the organic fractions of wastewater were determined to be about 16%, 38%, 4%, 22% and 20 % for $S_S$, $X_S$, $S_I$, $X_I$ and $X_H$, respectively. The active heterotrophic and autotrophic biomass fractions were about 12 % and 3.6 %, respectively, in VSS concentration of sludge. In denitrification, the specific denitrification rates were 1.07, 1.54 and 0.39 mg-N/VSS/h for $S_S$, $X_S$ and endogenous respiration, respectively.
It was thought that the respirometry could be used for the understanding the organic and ammonia oxidation processes and the ASM No. 1 could be used for the simulation of those oxidation processes.
