Study On The Change Of Algae Cells Characteristics After Ultrasonic Radiation And Algae Removal Efficiency Of Enhanced Water Treatment Process

Frequent algal blooms lead to high concentrations of algae in drinking water sources,which not only reduces the efficiency of traditional coagulation and precipitation,but also increases the potential for the generation of TOC and DBPs in the effluent of water plants,which seriously affects the safety of water supply.The physical and chemical methods commonly used in the removal of algae in water plants can easily lead to the breakage or fragmentation of the algae.The escaped intracellular and algal toxins are difficult to remove in the subsequent water treatment unit,and there are potential safety risks.Ultrasonic algae removal technology has the advantages of green,environmental protection,and high efficiency,and its use in algae removal research is one of the current hot spots.Therefore,under the premise of ensuring the integrity of algae cells,it is of great significance to seek ultrasonic conditions that improve the removal of algae cells while reducing the release of organic matter.In this paper,the typical algae species(Microcystis aeruginosa and Anabaena)in the Three Gorges Reservoir area are the research objects,and the sound pressure distribution and effective distance of ultrasonic radiation in the sound field in the water are studied systematically,the effect of ultrasonic parameters and ultrasonic radiation methods on the removal efficiency,biochemical characteristics and organic release characteristics of algae cells.The main research content includes the following aspects:(1)Research on the sound field distribution and propagation characteristics of ultrasound in algae-bearing water.Use COMSOL Multiphysics,a multi-physics coupling analysis software,for numerical simulation.The simulation results show that the ultrasonic radiation frequency will affect the boundary and effective distance between the near field and the far field of the ultrasonic sound field,and the higher the frequency,the easier the energy is absorbed and the faster the attenuation.The greater the input load voltage and the higher the electric power,the greater the sound pressure generated.740 k Hz is the best frequency for algae removal in medium and high frequency ultrasonic radiation due to its high energy and relatively long effective range.(2)Research on the effect of ultrasonic parameters on the removal of algae cells and the release of organic matter.After static ultrasonic radiation,the effects of ultrasonic radiation frequency and time on the removal rate of algae cells,photosynthetic activity and organic matter release were analyzed.Research results show that the greater the frequency and duration of ultrasonic radiation,the greater the damage to algae cells,which will increase the direct removal rate of algae cells,the release of organic matter and algae toxins.The extracellular protein organic matter affects the coagulation process through various mechanisms.When the protein content is low,it can act as a flocculant to promote coagulation.As the protein content increases,it will cause adsorption saturation and adversely affect the coagulation.Through the characterization of the morphological structure of the algae cells,the effect of ultrasonic radiation on the algae cells can be visually analyzed.After ultrasonic irradiation,the folds on the surface of the algae cells were obviously deepened,and the surface was damaged.The densely packed algae cells became scattered,and fragments of the algae cells and a small amount of scattered opaque flocs appeared around,the internal structure became messy,and the central nucleus shrinks until it disappears.(3)Research on the effect of ultrasound on the flow dynamics of algae cells and process parameters.In view of the uneven energy distribution of static ultrasonic radiation due to the superposition of sound fields and the existence of ultrasonic radiation blind areas,the effect of dynamic ultrasonic radiation on algae cells was studied.Combined with the results of static ultrasound radiation,the direct removal rate of algae cells,the changes in photosynthetic activity and the release of organic matter under different ultrasound radiation methods were compared and analyzed.Under the conditions of a frequency of 740 k Hz and a power density of 0.113W/m L,dynamic ultrasonic radiation within 5 minutes can maintain the structural integrity of algae cells,which can effectively reduce the release of organic matter and algae toxins while improving the removal rate of algae cells.After dynamic ultrasound radiation,the algae cells sag and shrink inward,and there is no obvious damage on the surface,and no intracellular materials are released to the surrounding environment.The cell wall and cell membrane are damaged to a certain extent,but the cell remains intact.(4)Study on enhanced coagulation effect of ultrasonic pretreatment.After the coagulation test after ultrasonic radiation pretreatment,the coagulation effect is obviously strengthened,and the main mechanism of coagulation is adsorption bridging,net trapping and sweeping and certain electric neutralization.The ultrasonic radiation frequency is740 k Hz,the power density is 0.113W/m L,and the time is 1minute dynamic ultrasonic radiation as the pretreatment measures for the pilot test.The continuous flow pilot test of continuous operation for 4h shows that the ultrasonic radiation pretreatment can significantly improve the turbidity.The removal rate of algae cells in the precipitation unit reduces the pressure on the subsequent filtration unit;the increase in TOC removal rate and the reduction in the generation of DBPs better ensure the safety of drinking water quality.