Evaluating Quantitative PCR Assays to Enumerate Several Bacterial Populations of Importance in Different Municipal Wastewater Treatment Designs

This study evaluated the efficacy of quantitative polymerase chain reaction (qPCR) to monitor several pertinent bacterial populations in 25 different full-scale wastewater treatment bioreactors across 9 different system designs. All the bioreactors contained a substantial quantity of total bacterial biomass and denitrifying bacteria, independent of system design. In contrast, the quantities of ammonia oxidizing bacteria (AOB) and phosphate accumulating organisms (PAOs) measured by qPCR targeting the amoA gene and the 16S rRNA genes, respectively, from the Candidatus Accumulibacter lineage significantly correlated with system design. Bioreactors with short mean cell residence time (<2 days) had significantly lower AOB abundance than most of the other bioreactors (all pairwise comparisons P<0.0001, except for a membrane-coupled bioreactor). Similarly, bioreactors designed for enhanced biological phosphorus removal had significantly higher relative quantities of PAOs than did conventional systems (P<10-18). In conclusion, these qPCR assays should be practically useful for monitoring full-scale wastewater treatment bioreactors, thereby helping to improve process performance.