| Electrochemical technology has become the research focus in water treatment because of its good treatment effect and without secondary pollution.However,the small electrochemical devices made in the laboratory have the disadvantages of small spacing,small capacity and high energy consumption,so the significance of the experimental results in the practical water treatment process was limited.This study overcame the limitation of its spacing and capacity,and took a single shaft of grid flocculation tank as the research object.To reduce the electrical energy consumption in the application of electrochemical technology,Computational fluid dynamics(CFD)was used to simulate the grid flocculation tank of a certain size,and the grid spacing was optimized based on the flocculation effect.The experimental device was made according to the numerical simulation results to investigate the removal efficiency and energy consumption of algae and humic acid in eutrophic water.The device used the grid plate of the grid flocculation tank as the cathode and the anode,and the electrode materials were all aluminum plates.First,the effect of voltage,initial pH,NaCl concentration and power time on the removal efficiency of humic acid and algae was determined by orthogonal experiment.Then,the effects of the parameters on the efficiency and energy consumption of algae and humic acid removal by grid flocculation-electrochemical technique were analyzed in detail,and the experimental conditions were optimized.Finally,the variation of water quality parameters,such as pH,electrical conductivity and dissolved oxygen(DO)in electrolysis process,were analyzed.The numerical simulation results showed that when the grid spacing was 250mm,the change of pulsating velocity in the plate area was larger,the number of micro vortex was gerater,and the effective flocculation area was reasonable.The difference between the four laminates and the two laminates were small.The setting of multi-layer plate was beneficial to improve the utilization of space and enhanced the effect of flocculation.It not only gave full play to the effect of flocculation and improved the utilization of energy,but also narrowed the spacing of the plate and reduced the cost of construction if it was used in practice.The experimental results showed that the optimum parameters of grid flocculation-electrochemical technique of humic acid wastewater treatment were as follows:the initial pH was 7~8,the concentration of sodium chloride was 3mmol/L,the voltage was 13V,and the power time was 45min.The effective volume of the device was 43L,the spacing of the plate was 250mm,and the concentration of humic acid wastewater was 7mg/L.Under the process parameters,the removal rate of humic acid could reach 83.4%,and the corresponding electric energy consumption was0.113kW·h/m~3.The pH of the solution decreased firstly and then stabilized when the initial pH was greater than 8,while it increased firstly and then stabilized when the initial pH was less than 8 under different initial pH conditions.The change of the pH in solution was within 0.5.The electrical conductivity increased slightly and then stabilized under different concentration of sodium chloride conditions.And the change of the electrical conductivity was between10us/cm and 20us/cm.When the density of algae in the log growth phase was 1.7×10~9~1.9×10~9,the optimum parameters of grid flocculation-electrochemical technique of algae containing water treatment were as follows:the initial pH was 6~7,the concentration of sodium chloride was 2mmol/L,the voltage was 13V,and the power time was 50min.Under the process parameters,the removal rate of algae could reach 89.5%,and the corresponding electric energy consumption was 0.101kW·h/m~3.Under different voltage conditions,the pH of the solution decreased firstly,then stabilized and increased lastly,while the dissolved oxygen(DO)increased firstly,then decreased and stabilized lastly.The conductivity of the solution increased slightly,and the variation was within 20us/cm. |
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