Study On The Effect And Mechanism Of The Inhibition And Removal Of Algae By Electrochemical Oxidation Using Boron-doped Diamond Electrode

Water pollution lead to the eutrophication of slow-flow water bodies,which lead to blooming phenomenon caused by the algae outbreak occurred in eutrophic water.In order to control the amount of algae,the study took Microcystis aeruginosa as research object,and was conducted by Boron-doped Diamond(BDD)anode and stainless steel cathode.The effect of inhibition and directly removal of algae by electrochemical oxidation of BDD anode because of it's good electrochemical properties were investigated.The mechanism of inactivation of algae cell and the degradation of algae toxins by electrochemical oxidation were investigated.The influence of controllable factors including current density,electrolysis time,A/V,inter-electrode gap,initial pH and uncontrollable factors including initial density of algae,the growth status of algae and ion concentration(-Cl,2-4SO,2-3CO and-3NO)on the inhibition of algae by electrochemical oxidation using BDD anode were investigated.The results showed that the inhibition of algae increased with the increase of current density,A/V and electrolysis time,while decreased with the increase of the initial density of algae.However the effect of inter-electrode gap was not obvious.Completed inhibition of algae by electrochemical oxidation using BDD anode could be obtained under the initial pH in neutral and acidic conditions.The inhibition of algae in stable growth phase was better than the inhibition of algae in log growth phase.The inhibition of algae increase with the concentration of-Cl and 2-4SO in the solution.However the inhibition of algae decrease with the concentration of 2-3CO in the solution.The inhibitory effect of-3NO concentration was not obvious.The active chlorine was the main substance on the inhibition of algae on the late culture.In the study of algae removal by electrochemical oxidation using BDD anode,the current density,A/V,inter-electrode gap and the initial pH were optimized according to the removal efficiency of algae and energy consumption.The optimum parameters were as follows: a current density of 17 mA/ cm2,the ratio of A/V of 9.75 m-1,inter-electrode gap of 0.7 cm and the initial pH of 7.0.The initial density and growth status of algae had significant effect on algae removal efficiency.The reaction is first-order kinetics(k=0.0324,R2=0.997),and energy consumption was 37.69 kWh/ m3 within 90 min by electrochemical oxidation under the condition of optimum parameters and the density of algae in the log growth phase was 1.2×109~1.4×109 cells/ L.Energy consumption and time show a good linear relationship.At different current densities,the pH,conductivity and UV254 of the solution decreased or increased firstly and then stabilized.While the dissolved oxygen(DO)of the solution increased firstly,then stabilized,decreased lastly at different current densities.The structure,integrity,photosynthesis system,growth rate of algae cell could be destroyed by electrochemical oxidation using BDD anode.The photosynthesis and respiration could also be disturbed.The microcystins could be degraded effectively while the microcystis aeruginosa destroyed.The degradation efficiency of total microcystin-LR was 91.17% within 90 min under a certain condition.The concentration of extracellular MC-LR increased firstly and then decreased.The concentration of intracellular MC-LR and total MC-LR decreased with electrolysis time.The electrochemical oxidation could not only degraded MC-LR,but also degraded other substances in solution,which generate the substances with smaller molecular weight.