Optimal low-frequency mechanical vibration enhances extracellular polymeric substances-mediated phosphorus removal in biological systems
The biological phosphorus removal (BPR) process relies on frequent phosphorus exchange between functional microorganisms and their surrounding environment. However, limited mass transfer restricts the overall phosphorus removal efficiency. In this study, low-frequency mechanical vibration (LFMV) was introduced into the anaerobic/oxic (A/O) reactors. The results indicated that LFMV at 40 Hz significantly improved biological phosphorus removal performance. Assessment of the mass transfer coefficient and sludge characterization collectively demonstrated that optimal LFMV effectively enhanced mass transfer efficiency, primarily due to alterations in physicochemical properties (e.g., particle size, surface charge, and functional groups). Further analysis of phosphorus distribution and extracellular polymeric substances (EPS) composition suggested that LFMV improved EPS-mediated phosphorus adsorption and storage by modifying EPS content and composition. Moreover, quantification of metabolism-related biological activities (i.e., specific metabolic rate and metabolic enzyme activities) revealed that optimal LFMV accelerated phosphorus transformation within EPS. In addition, the ³¹P NMR spectra confirmed that LFMV facilitated orthophosphate transport in loosely bound EPS (LB-EPS) and promoted the interconversion between orthophosphate and polyphosphate in tightly bound EPS (TB-EPS). These findings collectively indicate that optimal LFMV (i.e., 40 Hz) effectively accelerates phosphorus removal by enhancing EPS-related adsorption, storage, and transformation processes. This study provides a promising technical strategy for improving efficiency and promoting energy conservation in biological phosphorus removal systems.
The biological phosphorus removal (BPR) process relies on frequent phosphorus exchange between functional microorganisms and their surrounding environment. However, limited mass transfer restricts the overall phosphorus removal efficiency. In this study, low-frequency mechanical vibration (LFMV) was introduced into the anaerobic/oxic (A/O) reactors. The results indicated that LFMV at 40 Hz significantly improved biological phosphorus removal performance. Assessment of the mass transfer coefficient and sludge characterization collectively demonstrated that optimal LFMV effectively enhanced mass transfer efficiency, primarily due to alterations in physicochemical properties (e.g., particle size, surface charge, and functional groups). Further analysis of phosphorus distribution and extracellular polymeric substances (EPS) composition suggested that LFMV improved EPS-mediated phosphorus adsorption and storage by modifying EPS content and composition. Moreover, quantification of metabolism-related biological activities (i.e., specific metabolic rate and metabolic enzyme activities) revealed that optimal LFMV accelerated phosphorus transformation within EPS. In addition, the ³¹P NMR spectra confirmed that LFMV facilitated orthophosphate transport in loosely bound EPS (LB-EPS) and promoted the interconversion between orthophosphate and polyphosphate in tightly bound EPS (TB-EPS). These findings collectively indicate that optimal LFMV (i.e., 40 Hz) effectively accelerates phosphorus removal by enhancing EPS-related adsorption, storage, and transformation processes. This study provides a promising technical strategy for improving efficiency and promoting energy conservation in biological phosphorus removal systems.