Study On The Modeling On Filtration Of Microtubule Self-Forming Dynamic Membrane And Control Strategy

As a promising new sewage treatment technology, the dynamic membrane bioreactor has some important advantages:high membrane flux, low cost filter material, low energy requirement and high anti-pollution capacity. But there are still some shortcomings which limit the acceptance of dynamic membrane bioreactor in the wastewater treatment, including the unstable flux and incomplete membrane backwashing. According to its unique operation procedure, a self-adaptive dynamic membrane (SADM) was designed. The performance with a high flux, the flow field simulation and mathematical model of the self-adaptive dynamic membrane were investigated. The main contents and results are as follows:The performance of membrane modules with different materials in submerged bioreactor were compared. The performance of the SADM in recirculated bioreactor was also investigated. The results demonstrated that the SADM had the best performance:the membrane flux reached up to 60L/m2h; the stable operation time reached up to 480.3 h; the membrane formed in less than 1min.The microbial communities of activated sludge with 42μm～50μm and 150μm-200μm particle size were identified by the Miseq High-throughput sequencing technologies. There exists no obvious difference between the microbial community diversity between activated sludge with different particle sizes. The same predominant phyla included Proteobacteria, Actinobacteria and Bacteroidetes. The genus with great difference were Zoogloea, Anaeromyxobacter and Geobacter.Three-dimensional computational fluid dynamics models for submerged bioreactor and recirculated membrane module were built to compared their flow fields. The flow field of recirculated membrane module are uniform and the velocity near the membrane surface is 0～0.003m/s. Meanwhile, the flow field of recirculated membrane module are not uniform and the velocity near the membrane surface is 0～0.05m/s, which made its performance inferior to the recirculated membrane module.The structure characteristics development of the cake layers were investigated by various analytical methods, including Brunauer-Ernrnett-Teller (BET) nitrogen adsorption, scanning electron microcopy and EPS analysis. The membrane resistance was highly correlated with the membrane thickness and the polysaccharide concentration of the T-EPS. The compression of the cake layer with time was not observed. The porosity and specific surface area declined in the initial 12 hours, due to the disappearance of the small diameter pores (1-10 nm) with time. The porosity and specific surface area were also found to decline from the top layer to the bottom layer, due to the blockage of large diameter pores (30-250 nm).The CASADM was modified to describe the reactions in the DMBR. The MLSS composition, the SCOD composition, the net sludge yield and the methane production rate in each tank were analyzed.A pilot scale test lasting for 12 months was conducted to evaluate the long-term applicability of the self-adaptive membrane module. The effluent COD, TP, NH3-N and SS as well the turbidity concentrations were similar to or even below the values achieved in the traditional wastewater treatment plants. A simple economic comparison with activated sludge system and MBR was made. The control strategy of the dynamic membrane bioreactor was summarized, according to the pilot scale test and bench scale test.Current results provided an important data for the industrialization and producibility of the self-forming dynamic membranes.