A comparative study of microbial dynamics and phosphorus removal for a two side-stream wastewater treatment processes

In this study, a side-stream process with anoxic/aerobic tanks was designed as a denitrifying enhanced biological phosphorus removal wastewater treatment technology (denitrifying EBPR) to be evaluated for its performance in phosphorous (P) removal as compared to a modified side-stream process using contact/stabilization tanks (modified EBPR). Under variable P and ammonia–nitrogen loadings, the microbial community structure, dominant taxonomy, and community dynamics were assessed with the aid of real-time PCR analysis and MiSeq high-throughput sequencing aimed specifically at the major polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs). The inclusion of an anoxic tank for the denitrifying EBPR process increased the efficiency of P removal by reducing the amount of nitrate entering the anaerobic tank, which led to increased P removal of 67.9–78.6% compared to 35.2–68.4% for the modified EBPR under various P and ammonia loading conditions. PCR analysis showed that the increased P removal performance of the denitrifying EBPR under increased ammonia loading may be attributed to higher abundances of PAO clade I organisms. MiSeq sequencing analysis indicated that the influent water composition played an important role in the microbial community structure; however, there was an increase in genetic differences between the two systems under high ammonia and P loadings. Overall, Dechloromonas and Sphingomonas were the dominant PAOs and GAOs in both systems. The denitrifying EBPR process resulted in increased concentrations of PAOs versus GAOs as compared to the modified EBPR which resulted in the improved performance of this process.