Regulating endogenous orthophosphate to initiate a synchronous short-pass nitrification and denitrification phosphorus removal granular sludge process
LI Dong1, XIE Yi-bo1, GAO Fei-yan1, ZHU Yan-jun1, ZHANG Jie1,2
1. Beijing Key Laboratory of Water Quality Science and Water Environment Restoration Project, Beijing University of Technology, Beijing 100124, China; 2. State Key Laboratory of Urban Water Resources and Water Environment, Harbin University of Technology, Harbin 150090, China
Abstract:Orthophosphate is an intermediate product of the biological denitrification process of phosphorus aggregation, which affects the activity of denitrifying phosphorus aggregating bacteria (DPAOs) in competition with other heterotrophic bacteria for carbon sources. In this study, four groups of sequencing batch reactors (SBRs) were operated with various endogenous orthophosphate regulating techniques utilizing synthetic water as influent after being inoculated with flocculent activated sludge.The study aimed to investigate the effects of different endogenous orthophosphate regulation methods on the enrichment of denitrifying phosphorus accumulating bacteria (DPAOs) and granulation. The results showed that the granular sludge operated with endogenous orthophosphate effluent reflux exhibited better nitrogen and phosphorus removal efficiency, higher DPAO activity, and good particle sedimentation performance.In particular, compared to granular sludge systems operated in microaerobic mode, those operated in anaerobic/microaerobic (AO) mode demonstrated superior pollutant treatment performance, with COD, TN, and TP removal efficiencies reaching 92.57%, 94.7%, and 97.62%, respectively. This was attributed to multiple factors, such as endogenous orthophosphate stimulation, the synergistic effect of DPAOs and denitrifying glycans bacteria (DGAOs).Periodic regulation of endogenous orthophosphate in the system resulted in a significant increase in the internal carbon source conversion rate of sludge, enhanced activities of DPAOs and DGAOs, and inhibition of heterotrophic denitrifying bacteria (DOHOs). Under a longer cycle operation mode, ammonia oxidizing bacteria (AOB) and DPAOs interacted, while also inhibiting the growth of other heterotrophic microorganisms. The findings of this study provide theoretical support for the practical engineering application of simultaneous short-range nitritation-denitritation phosphorus removal (SPNDPR) process.
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