The aerobic biofilm on naphthalene as the carbon source: Growth, biodegradability, and mass transfer-diffusion kinetics

Stable biofilm formation and substrate loss during mass transfer are key factors affecting the treatment efficiency of biofilm systems. In this research, a comprehensive study was conducted on the growth, biodegradability and mass transfer process of Ochrobactrum anthropi Na-B biofilm. The results showed that the biofilm mass increased at different rates before tending to stabilize under the optimal conditions. The growth process was divided into six phases and the biofilm which in logarithmic phase showed the highest microbial activity and the best degradation performance, the average removal of 30 mg/L naphthalene reached 61% after 24 h under pH= 7.0, T = 30 degrees C, and r = 100 rpm. With the growth and maturation of biofilm, microcolonies began to form on the membrane carrier surface and finally presented a dense, continuous and three-dimensional reticular biofilm structure. Furthermore, the mass transfer performance of biofilm declined with the growth of biofilm, the increase of initial naphthalene concentration and the decrease of temperature. The Mass Transfer-Diffusion kinetics of biofilm further indicated that in the range of 5-30 mg/L naphthalene concentration, the internal diffusion resistance in the biofilm was negligible and the mass transfer process of biofilm was mainly restricted by the external mass transfer resistance and biological reaction.