Cultivation of aerobic granules and substances degradation kinetics at low temperature

Abstract:

The aerobic granules (AGS) were difficult to cultivate and the degradation kinetics of AGS at low temperature were seldom investigated, which greatly limited the development and application of AGS. In this study, AGS possessed better settling property and higher biomass after cultivation by sodium acetate for 25 d, furthermore, AGS formation time significantly decreased for 48 d at 10 ℃ in a sequencing batch airlift reactor (SBAR) and AGS possessed better simultaneously COD, NH₄+-N and PO₄3--P removal efficiency at low temperature, and the respective removal efficiencies were 845％, 911％ and 941％. Compared with the conventional cultivation of AGS, the content of total protein was as high as 1061 mg／g and the total proteins／total polysaccharides (m(PN)／m(PS)) ratio was 157, which meant that the relative high protein content was an essential feature for AGS formation. The adsorption of organic substances by AGS was higher than that of floc sludge because of the higher contents of EPS, more channels for mass and oxygen transfer as well as the greater specific surface area of AGS. The experimental data indicated that the substances degradation kinetics generally followed Monod equation, the corresponding kinetic coefficient of k and Ks were 549 d-1 and 4 760 mg／L, respectively. The degradation rate of substances was obviously influenced by the mass transfer efficiency between liquid phase and AGS.