Co‐immobilized Nitrosomonas europaea and Nitrobacter agilis cells: validation of a dynamic model for simultaneous substrate conversion and growth in κ‐carrageenan gel beads

Abstract

A dynamic model for two microbial species immobilized in a gel matrix is presented and validated with experiments. The model characterizes the nitrification of ammonia with Nitrosomonas europaea and Nitrobacter agilis co-immobilized in K-carrageenan gel beads. The model consists of kinetic equations for the microorganisms and mass transfer equations for the substrates and products inside and outside the gel beads. The model predicts reactor bulk concentrations together with the substrate consumption rate, product formation, and biomass growth inside the gel beads as a function of time. A 50-day experiment with immobilized cells in a 3.3-dm(3) air-lift loop reactor was carried out to validate the model. The parameter values for the model were obtained from literature and separate experiments. The experimentally determined reactor bulk concentrations and the biomass distribution of the two microorganisms in the gel beads were well predicted by the model. A sensitivity analysis of the model for the given initial values indicated the most relevant parameters to be the maximum specific growth rate of the microorganisms, the diffusion coefficient of oxygen, and the radius of the beads. The dynamic model provides a useful tool for further study and possible control of the nitrification process. (c) 1994 John Wiley & Sons, Inc.

Methane Oxidation and the Competition for Oxygen in the Rice Rhizosphere

“…Rate constants for ammonia, thiosulfate, and ferrous iron were much smaller than those found for overall oxidation. Nitrifiers have a low potential growth rate (34), which might explain the low rate constant found for NH 4 ϩ oxidation. Microbial thiosulfate oxidation was also much lower than overall thiosulfate oxidation, which is in contrast to what has been found by Stubner et al (56).…”

Dynamics of artificially immobilizedNitrosomonas europaea: Effect of biomass decay

“…The dynamic model evaluated in this study is based on the model of Hunik et al (1994). except that N. europaea is the only microbial species present in the gel bead.…”

“…We determined the two decay rates in the absence of oxygen or ammonium and incorporated these values in the model as described by Hunik et al (1994).…”

“…Treatment systems need to be designed in such a way that fluctuations in for example water temperature and substrate loadings have no significant negative effect on the effluent quality. Growth of immobilized cells has been studied extensively, and dynamic models were developed describing the immobilized-cell process Dos Santos et al, 1996;Hunik et al, 1994;Monbouquette et al, 1990;Wijffels et al, 1991Wijffels et al, , 1995Willaert, 1996). The effect of changes in temperature has been described previously (Leenen et al, , 1996, and in the study presented here, the effect of biomass decay was investigated.…”

Distribution of Nitrosomonas europaea and Paracoccus denitrificans Immobilized in Tubular Polymeric Gel for Nitrogen Removal

“…For example, bioreactors used for wastewater treatment include a biofilm containing bacterial cells fixed onto carriers (2,9,10,27,30) or gel beads (6,12,14,18,19). In such arrangements, only the surfaces of the carriers or beads have activity, because substrates and oxygen for the immobilized cells are supplied only from the surface (11,16,17,23,25,31).…”