Tham khảo tài liệu 'waste water treatment and reutilization part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fungal Decolourization and Degradation of Synthetic Dyes Some Chemical Engineering Aspects 79 liquid oxygen transfer heat transfer and mixing as well as the chemical reactions in a liquid phase like oxygen and substrate consumption the biomass growth and enzyme production take place simultaneously during the cultivation. On the basis of regime analysis it must be established which of the above mentioned processes is the slowest and therefore controls the microbial growth and enzyme production. During the transfer from the laboratory to larger scale an optimization of this process must be considered. Historically keeping a constant gas-liquid oxygen transfer rate in a small and large scale was mostly used proving as a successful scale up criteria. Namely the low rate of this process compared to other previously mentioned is characterized by low oxygen solubility in water and can be improved with increased mixing and aeration. Usually the geometrical similarity of both reactors was ensured and the maximum allowed impeller tip speed to avoid cell damage was taken into account. According to the above mentioned a general scale up criteria for the microbial cultivation is to keep the optimal environmental conditions as much as possible on all scales to obtain the necessary productivity Wang et al. 1979 . The dye degradation and or decolourization reactions at a given enzyme activity in the solution take place in a liquid phase and do not depend on oxygen gas-liquid mass transfer. According to the literature data these reactions are mostly slow. The scale up of this process needs the expression of the reaction rate at a given dye concentration range as well as the optimal pH and temperature. On the basis of the reactor type its operation mode rate equation and given dye conversion the necessary degradation time in a large batch reactor of a given volume can be estimated. Similarly the dye feed rate in a large continuous reactor can be calculated cf. Equations 3-5 . In the
