Research On Microalgae Inactiation Of Ballast Water With Axidant And UV System

The off-site discharge of ballast water may lead to the spread and invasion of marine species,even destroyed the original ecological balance.The International Maritime Organization has developed Ballast Water Management Conventions to regulate discharge standards for ballast water.Therefore,it is of practical significance to seek efficient and low consumption ballast water treatment technology.This project uses oxidant and ultraviolet radiation composite technology to treat microalgae with diameters ranging from 10 to50 ?m in ballast water.This experiment is researching on microalgae inactivation with H 2O2,HClO and UV separate systems,as well as H₂O₂/UV,HClO/UV,H₂O₂/HClO,H₂O₂/HClO/UV composite systems under different influent oxidant concentrations,HRT and UV radiation intensity.At the same time,the continuous algae removal performance of composite system has carried on.The attenuation of the total residual oxide of the composite system under different conditions was also analyzed.It has some guiding significance for the establishment of ballast water treatment system and the optimization of its operating parameters.The microalgae inactivation experiment results of H₂O₂ single system and HClO single system showed that the microalgae inactivation effect increased with the increased of HRT and influent concentration.The algae inactivation effect on Dunaliella salina was the best,followed by Platymonas helgolandica tsingtaoensis,and Tetraselmis,and the worst is Scrippsiella trochoidea.The inactivation effect of the UV system on microalgae increased with the increased of radiation intensity and hydraulic residence time?HRT?.The inactivation effect of H₂O₂/UV composite system and HClO/UV composite system on microalgae increased with the increase of the concentration of influent oxidant,HRT and radiation intensity.HRT=2.5 s,H₂O₂ influent concentration is 70 mg·L^-1,and when the radiation intensity is 11.5 m W·cm^-2,the inactivation of Platymonas helgolandica tsingtaoensis,Tetraselmis,and Dunaliella salina can reach the IMO Convention emission standards.When HRT=2.5 s,hypochlorous asid concentration was 105.6 mg·L^-1,and ultraviolet radiation intensity is 11.5 m W·cm^-2,the inactivation effect on Tetraselmis and Dunaliella salina can reach IMO Convention emission standards.In the H₂O₂/UV composite system,the decomposition of H₂O₂ is mainly affected by the influent concentration,and the radiation intensity,HRT and catalyst have less influence.The inactivation effect of mixed algae is better than that of the se parate system in the H₂O₂/HClO composite system.The attenuation of the Total Residual Oxide?TRO?of the composite system decreases with the increase of HRT and radiation intensity,with the influent and increases as the concentration increases.The attenuation of TRO with in 120 hours is similar to that of the remaining viable algae in the continuous algae control effect of the composite system and then tended to be flat.TRO tends to be in a stable state after 120 hours,but the concentration is about 40 mg·L^-1,which unable meet the emission requirements of IMO and must be treated and then discharged.The algae inactivation rate of H₂O₂/HClO composite system was^-2.855 at HRT=2.5 s,H₂O₂ concentration 70 mg·L^-1 and hypochlorite concentration 105.6 mg·L^-1,which compared with the concentration of H₂O₂ and HClO single system used alone,the concentration of H₂O₂ and HClO decreased by 20 mg·L^-1,35.2 mg·L^-1,respectively.The effect of compound H₂O₂/HClO composite system on inactivating mixed algae can meet the discharge standard with in HRT was 2.5 s,H₂O₂ concentration was 70 mg·L^-1,and hypochlorite concentration was 105.6 mg·L^-1,and ultraviolet radiation intensity was 11.5 m W·cm^-2.In the study of continuous microalgae inactivation effect,when HRT=2.5 s,the H₂O₂/HClO composite system need influent concentration of H₂O₂ and hypochlorous acid of 60 mg·L^-1 and 70.4 mg·L^-1,however the H₂O₂/HClO/UV composite system only need influent concentration of H₂O₂ and hypochlorous acid of 40 mg·L^-1 and 52.8 mg·L^-1,and radiation intensity of 5.75 m W·cm^-2,after 120 hours,microalgae inactivation could meet IMO Convention emission standards.