Determination of dissolved oxygen limitation in aerobic biofilm reactors

✍ Scribed by Guang Hao Chen; Wun Jern Ng; Hiroaki Ozaki; Yutaka Terashima

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 402 KB
• Volume: 11
• Category: Article
• ISSN: 0921-3449
• DOI: 10.1016/0921-3449(94)90079-5

✦ Synopsis

The concentration of dissolved oxygen (DO) strongly influences the performance of aerobic biofilm reactors because organic oxidation is limited by the availability of oxygen. However, it is not necessary to maintain a high DO level in the reactors in order to overcome this limitation. Excessive aeration wastes energy. Therefore, the determination of the onset of DO limitation against organic substrate removal in aerobic biofilm reactors is important for their effective operation. This study is aimed at developing an expression to determine the onset of DO limitation and hence to control the aeration system. The expression developed is as follows: Cb < Rb" (Dws/Dwc)'Sb, where Sb and CD are the bulk concentrations of organic substrate and DO, respectively; Dws and Dwc are the diffusion coefficients of organic substrate and oxygen in the reactors respectively; and Rb is an overall ratio of oxygen consumption to organic substrate removal in the reactors. The latter is the key parameter in the equation, and is determined by the characteristics of the substrate, biofilm, and reactor. In order to measure the value of Rb, the authors have developed a micro-biofilm reactor. The value of Rb was determined to be 0.13 (mg 02 mg-l CODer) for glucose removal with this reactor. The equation has, subsequently, been verifed with data from batch and continuous experiments.

ABBREVIATIONS

Cb

Concentration of DO in bulk liquid phase (mg 02 L-1 ) Cf Concentration of DO within biofilm (mg 02 L-~ ) Cs Concentration of DO on biofilm surface (mg 02 L-1 ) Dfc Diffusion coefficient of oxygen within biofilm (cm 2 d-l ) Dfs Diffusion coefficient of organic substrate within biofilm (cm 2 d-t ) Dwc Diffusion coefficient of oxygen in bulk liquid phase (cm 2 d-1 ) Dws Diffusion coefficient of organic substrate in bulk liquid phase (cm 2 d-~ ) Da Diffusion coefficient electron acceptor in bulk liquid phase (cm 2 d-l ) Dd Diffusion coefficient electron donor in bulk liquid phase (cm 2 d-1 )