Research On Raw Water From Jialing River By Spiral Lamellar Sedimentation

Sedimentation which is used to remove suspended substances is the main unit in conventional water treatment process. As a result research the performance of precipitation and enhancing its removal ability can further reduce the effluent turbidity and improve water quality. By comparing a variety of sedimentation methods, the ramp plate (tube) sedimentation is a highly effective precipitation separation method and it has been widely used in the treatment process. However when it is applied to a small-scale, all-in-one, water-treatment plant, the existence of dead zone is inevitable during installation process due to influence of dimension of the device. In addition the proportion of dead zone is relatively high, especially for a circular device.In order to solve this deficiency of traditional ramp (tube) sedimentation method, a new ramp - spiral ramp is designed to adapt to the circular device in this dissertation. The space utilization rate for this ramp can reach 100% without no "dead zone". At the same height of precipitation zone, the spiral ramp can have larger precipitation area contribution to high dewatering efficiency. Mechanical mixing flocculation experiments were designed and applied to Jialing River raw water so as to investigate performances of the new ramp. Experimental results indicate that the suitability of the spiral ramp is quite strong and water quality of the effluent is stable.Three different coagulants----polyaluminium chloride, polyacrylamide and ferric chloride and different quantities of coagulants were tested in experiments. The results shows that: when the influent turbidity is around 100NTU , the best dosage for aluminum chloride (PAC) is 15 mg / L respectively. Removal rate of turbidity and UV254 is optimal. In winter when the influent turbidity is around 10NTU, the best dosage for aluminum chloride (PAC) and ferric chloride (Fecl3) is 10 mg / L and of 15 mg / L respectively. Removal rate of turbidity and UV254 is optimal.Three types mixtures-concrete mixture, muddy water,sandy water and water are used as mediators to simulate density distrubtion and veloctiy distrubtion of flow field so as to get distrubtion condition of precipitation zone. These further work are done by Fluent software.And it is considered free setting in sedimentation area,but no considering of collision and coalescence amang fluid inner.Finally feasibility analysis of applicability of the spiral ramp sedimentation method to the western town carried out both in economy and technology parts shows that this technology is feasible, has economic advantages and is suitable for small towns in the Three Gorges reservoir area.