Studies On Compined Process Of High Gradient Magnetic Separation And UV For Ballast Water Treatment Technology

With the development of industrial and shipping, the biological invasion through the shipballast water loading and replacement has brought more and more serious threat to the healthyand sustainable development of marine environment and marine ecosystem. This dissertationaims at studying a novel combined process of high gradient magnetic separation（HGMS）–ultraviolet for microorganism removal from ballast water. The influencing factors ofultraviolet irradiation technology, effect of HGMS used as the pretrement process for UV andeffect of combined process for microorganism removal from ballast water had beeninvestigated.The ultraviolet static and dynamic water treatment device was designed andmanufactured. The orthogonal experiment showed that the dose of UV is the most significantfactors of ultraviolet water ballast inactivation efficiency. The turbidity and microorganismconcentration had also an important influence on the inactivation effect. The variationregularity of ballast water microorganism removal rate, the microorganism removal rateimproved with the UV dose and turbidity increasing, was verified.The dynamic experimental of UV irradiation technique results showed that the UVmethod has high inactivation efficiency, when the unit water ballast receives more than orequal to124346J/cm~2UV dose, and turbidity is less than or equal to5NTU. It also pointedout that the UV inactivation efficiency was largely influenced by UV energy propagation inthe case of the sufficient UV dose.The influence factors of HGMS for ballast water treatment was studied. The orthogonalexperiment showed that the magnetic field intensity was the most important factor, and thenthe other following factors were residence time, magnetic dosage, stirring intensity, initialturbidity. The turbidity removal rate by HGMS increased with magnetic field intensity andmagnetic dosage increasing, and decreased with the increasing of flow rate. The effect ofHGMS is related to magnetic medium characteristics. With the filled amount increasing,turbidity removing rate was increased and different diameter of the magnetic medium steelwool has different effect to the water turbidity. Mixed magnetic medium has better treatmenteffects than the single diameter of the magnetic medium. HGMS also could removemicroorganism. To make sure that the treated turbidity can reach5NTU, the working conditions of high gradient magnetic separation of ballast water treatment should becontrolled within the intensity of not less than12.7mT, the flow rate no greater than10L/h,magnetic dosage of about400mg/L; magnetic medium filling rate of high magneticseparation device of3~4%, and with the magnetic medium composed of different diameterstainless steel wool as far as possible.The treatment efficiency of the composite technology was conducted and the resoultshowed that the composite technology showed better processing performance in the treatmentof high turbidity water ballast. In comparison to separate UV inactivation technology,composite technology decreased0.7~0.9orders of magnitude in residual microbialconcentration.The effect of high gradient magnetic separation-UV composite technology for theballast wate treatment was studied through the continuous flow experiment. Experimentalresults showed that, the microbial inactivation rate of composite process reached99%, theresidual concentration of Escherichia coli, Staphylococcus aureus, Chlorella, total bacterialafter treatment were respectively16.5cfu/100mL,39.9cfu/100mL,54.9cfu/100mL and73.4cfu/100mL, which meet microorganism concentration standards consistent withConvention on the Control and Management of Ships’ Ballast Water and Sediments, and theturbidity of effluent was1.5~2.4NTU.