Excess phosphorus in water supplies causes eutrophication, which degrades water quality. Hence, the efficient removal of phosphorus from wastewater represents a highly desirable process. Here, we evaluated the effect of sulfate concentration on enhanced biological phosphorus removal (EBPR), in which phosphorus is typically removed under anaerobic-oxic cycles, with sulfate reduction the predominant process in the anaerobic phase. Two sequencing batch EBPR reactors operated under high- (SBR-H) vs. low-sulfate (SBR-L) concentrations for 189 days and under three periods, i.e., start-up, sufficient acetate, and limited acetate. Under acetate-rich conditions, phosphorus removal efficiency was > 90% for both reactors; however, under acetate-limited conditions, only 34% and 91.3% of the phosphorus were removed for the SBR-L and the SBR-H, respectively. Metagenomic sequencing of the reactors showed that the relative abundance of the polyphosphate-accumulating and sulfur-reducing bacteria (SRB) was higher in the SBR-H, consistent with its higher phosphorus removal activity. Ten high-quality metagenome-assembled genomes, including one closely related to the genus Thiothrix disciformis (99.81% average amino acid identity), were recovered and predicted to simultaneously metabolize phosphorus and sulfur by the presence of phosphorus (ppk, ppx, pst, and pit) and sulfur (sul, sox, dsr, sqr, apr, cys, and sat) metabolism marker genes. The omics-based analysis provided a holistic view of the microbial ecosystem in the EBPR process and revealed that SRB and Thiothrix play key roles in the presence of high sulfate.

Key points

• We observed high phosphorus-removal efficiency in high-sulfate EBPR.

• Metagenome-based analysis revealed sulfate-related metabolic mechanisms in EBPR.

• SRB and PAOs showed interrelationships in the EBPR–sulfur systems.

Graphical abstract

中文翻译：

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硫酸盐对增强生物除磷作用的元基因组学见解

供水中过量的磷会引起富营养化，从而降低水质。因此，从废水中有效去除磷代表了非常理想的过程。在这里，我们评估了硫酸盐浓度对增强的生物除磷（EBPR）的影响，其中磷通常在厌氧-有氧循环下被去除，而硫酸盐的还原是厌氧阶段的主要过程。两个测序批量EBPR反应器在高（SBR-H）与低硫酸盐（SBR-L）浓度下运行189天，并在三个时期内运行，即启动，充足的乙酸盐和有限的乙酸盐。在富含乙酸盐的条件下，两个反应器的除磷效率均大于90％。然而，在乙酸盐限制的条件下，对于SBR-L和SBR-H，仅分别去除了34％和91.3％的磷。反应器的元基因组测序表明，SBR-H中聚磷酸盐积累和还原硫细菌（SRB）的相对丰度更高，与其较高的除磷活性一致。十个高质量的元基因组组装基因组，其中一个与属密切相关圆盘拟南芥（平均氨基酸身份达99.81％）被回收并预测通过磷（ppk，ppx，pst和pit）和硫（sul，sox，dsr，sqr，apr，cys）的存在同时代谢磷和硫和sat）代谢标记基因。基于组学的分析提供了EBPR过程中微生物生态系统的整体视图，并揭示了在存在高硫酸盐的情况下SRB和硫代丝虫起着关键作用。

关键点

•我们观察到高硫酸盐EBPR的除磷效率很高。

•基于基因组的分析揭示了EBPR中硫酸盐相关的代谢机制。

• SRB和PAO在EBPR-硫系统中显示出相互关系。

图形概要