Research On The Physical And Biological Clogging Development In The Packed Bed During Water Treatment

During the engineering practice of water treatment based on the filter,it is gradually found that clogging is a common problem in packed bed,which greatly restricts the application and popularization of this technology.Physical and biological clogging are the main types of blockage in the packing bed.Hence,in this paper,we firstly studied the physical clogging,then discussed the distribution of the pollutants and clogging mechanism by using XCT scanning techniques.Next,we studied the law of biological clogging at different organic load.Further,we chose different water distribution to observe the effect of organic load and microorganism.The main contents in this paper are as follows:(1)In order to study the physical clogging,several vertical flow model devices respectively with zeolite,gravel or glass beads were established by making up artificial sewage.Based on the research of the model unit,the result shows that the suspended solid load has an exponential relationship with permeability coefficient in clogging.Meanwhile the packing type,filler particle size and suspended particle size have influence on physical clogging.The X-ray scanning of industrial computed tomography shows that when the particle size is small,the migration of suspended solids in packed bed includes three periods:puncture phase for the pollutants?the formation of the blanket-like deposition layer?the formation and compaction phase to the whole clogging layer.When the size of the filler is large,the suspended matter is less affected by pore throat,and will continue migrating down and precipitating.(2)To invesgate the mechanism of physical clogging,this paper analyzed the distribution of suspended matter in the packing chamber based on the preliminary experiment,and summarized the threshold of the device of particle penetration test.The result shows that the suspended matter is mainly concentrated in the upper part of the packing layer,and the depth is exponential distribution.In the filter with zeolite,when dss/dfs is larger than 130,or dss/dfs/ass is more than 120,the suspended matter will penetrate the experimental device.In the gravel filter,when dss/dfs is larger than 8,or dss/dfs/ass is more than 10,the suspended matter will penetrate the experimental device.(3)Several multiple vertical flow model devices with gold sand as packed bed were established in this paper in order to study the variation law of permeability coefficient in filling chamber.The results show that the effect of biological activities on the permeability coefficient is greater than the effect on porosity,and the decline of permeability coefficient is mainly above the middle part in the filler.