Novel Sidestream Enhanced Biological Phosphorus Removal System for Highly Efficient Nitrogen and Phosphorus Removal: Performance, Microorganisms and Mechanisms

This study introduces a novel sidestream enhanced biological phosphorus removal (S2EBPR) system, which was successfully operated for two hundred and three days. Unlike previous systems, this approach facilitated effective cooperation between Candidatus Accumulibacter, Dechloromonas, and sidestream fermentation microorganisms, eliminating the need for Tetrasphaera in phosphorus removal. In the two-stage operation, removal efficiencies for COD and PO4 3- P increased from seventy-three point seven percent and seventy-five point three percent to eighty-three point two percent and ninety-one point eight percent, respectively. The system exhibited significant biological activity, with peak phosphorus release reaching forty-nine point three milligrams per liter in a typical cycle, marking a sixty-six percent improvement compared to Phase I. 16S rRNA gene amplicon sequencing revealed successful enrichment of functional microorganisms, with Candidatus Accumulibacter and Dechloromonas reaching twelve point nine percent and six point two percent in the mainstream reactor, respectively. Additionally, key genes (ugpQ, ppk1, phnC) and enzymes (polyphosphate kinase, adenylate kinase) associated with phosphorus removal were enriched. Overall, the novel S2EBPR system demonstrated stable operation, with Candidatus Accumulibacter and Dechloromonas as the primary enriched phosphorus-accumulating organisms, successfully collaborating with fermentative microbes.