tailieunhanh - Wastewater Purification: Aerobic Granulation in Sequencing Batch Reactors - Chapter 2

Cắt lực lượng từ thủy lực và / hoặc va chạm hạt hạt đã được coi là một trong những yếu tố ảnh hưởng đến hầu hết trong cấu trúc, hình thành, và sự ổn định của màng sinh học (van Loosdrecht et al 1995; Y. Liu và 2001a Tây, năm 2002). Một cao hơn cắt lực lượng sẽ cho kết quả trong một màng sinh học mạnh mẽ hơn và nhỏ gọn, trong khi màng sinh học có xu hướng trở thành một cấu trúc xốp không đồng nhất, và yếu hơn khi các lực trượt yếu (Chang và cộng sự năm 1991; van. | 2 Aerobic Granulation at Different Shear Forces Qi-Shan Liu and Yu Liu CONTENTS Aerobic Granulation at Different Shear Effect of Shear Force on Granule Effect of Shear Force on Granule Effect of Shear Force on Biomass Effect of Shear Force on the Production of Cell Effect of Shear Force on Cell References . 35 INTRODUCTION Shear force resulting from hydraulics and or particle-particle collision has been considered as one of the most influencing factors in the formation structure and stability of biofilms van Loosdrecht et al. 1995 Y. Liu and Tay 2001a 2002 . A higher shear force would result in a stronger and compact biofilm whereas biofilm tends to become a heterogeneous porous and weaker structure when the shear force is weak Chang et al. 1991 van Loosdrecht et al. 1995 Chen Zhang and Bott 1998 . It has been shown that biofilm density increases with the increase of shear stress while biofilm thickness exhibits a decreasing trend Chang et al. 1991 Ohashi and Harada 1994 Kwok et al. 1998 . Biofilm density correlates very closely with the selfimmobilization strength of fixed bacteria which is determined by the shear force imposed on the biofilms Ohashi and Harada 1994 Chen Zhang and Bott 1998 . It appears that a certain shear force in the biofilm system is necessary in order to produce a compact and stable biofilm structure that is higher shear force favors the formation of a smoother and denser biofilm. In anaerobic granulation it has been observed that granulation proceeded well at relatively high hydrodynamic shear condition in terms of high upflow liquid velocity whereas anaerobic granulation was absent at a weak hydrodynamic shear force Alphenaar Visser and Lettinga 1993 OFlaherty et al. 1997 Alves et al. 2000 . These seem to indicate that shear force may also play an important role in the anaerobic granulation