The Disinfection System Of Coal-based Carbon Membrane Coupled With An Electric Field For The Treatment Of Simulated Ballast Water

Since the late 19th century,various problems of ecology,economy and food health have arisen due to the increase of ballast water discharge.International Maritime Organization(IMO)has specified that ballast water must be treated to meet with the relevant requirements before it can be discharged.Therefore,in order to solve the problem of alien invasion according to the Ballast Water Management,an disinfection system of coal-based carbon membrane coupled with an electric field was constructed,and treatment of Vibrio cholerae and Escherichia coli with high efficiency in simulated ballast water was realized.In this study,the disinfection system of coal-based carbon membrane coupled with an electric field was applied and the disinfection performance of Vibrio cholerae and Escherichia coli in simulated ballast water and variations of flux of carbon membrane were studied in the conditions of electric voltage,bacteria kinds and density,rotate speed of peristaltic pump,conductivity,electrode distance.The morphological changes of carbon membrane and bacteria before and after applying voltage were observed by scanning electron microscope and then the effect of voltage on disinfection performance was analyzed.From results we can know that:The permeate flux of the carbon membrane and disinfection efficiency decreased with the addition of bacteria density.When the bacteria density in the simulated ballast water was less than 5.00 × 104 CFU/mL,the disinfection efficiency was 100%;Disinfection efficiency reached 100%at rotate speed of peristaltic pump of 7.5 rpm,because high rotate speed can promote the permeation of bacteria,while it inevitably made some of bacteria penetrate through the carbon membrane quickly without being killed;High conductivity was beneficial to generate more total residual chlorine(TRC)during the electrolysis of seawater,and thus disinfection efficiency and permeate flux were improved;The permeate flux of carbon membrane showed a decreasing trend with the reduction of the electrode distance,because short distance can produce strong electric field and enhance the electrochemical reactions which built a big obstacle for permeate flux.The concentration of halogenated hydrocarbon generated in ballast water disinfected with different voltages was detected by gas chromatography-mass spectrometry,including CHCl3、CHCl2Br、CHClBr2 and CHBr3,and the model of Yangshan Deepwater Port in Shanghai was built by software MAMPEC v3.0 developed by Amsterdam Vrije University to carry out the environmental risk assessment of the disinfected ballast water.The results showed that the risk quotient value RQ of CHClBr2 was 0.99 at 3.0 V electric voltage,which was at the edge of the risk limit.The remaining measured risk quotient values were all very low.Therefore,if the electric voltage is less than 3.0 V,the concentration of halogenated hydrocarbon released by disinfection system will not pose a threat to the marine environment.