Role of hydrocyclone separator on the formation and separation of aerobic granular sludge: Evaluating granulation efficiency and simulating hydrodynamic behavior

Recently, hydrocyclone separator is introduced into the field of aerobic granular sludge (AGS), and applied in wastewater treatment plant to recover the dense sludge. However, the function of hydrocyclone separator for AGS cultivation is still unclear. Thus, the granulating and granular separation efficiencies of hydrocyclone separator were investigated from perspectives of experiment and hydrodynamic modelling. By comparing traditional sequencing batch reactor, the introduction of hydrocyclone separator greatly decreased the mixed liquid suspended sludge by maximum 61%, although it could improve the sludge settling performance and reduce SVI, no matter operational time of separator high or low. The reason might be attributed to strong shear force and centrifugal force provided by hydrocyclone separator. Therefore, the inlet water velocity, a factor of shear stress, was studied. The medium water velocity of 0.3 m/s contributed to appropriate tangential velocity and static pressure, reaching the optimal granular separation efficiency that was larger than 97% for the particle diameter over 400 mu m. Besides, carrier particles in previous studies were summarized and found to enhance AGS formation in short time (15 to 54 days). When they were combined with hydrocyclone separator for continuous AGS cultivation, the carrier particles with large particle size (GAC, ceramsite, etc) were proposed to be used, instead of biochar or graphite oxide nanoparticle. This study explored the feasibility of hydrocyclone separator to culture AGS, which is helpful to realize the continuous AGS cultivation.

Automated summary

This study investigated the application of a hydrocyclone separator in the field of aerobic granular sludge (AGS). The granulating and granular separation efficiencies of the hydrocyclone separator were studied through experiments and simulations. The results showed that the hydrocyclone separator significantly reduced the suspended sludge in the mixed liquid, improved sludge settling performance, and reduced SVI. The optimal granular separation efficiency was achieved at a specific water velocity. Additionally, the use of carrier particles with larger particle size was suggested to enhance AGS formation.