Experimental Study And Numerical Simulation On Disintegration Of Excess Sludge With Fluid Shear Force And Ultrasonic Cavitation Combined

The activated sludge process is currently the most widely used for sewage treatment technologies international, but its biggest drawback is that it can produce a surprising amount of excess sludge while treating sewage, improper handling will have caused great harm to the environment. Find the suitable sludge treatment methods which become the urgent problem of modern sewage treatment technology.Minimization and recycling of excess sludge is currently a hot research issue of Environmental Science and Engineering. Reusing organic matter in the excess sludge and reduction of sludge production is the development direction of the sludge treatment. Although the disintegration of sludge is an important means to achieve sludge reduction and resources, but high energy consumption has been a major constraint on the reasons that disintegration is not universal. We propose a combination of ultrasonic and mechanical joint disintegration of excess activated sludge process, trying to combine the advantages of mechanical and ultrasound to achieve reasonable energy consumption of the most effective crack excess sludge. This topic using the U.S. imports high-speed tissue crusher and domestic probe adjustable ultrasonic instrument on the activated sludge, made a series of comparative experiment. According to the experimental result data, I can determine the proper process parameters to disintegrate the excess activated sludge. Use CFD (Computational Fluid Dynamics) software FLUENT (ie the tissue crusher in this subjectl) to simulate the process of disintegration of the activated sludge with mechanical method, and confirmed activated sludge was driven by the high-speed rotating blades in the container to form a violent turbulence in the entire container large enough to produce fluid shear stress, makes the microorganisms cell walls into fragmentation, organic matter released from the cells. The fluid shear stress determines the level of the sludge cracked-out rate.The results show that:the setting parameters of the ultrasound and mechanical break time are the key factor in decision of sludge cracking rate. When the ultrasonic of20kHz,600W disintegrated activated sludge for5minutes firstly, and then break activated sludge with tissue crusher at speed of24000rpm for7minutes, the breaking efficiency of activated sludge, is highest. Since then, input more energy, sludge crack effect was slight.