No abstract

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 suspended‐growth batch reactor was used to denitrify synthetic wastewater containing various proportions of nitrate and nitrite. A competitive phenomenon between nitrate‐ and nitrite‐reductase was studied utilizing various proportions of nitrate and nitrite in an anaerobic environment with a temperature of 30°C and methanol as carbon source. By using a non‐linear regression technique, biokinetic constants of the maximum specific reduction rates of nitrate and nitrite (k1, k2) and the Monod half‐saturation coefficients of nitrate and nitrite (Ks1, Ks2) for the proposed two‐step denitrifying kinetics were 1·29 day−1, 0·89 day−1 and 14·3 mg NO 3−‐N dm−3, 10.9 mg NO 2−‐N dm−3, respectively. The result obtained from a series of chemostat studies indicated the Monod‐type kinetic model was more accurate when the distributed ratio of nitrate‐ and nitrite‐reductase in the proposed two‐step denitrifying kinetics was taken into account.