Studies on the preparation of immobilized-cell membrane and its characteristics

Abstract

The nitrifying bacteria and denitrifying bacteria were coimmobilized with polyvinyl alcohol (PVA) and the immobilized-cell membrane was prepared by circulatory freezing and thawing method. The effects of the carrier concentration and the number of times of freezing-thawing on the membrane strength, the diffusion coefficient of substrate in the membrane, and the activity of the immobilized-cell were investigated. At the same time, a new bioreactor for biodenitrification and matched with the immobilized-cell membrane was designed, and the operational stability of the immobilized-cell membrane was investigated. The results showed that the PVA membrane prepared at PVA concentration of 13%(w/w) and 15%(w/w), and the freezing-thawing number of times of about 5 possessed higher strength and activity of the immobilized-cell was also higher. When the freezing-thawing number of times and PVA concentration were 5 and 15%(w/w) respectively, the maximum tensile stress and the diffusion coefficient of ammonia nitrogen in PVA membrane were 1.52MPa and 0.75 × 10 -9 m 2/s respectively. The immobilized-cell membrane remained stable both in its form and cell activity for a period of 2 months operation.