Abstract
Denitrifying sulfur conversion-assisted enhanced biological phosphorus removal (DS-EBPR) has recently been developed for simultaneously removing nitrogen and phosphorus from saline sewage with minimal sludge production. This novel process could potentially enable sustainable wastewater treatment. Yet, the core functional bacteria and their roles are unknown. Here, we used high-throughput 16S rRNA gene sequencing coupled with principal coordinates analysis and ANOVA with Tukey's test to unravel the spatiotemporal heterogeneity of functional bacteria and their synergetic and competitive interactions. We did not find any obvious spatial heterogeneity within the bacterial population in different size-fractionated sludge samples, but the main functional bacteria varied significantly with operation time. Thauera was enriched (9.26~13.63%) as become the core functional genus in the DS-EBPR reactors and links denitrifying phosphorus removal to sulfide oxidation. The other two functional genera were sulfate-reducing Desulfobacter (4.31~12.85%) and nitrate-reducing and sulfide-oxidizing Thiobacillus (4.79~9.92%). These bacteria cooperated in the DS-EBPR process: Desulfobacter reduced sulfate to sulfide for utilization by Thiobacillus, while Thauera and Thiobacillus competed for nitrate and sulfide as well as Thauera and Desulfobacter competed for acetate. This study is the first to unravel the interactions among core functional bacteria in DS-EBPR, thus improving our understanding of how this removal process works.