污水处理毕业论文英文翻译.doc

BIODEGRADABILITY AND CHANGE OF PHYSICAL CHARACTERISTICS OF PARTICLES DURING ANAEROBIC DIGESTION OF DOMESTIC SEWAGE Abstract: At the high-rate anaerobic treatment of domestic sewage, both biological and physical processes play an important role. Therefore, the anaerobic biodegradability of raw, paper-filtered and membrane-filtered sewage and black water has been investigated in batch experiments. Additionally, the effect of anaerobic digestion on physical characteristics, like particle size, surface tension and zeta-potential, of the present particles is studied. The biodegradability of domestic sewage and black water at 308C is almost similar (71?74%). Moreover, a high methanogenesis of the colloidal fraction in domestic sewage (86_3%) is achieved, showing that the low removal of colloidal particles in continuous high-rate anaerobic reactors is due to low physical removal rather than biodegradability. The lowest biodegradability is demonstrated for the dissolved fraction (62%). The results show that after anaerobic digestion the average radius of particles with diameter54.4 and50.45 mm increased for domestic sewage, while it decreased for black water. Part of the surface-active components in domestic sewage is not biodegraded during anaerobic batch digestion, as indicated by the development of the surface tension. The negative zeta-potential of all particles hardly changes during digestion, showing that colloidal interactions were not affected by anaerobic digestion. Key words: anaerobic treatment, domestic sewage, black water, biodegradability, particle size, surfactants, zeta-potential INTRODUCTION Several authors have shown that particles represent the major part, up to 85%, of the total COD (CODt) in domestic sewage (Levine et al., 1985; Zeeman et al., 1997). The separation of particulate and dissolved compounds in domestic sewage is usually made by filtration through a membrane filter with a pore diameter of approximately 0.45 mm (Nielsen and Harremoes, 19