Research On Microalgae Inactiation Of Ballast Water With Electro-catalytic/UV System

Ballast water is taken to ensure the safety of ship in voyage, but it caused the biological invasion which has become a worldwide environment problem. It’s primary to explore effective processing technology for ballast water cause of the IMO convention. The combination of electro-catalytic and UV has used to process ballast water in this study, which has efficient inactivation with low current output and short time. It provided a basis of how to inactivate microalgae in ballast water.To solve the problem of ballast water, an electro-catalytic/UV system had been established in this study. The optimal culture condition of microalgae had been researched, and a large-scale culture system had been established to provide adequate microalgae for ballast water, which was fast-growing and low-cost. Two kinds of electrodes were selected, and the performance of the single electro-catalytic system in microalgae inactivated were researched. The effect of electro-catalytic/UV system inactivating microalgae with better anode had been investigated, and it was proved that the electro-catalytic/UV system was feasible and efficient.The effect of electro-catalytic system inactivating microalgae had been determined under different hydraulic retention time and current density. The results proved that the mortality rate of microalgae increased with the increase of current density and hydraulic retention time. The mortality rate of Dunaliella salina after electro-catalytic treatment with Ti/SnO₂ anode had met the requirements of IMO under the conditions of HRT 3.0 s and current density 190 m A/cm2. And the sustained mortality rate of Dunaliella salina after two hours in the dark had met the requirements of IMO under the conditions of HRT 3.0 s and current density 160 m A/cm2. The survival amount of Platymonas helgolandica var. tsingtaoensis after electro-catalytic treatment with Ti/SnO₂ anode was100 cells/m L under the conditions of HRT 3.0 s and current density 200 m A/cm2.Electro-catalytic system with Ti/SnO₂-RuO₂ had better performance than electro-catalytic system with Ti/SnO₂ anode, which mortality rate of Platymonas helgolandica var. tsingtaoensis met the requirements of IMO under the conditions of HRT 3.0 s and current density 110 m A/cm2 as well as HRT 2.5 s and current density 180 m A/cm2. The sustained mortality rate of Platymonas helgolandica var. tsingtaoensis after 4 hours in the dark had met the requirements of IMO under the conditions of HRT2.0 s and current density 190 m A/cm2, HRT 2.5 s and current density 160 m A/cm2 or HRT 3.0 s and current density 80 m A/cm2. In these conditions Dunaliella salina couldbe inactivated completely.Ti/SnO₂-RuO₂ electrode had been chosen as the anode of electro-catalytic/UV system. And the effect of electro-catalytic/UV system inactivating microalgae had been determined, the microalgae was a mixture of Dunaliella salina, Platymonas helgolandica var. tsingtaoensis, Tetraselmis and Scrippsiella trochoidea. The results proved that the mortality rate of microalgae increased with the increase of current density and hydraulic retention time. The mortality rate of microalgae after electro-catalytic/UV treatment with Ti/SnO₂-RuO₂ anode had met the requirements of IMO under the conditions of HRT 3.0 s and current density 140 m A/cm2, HRT 2.0 s and current density 160 m A/cm2 or HRT 1.0 s and current density 180 m A/cm2. The sustained mortality rate of microalgae after 4 hours in the dark had met the requirements of IMO under the conditions of HRT 1.0 s and current density 130 m A/cm2, HRT 2.0 s and current density 130 m A/cm2 or HRT 3.0 s and current density 100 m A/cm2.Compared with single electro-catalytic system, electro-catalytic/UV system had better performance of inactivating microalgae in a short hydraulic retention time and low current. It is beneficial to extend the service life of electrode and cut the processing cost.