Structural integrity affects nitrogen removal activity of granules in semi-continuous reactors
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Updated: Apr 24, 2026

A Novel Bioreactor for High Density Cultivation of Diverse Microbial Communities
Published on: December 25, 2015
Cesar R Mota1, Melanie A Head, Jon C Williams
1Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, NC, 27695, USA, cesar@desa.ufmg.br.
Abstract:
Granules were observed after more than two years of operation in two semi-continuously fed intermittently aerated reactors treating swine wastewater with aerobic:anoxic cycles of 1:1 h and 1:4 h. Subsequently, the granules and flocs were compared with respect to physical characteristics, activity, and microbial community structure. Granules exhibited higher specific nitrification and denitrification rates than flocs. However, once granule structural integrity was disrupted, the rates decreased to levels similar to those of flocs. Membrane hybridizations using 16S rRNA-targeted probes showed that ammonia oxidizing bacteria populations in flocs and granules were dominated by Nitrosomonas and Nitrosococcus mobilis. Granules provided better conditions for Nitrospira compared to flocs. The diversities of the dominant bacterial populations in granules and flocs were not significantly different. Our findings highlight the importance of structural integrity of granules to their nitrogen removing activity.
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