Method Establishment And Experimental Study Of Cycle Dynamic Backwashing

Cycle dynamic backwashing is proposed, which is based on the research status of media backwashing and its core is to load airlift on backwash and construct new air-water backwashing system. The influence of different factors on the media backwashing is investigated by experiments to lay the foundation for further study of dynamic backwashing media mechanism.Factors affecting the filtering effect are selected and the influence of individual factors on the removal of oil and suspended solids in water is investigated by single factor experiment,it shows that the filtering effect is the best when the particle size is 0.6~0.8mm and the thickness of the filter is 1.2m. The influence of different levels of particle size, thickness and filtration rate on the removal efficiency of suspended solids and oil is investigated by orthogonal test, the results show that the order of the influence on oil removal efficiency is particle size, filtration rate and filter thickness, while the order of the effect on suspension solids is particle diameter, filter thickness and filtration rate. The optimal structure of filter layer is, filter size of 0.6~0.8mm, filter thickness of 0.8m, filtration rate of 8m/h. The continuity equation of filtration which is based on conservation of mass is established, and calculates the expression of filtration precision.The experimental model of cycle backwashing is established, which is based on airlift theory and air-water backwashing theory to explore the influence of the backwashing rates on media regeneration. The order of the influence on cycle dynamic backwashing is air wash intensity, water wash intensity and washing time, which is determined by orthogonal test. The optimum backwashing parameters is: the water wash intensity is 10.0L/s.m2, the air wash intensity is 10.5L/s.m2 、 washing time is 15 min. The regenerating effect of filter under optimum conditions and the filtering efect of regenerational filter is investigated by experiments.The concept of critical fluidization is proposed and the minimum fluidization velocity gradient is calculated.