Study On Bacteria Inactivation In Ballast Water By Combination Of Micro-pore Filtration And UV Radiation

With the development of international trade and economic globalization, an increasing number of ships more frequently cruise among seaports in the world. To be safe and stable, ballast water need to be exchanged before ships' sailing. However, a phenomenon of biological invasion via ballast water is growing seriously, which is making harmful effects on marine ecosystem, human health and seaport city's economic development. Therefore, more attention has been paid to this kind of pollution in all seaports' countries. Thus, it is significant to find an effective method for controlling and preventing from the harmful aquatic organisms and pathogens spreading via ship's ballast water. According to the properties of ballast water, our laboratory has proposed a method for ballast water treatment, i.e., the combination of micro-pore filtration and UV radiation (MPF & UV). And this thesis focused on the marine bacteria inactivation systematically.Based on the provisions of D-2, three kinds of simulated ballast water were prepared by mixing natural seawater with Chlorella, Nitzschia closterium and Platymonas subcordiformis respectively. In the MPF & UV treatment system, two factors including flow rates (1-9m~3/h) and initial algae concentration were regulated, and the inactivation rate of bacteria was tested. The experimental results show that the inactivation rates are low while the simulated ballast water mixed with Chlorella or Nitzschia closterium is treated by UV radiation, the influence of the flow rates and the initial concentration of algae on the inactivation rates is obvious, and the inactivation rate is reduced with the flow rates and the initial concentration of algae increasing. The data of bacteria inactivation treated by MPF were invalid in most cases, the flow rates and the initial concentration of algae have little influence on the inactivation rates, and the sequence of the inactivation rates is as follows: Platymonas subcordiformis > Nitzschia closterium > Chlorella. In the MPF&UV system, with the flow rate of 1-9m~3/h and the initial input of algae of 10~4-10~5ea/mL, the inactivation rates of bacteria in the three kinds of water are 83.11%-100% with Chlorella, 92%-100% with Nitzschia closterium, and 100% with Platymonas subcordiformis respectively; and the average rates are 98.08%, 99.04%, and 100% respectively. The detailed analyses confirm that neither MPF nor UV radiation can be satisfied with the requirements of removing plankton and bacteria in ship's ballast water, only combining MPF with UV radiation can the requirements be.Ballast water treatment using the combination of Micro-pore filtration and UV radiation has advantages of no damage to water properties, no secondary pollution, broad-spectrum and highly-efficient. Therefore, this technology has a bright prospect.