Evaluation of Ammonia Oxidizing Bacterial Community Structure of a Municipal Activated Sludge Plant by 454 High-Throughput Pyrosequencing

The ammonia oxidizing bacteria (AOB) community structure in a municipal wastewater treatment plant (WWTP) was monitored over the winter and summer periods. The AOB distribution in the full-scale WWTP was investigated using barcoded 454-pyrosequencing targeting the ammonia monooxygenase alpha subunit (amoA) gene. Using the quantitative polymerase chain reaction (qPCR) technique, the AOB population was quantified over 237 days. The plant operational parameters and its nitrification performance were also monitored. As revealed by pyrosequencing, majority of the identified AOB during the study were related to uncultured ammonia oxidizing bacteria, and Nitrosomonas oligotropha. Furthermore, it revealed higher AOB abundance during the summer which was 6 times more compared to winter. Substantial percentages of the reads from both seasons could not be assigned to any phylum, which suggests that vast population of novel, ecologically significant AOB species still inhabit the complex activated sludge communities unexploited. A significant seasonal variation in temperature (α = 0.05; P = < 0.0001) was recorded in the reactor with maximum temperature amplitude of 10.2 °C. The average nitrification rate recorded during the summer was 0.09 ± 0.03 g N-NH4 +/g MLSS/d, whereas it was 0.04 ± 0.02 g N-NH4 +/g MLSS/d during the winter. The nitrification rate of the plant had significant correlation with AOB population abundance (r = 0.70; P = 0.01) and temperature (α = 0.05; P = 0.0018). This study indicates that AOB diversity and population abundance were contributory factors to efficient nitrification in activated sludge system. © 2018, Springer International Publishing AG, part of Springer Nature.