Study On The DSA Electrocatalytic Treatment Of Algae In Ship's Ballast Water

The problem of biological invasion caused by the discharge of ship's ballast water in different places is the focus of the shipping industry and marine environment.The effective treatment of biological pollution of ballast water and the reduction of environmental pollution caused by ballast water are the most important issues for a large shipping country like China.This article analyzes the hazards of ship's ballast water and the development of pollution control technology,then decide to use electrocatalytic technology to inactivate algae in ship's ballast water.Using the new composite dimensionally stable anodes(DSA)material to construct the miniaturized electrocatalytic reaction device.It is hoped that the experimental results will provide technical guidance for the development and application of ship ballast water treatment technology by analyzing the effect and impact of new electrocatalytic technology on algae inactivationRuO2-SnO2-Sb2O5/Ti,IrO2-SnO2-Sb2O5/Ti and RuO2-IrO2-SnO2-Sb2O5/Ti DSA were prepared by thermal decomposition method in this experiment,and electrochemical performance analysis of the three DSA was performed.The results show that different coating materials affect the performance of the DSA.The addition of RuO2 can reduce the chlorine evolution potential of titanium-based coated electrodes,while the addition of IrO2 increases the oxygen evolution potential to a greater extent and prolongs the electrode life.Based on the analysis of the chlorine-oxygen potential difference,RuO2-IrO2-SnO2-Sb2O5/Ti coated electrode with large chlorine-oxygen potential difference and relatively lower chlorine evolution potential was selected as the optimal electrode for the electrocatalytic treatment of ballast water system.The study on five kinds of algae shows the feasibility of DSA electrocatalytic inactivation of algae in ship's ballast water.It proved that the inactivation effect of algae was different due to the size and different cell structure of algae.The DSA electrocatalytic inactivation study on five kinds of algae proves that the inactivation effect of algae is different due to different cell structures and sizes.Under the same experimental conditions,Chlorella v.ulgaris is the easiest to remove,followed by Platymonas subcordiformis,while the inactivation effect of Nitzschia closterum,Heterosigma akashiwo and Alexandrium tamarense are lower.Under the conditions of anode area of 7 cm2,hydraulic retention time of 60 s,and current density of 30 mA/cm2,the inactivation rate of Chlorella vulgaris can reach 98.91%,Platymonas subcordiformis is 88.94%,while the Nitzschia closterum,Heterosigma akashiwo and Alexandrium tamarense is only 37.54%,28.34%and 17.66%.Platymonas subcordiformis and Heterosigma akashiwo were selected for further experimental studies on conditional effects.The results showed that:the inactivation effect of algae in a certain range is positively correlated with hydraulic retention time and current density.The longer the hydraulic retention time and the greater the current density,the higher the algae inactivation efficiency.Under the same experimental conditions,the increase in anode area improves the algae inactivation effect by promotes the direct oxidation of the electric field.Electrocatalysis has a certain sustainability to the inactivation of algae,and the inactivation rate has been improved by standing algae to a certain extent time.By optimizing the conditions,electrocatalysis can achieve an efficient inactivation effect on algae.Under the conditions of anode area of 7 cm2,curreit density of 30 mA/cm2,hydraulic retention time of 40 s,and standing time of 30 min,the chlorophyll removal rate of Platymonas subcordiformis was up to 99.27%;anode area of 7 cm2,current density of 150 mA/cm2,hydraulic retention time 70 s,and standing time 30 min,the chlorophyll removal rate of Heterosigma akashiwo reached 99.09%.The analysis results of total residual oxides(TRO)in the effluent show that there is a certain concentration of TRO in the effluent immediately after electrocatalytic treatment,and the TRO concentration gradually decreases with the extension of the standing time.Correlation analysis between the decay of TRO concentration and the continuous increase of the inactivation of algae during the standing process shows that TRO in the effluent is an important reason for the continuous inactivation of algae after electrocatalysis.The mechanism of inactivation of algae by electrocatalysis was analyzed by measuring the content of malondialdehyde:(MDA),FDA fluorescence staining observation,and morphological observation of algal cells.The results showed that electrocatalysis caused lipid peroxidation of algal cell membrane,which changed the permeability of the membrane and caused damage to the cell structure.At the same time,the electrocatalysis caused damage to the organelles such as the chloroplast in the algae cell,which caused the cell metabolism disorder and death.