Ammonia-oxidizing bacterial community and nitrification rates in constructed wetlands treating swine wastewater

The goal of this study was to investigate the correlation between the potential nitrification (PN) rate and ammonia-oxidizing bacteria (AOB) in wetlands treated with swine wastewater. The wetlands showed high efficiency in the removal of NH4+, NO3-, and chemical oxygen demand (COD). Nitrification and denitrification occurred concurrently in the wetlands. The most probable number (MPN) value of AOB was highly related to NH4+ (R-2 = 0.92, P<0.05) and NO3- concentrations (R-2 = 0.96, P<0.05), but not significantly correlated with COD. The AOB Shannon-Weaver diversity index (H) and richness (S) which were calculated from digitalized profiles of denaturing gradient gel electrophoresis (DGGE) did not correlate with NH4+ and NO3- concentrations. The PN rates in detritus and soil samples highly correlated with NH4+ (R-2=0.92, P<0.5). The phylogenetic trees based on 16S rRNA gene sequences and amino-acid-residue sequences of the amoA gene showed that parts of the AOB from the wetlands were affiliated with beta-proteobacteria cluster 2, cluster 6a, cluster 7, and Nitrosospira sp. NSP65. (c) 2011 Elsevier B.V. All rights reserved.