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Wastewater Purification: Aerobic Granulation in Sequencing Batch Reactors - Chapter 6

Tham khảo tài liệu 'wastewater purification: aerobic granulation in sequencing batch reactors - chapter 6', khoa học tự nhiên, công nghệ môi trường phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 6 Selection Pressure Theory for Aerobic Granulation in Sequencing Batch Reactors Yu Liu and Zhi-Wu Wang CONTENTS 6.1 Introduction.85 6.2 Is Aerobic Granulation Inducible .86 6.3 Earlier Understanding of Aerobic Granulation.86 6.4 Brief Review of Parameters Contributing to Aerobic Granulation.87 6.4.1 Substrate Composition and Loading.88 6.4.2 Hydrodynamic Shear Force.88 6.4.3 Feast-Famine Regimen.89 6.4.4 Feeding Strategy.89 6.4.5 Dissolved Oxygen.89 6.4.6 Reactor Configuration.90 6.4.7 Solids Retention Time.90 6.4.8 Cycle Time. 90 6.4.9 Settling Time . 91 6.4.10 Exchange Ratio.92 6.4.11 Discharge Time. 92 6.5 Main Selection Pressures of Aerobic Granulation.92 6.6 A Selection Pressure Theory for Aerobic Granulation in SBRs.93 6.7 Failure of Aerobic Granulation in Continuous Microbial Culture.97 6.8 Upscaling Aerobic Granular Sludge SBRs.100 6.9 Prediction of Settling Velocity of Bioparticles.102 6.10 Conclusion. 107 References.107 6.1 INTRODUCTION It appears from the preceding chapters that almost all research on aerobic granulation has been conducted in sequencing batch reactors SBRs while no successful aerobic granulation has been observed in continuous microbial culture. As shown in chapter 5 it is believed that aerobic granules form through self-immobilization of 85 2008 by Taylor Francis Group LLC 86 Wastewater Purification bacteria when suitable selection pressure is provided in the SBR. Compared to continuous microbial culture the unique feature of an SBR is its ability to be operated in a cyclic mode and a cycle of SBR for aerobic granulation may comprise filling aeration settling and sludge discharge. A number of parameters have been known to influence the properties of aerobic granules formed in SBRs. Basically contributing parameters include substrate composition organic loading hydrodynamic shear force feast-famine regimen feeding strategy dissolved oxygen reactor configuration solids retention time cycle time settling time and volume exchange ratio .