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Up-to-date, nghiên cứu chuyên sâu đã được dành riêng cho tác động của điều hành khác nhau các thông số về hạt hiếu khí trong trình tự các lò phản ứng hạt nhân hàng loạt (SBRs) (chương 1 đến 7). Tuy nhiên, rất hạn chế thông tin hiện có về sự khuếch tán hành vi của các chất bên trong hạt hiếu khí. Tây et al. (2002) thấy rằng một mô hình thuốc nhuộm chỉ có thể thâm nhập vào 800 mm dưới bề mặt của hạt hiếu khí, trong khi Jang et al. (2003) đã báo cáo độ sâu thâm nhập của 700 micromet. | 8 Diffusion of Substrate and Oxygen in Aerobic Granules Yong Li Zhi-Wu Wang and Yu Liu CONTENTS 8.1 Introduction.131 8.2 Size-Dependent Kinetic Behaviors of Aerobic Granules.132 8.3 Description of Diffusion Resistance in Aerobic Granules.133 8.4 Simulation of Mass Transfer in Aerobic Granules.135 8.4.1 Model Development.136 8.4.2 Substrate Profile in Aerobic Granules with Different Radiuses.139 8.4.3 Oxygen Profiles in Aerobic Granules with Different Radiuses.139 8.4.4 Diffusion Profiles of Substrate in Aerobic Granules at Different Bulk Substrate Concentrations.139 8.4.5 Diffusion Profiles of Dissolved Oxygen in Aerobic Granules at Different Substrate Concentrations.141 8.4.6 Prediction of Bulk Substrate Concentration in an Aerobic Granules Reactor.143 8.5 Conclusions.144 Symbols.145 References.146 8.1 INTRODUCTION Up-to-date intensive research has been dedicated to the effect of various operating parameters on aerobic granulation in sequencing batch reactors SBRs chapters 1 to 7 . However very limited information is currently available about the diffusion behaviors of substances inside aerobic granules. Tay et al. 2002 found that a model dye was only able to penetrate 800 pm beneath the surface of aerobic granules while Jang et al. 2003 reported a penetration depth of 700 pm for dissolved oxygen from the surface of aerobic granules. Meanwhile oxygen diffusion limitation in nitrifying aerobic granules was detected by microelectrode Wilen Gapes and Keller 2004 . Moreover the unbalanced microbial growth inside aerobic granules has been supposed to be due to the mass diffusion limitation in aerobic granules which would further lead to a heterogeneous internal structure see chapter 11 . These indicate 131 2008 by Taylor Francis Group LLC 132 Wastewater Purification that without a proper control of the mass diffusion the structural stability of aerobic granules might not be sustainable. In view of the importance of substrate and oxygen in microbial culture this chapter
