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Denitritification and denitratification in anoxic filters were performed to generate experimental data. Also, a kinetic model of denitratification that accounts for intrinsic biokinetics and hydrodynamic behavior of the biofilter is proposed. In denitritification, the simulated results are in good agreement with the experimental data; and a higher nitrite influent concentration gives a higher nitrite reduction efficiency if the denitrifying loading is kept the same. In denitratification, the intermediate nitrite tends to accumulate, and a higher denitrifying loading results in a higher nitrite effluent concentration. By inserting biological and physical parameter values into the kinetic model, the variations in distributed fractions of nitrate‐reductase (f) and nitrite‐reductase (1‐f) with different denitrifying loadings can be estimated by fitting in experimental data. The estimated f increased with an increase in denitrifying loading, implying that a higher denitrifying loading results in a higher nitrite effluent concentration. From parametric sensitivity analyses, the parameter f is more sensitive than other biological and physical parameters. Accordingly, the proposed kinetic model of denitratification can be used to predict the treatment performance of anoxic filters appropriately. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:52–61, 1998.

A kinetic model that accounts for the distributed fraction of methanogens (f) and granule-size distribution of upflow anaerobic sludge bed (UASB) reactors is proposed. In addition, the anaerobic degradation of phenol in four UASB reactors with various superficial flow velocity (u s ϭ 0.5, 1.0, 2.0, and 4.0 m/h) was performed to generate experimental data. When using the proposed kinetic model, the calculated residual concentrations of phenol, volatile fatty acids, and chemical oxygen demand are in fairly good agreement with the experimental data. With an increase in either u s or volumetric loading, the granule size of the UASB reactor increases. The experimental f values decrease with an increase in volumetric loading; the f values in the lower and middle part of the sludge bed tend to be larger than those in the upper part of the sludge bed. Water Environ. Res., 75, 5 (2003).