The Investigation Of Ballast Water Treatment System By Ion-exchange Membrane Electrolysis

The transport of marine species into foreign environments by ship’s ballast water has brought about large environmental and economic losses to the world’s coastal regions. Invasive species has been recognized as one of the four environmental threats to the ocean by The Global Environment Facility. In February 2004, the International Maritime Organization in London passed the International Convention For The Control And Management Of Ships’ Ballast Water And Sediments. This international Convention contains standards for ballast water treatment. It was against this background that the design of a ballast water treatment system by ion-exchange membrane electrolysis was studied. Initial exploratory research, based on theoretical calculation and experiments, were conducted. The four key components were:(1) Based on theoretical calculations, an experimental ballast water treatment system by electrolysis with ion-exchange membrane was designed to test its operations, with particular attention given to ease of operation and safety.(2) According to the requirements of the Convention and the recent frequency of red tide phenomenon, the species chosen to test the effectiveness of the ion-exchange membrane system were Dunaliella, Tetraselmis, Chlorella and Nitzschia closterium.(3) The efficiency of the ion-exchange membrane system was tested to determine the key factors that affected electrolytic efficiency and energy conservation while maintaining the integrity of the systems applicability of use onboard ships.(4) Experiments using electrolytic Chlorine (Cl2) or saturated chlorine water were conducted to test the effectiveness of killing the target organisms at varying chlorine concentration. These experiments revealed that chlorine concentrations required for neutralizing the organisms varied with 10 ppm required to kill Nitzschia closterium and Chlorella vulgaris,5ppm required to kill Tetraselmis and 4ppm to kill Dunaliella.