Novel composite gel beads for the immobilization of ammonia-oxidizing bacteria: Fabrication, characterization, and biokinetic analysis

Novel composite gel beads that entrap ammonia-oxidizing bacteria (AOB) were developed for wastewater treatment. The AOB-entrapping composite gel beads, which were monodispersed and millimeter-sized, were produced by a method that combined suspension-gelation with sedimentation polymerization. This method involves the preparation of calcium alginate microcapsules, which contain AOB, by electrostatic atomization and free radical polymerization of droplets of a pre-gel aqueous suspension containing microcapsules during their descent into silicone oil. AOB-entrapping non-porous gel beads, without the microcapsules, were also prepared as a control. The AOB entrapped in both the composite and non-porous gels were grown in a continuous stirred tank reactor fed with synthetic inorganic nitrogenous wastewater. The AOB-entrapping gels successfully catalyzed ammonia oxidation. The kinetics of the reaction were analyzed using the Haldane model with inhibition by a substrate.