Study On The Influence Of Floc Morphology On Sedimentation Performance In Grid Flocculation Tank

The paper adopts a grid flocculation tank model as the experimental flocculation tank,and selects experimental parameters based on pre experiments for single factor variable experiments.By changing a single variable for flocculation experiments,real-time images of the flocculation process and static settling process are obtained.Image analysis software is used to calculate parameters such as floc area,perimeter,particle size,quantity,and floc settling speed in the floc image.The effects of various operating conditions on floc morphology,floc effluent quality,and floc settling performance are studied,and the following conclusions are drawn:1.During the flocculation process of grid flocculation tank,low flow rates at the same mesh size are more likely to aggregate and form loose large particle size flocs.At low flow rates at the same position,the particle size is higher than other pore flow rates.As the pore flow rate increases,the particle size of the flocs formed gradually decreases and the number of flocs is greater than that of other pore flow rates.The influence of pore flow rate on the average particle size is greater than that of mesh size.The higher through-hole flow rate,due to its short flocculation time and strong eddy current strength,causes loose flocs to break into dense small flocs.The appropriate through-hole flow rate can balance the particle size and density of the flocs.The floc Fractal dimension is the largest when the flow rate through the pore is 10.18 cm/s,and the sedimentation performance is higher than that of other flow rates through the pore;2.During the flocculation process of the grid flocculation tank,at the same flow rate,the floc particle size generated by the 10 mm mesh size in the grid flocculation tank is larger than that generated by the other mesh sizes.The floc generated by the 10 mm mesh size shows a higher fractal dimension compared to the other three mesh sizes,and the floc generated by the 10 mm mesh size shows a lower number of flocs;3.The static sedimentation water quality of the flocculated effluent from the grid flocculation tank is tested.When the mesh size is 10 mm and the through-hole flow rate is13.40 cm/s,it has a lower residual turbidity and a higher turbidity removal rate.According to the multi-angle analysis of the flocs under various working conditions in the paper,when the mesh size is 10 mm and the flow rate of the through hole is 13.40 cm/s,more colloidal particles aggregate into dense large particle flocs,and the flocculated water exhibits better settling performance;4.When the grid flocculation tank flocculates and settles the effluent,the average particle size of the 10 mm mesh floc is the smallest and the number of flocs is the smallest among the four types of mesh size flocculent effluent settling process.At 13.40 cm/s,the average particle size of the flocs is relatively low,and at a flow rate of 10.18 cm/s through the pores,the number of flocs after settling is generally lower than other flow rates through the pores.The size of the mesh has a greater impact on the turbidity removal rate than the flow rate of the through hole,but the flow rate of the through hole has a greater impact on the settling speed of the floc than the size of the mesh.