Simulation And Verification Test On Quantitative Values Of Staphylococcus Aureus In Watercraft Ballast Water Processed By UV

With the continuous development of marine transport,the ballast water consumption increases gradually with shorter retention time,which exacerbates the invasive species and pollution brought.To protect marine environment and ensure our sustainable development,the ballast water treatment is imperative.Among many kinds of treatment methods,ultraviolet treatment has been focused for its advantages of strong sterilization without chemical addition and secondary pollution,safe and reliable operation,and low cost etc.It is widely applied in ballast water treatment.Aimed for the effective treatment of ballast water,an ultraviolet reactor was designed,which mainly includes the cylinder,UV lamp,glass casing,orifice plate and electrical components.Reactor’s slenderness ratio was 15:1.The orifice plate was added in the middle section of reactor to effectively improved the hydraulic characteristics.By the modification,the radial mixing can be achieved when the ballast water goes through the reactor,and the turbulence of ballast water flowing in the reactor was enhanced.To investigate the hydraulic characteristics of reactor,the methylene blue-tracer experiments of no-orifice plate reactor and orifice plate sets reactor were conducted separately,and the results were compared.The author different combinations of inlet and outlet were set to study the effect of their positions on the hydraulic characteristics of reactor.Results show that the reactor has some blind sectors,and the effective reactor volume is smaller than the actual volume.When the flow rate is 0.5m~3/h,the orifice plate has no influence on the hydraulic characteristics of reactor;but when the flow rate increases to 1m~3/hin the middle of the orifice reactor,the hydraulic condition is improved,and the faster the flow rate,the greater the improvement.Through the static quasi parallel light experiment,the effect of the microbe initial concentration,the strength of ultraviolet light on the ultraviolet treatment was discussed.The result shows that under this experimental condition(the significant level is 0.05),when the ultraviolet irradiation is the same,the yellow staphylococcus initial concentration,the intensity of ultraviolet irradiation,the logarithmic inactivated rate of staphylococcus is not influenced.But the effect of ballast water turbidity is significantly.The two phases of experiments under different turbidity obtained by static tests verified the simulation results.The CFD simulation was used for modeling and analysis of the designed reactor.By comparing the CFD simulation with the tracer test,the results show that CFD simulation results are close with that of tracer test,which means that CFD simulation can reflect the actual engineering situation to some extent.To use CFD to optimize the reactor structure,improve the treatment effect is feasible.The CFD simulation of water mark can also show that orifice plate can enhance ballast water flow in the reactor of turbulence,making radial mixing more fully.By using DPM model to simulate the microbial particle tracking,the results also show that the reactor has come blind sectors and short flow and so on.Moreover,the microbes in the reactor running track always represent obvious radial fluctuation,orifice plate can make the ballast water in the reactor radial mixing more even and the orifice plate can improve the hydraulic characteristics of reactor under certain condition.Combined DPM model with light distribution model,the UV irradiation dose which received by microbe were obtained under the ballast water turbidity of 2.5 and 45,and the rate of flow were 0.2,0.5,0.8,1,1.2,1.5,2m~3/h.According to the simulation results,this research set up a receiving UV irradiation dose-flowrate model for ballast water through the reactor.And dynamic test was conducted with artificial ballast water,and its results were compared to the receiving UV irradiation dose-flowrate model.The analysis indicates that the simulation results coincided with dynamic basically with the experimental results under the condition of this experiment,the error is less than 13%.Therefore,the combined modeling of CFD and ultraviolet light distribution is reliable to predict the effect of the reactor on ballast water in actual situation.The research results can provide technical basis for UV treatment of ballast water.The model in this paper can effectively simulate the treatment effect of ultraviolet radiation on ballast water,which may be the foundation of ship sewerage treatment process optimization and other aspects.