It is now widely recognized that the discharge of ships ballast water is the main cause for the worldwide transfer of harmful marine organisms.In the present study,the rapid treatment of ships ballast water is achieved using hydroxyl radicals(·OH)generated from a strong ionization discharge combined with numbers of micro-streamer and micro-glow discharges.According to the guidelines of the International Maritime Organization(IMO),a series of ·OH killing experiments were then conducted using medium salinity ballast water.The results showed that,five species of algae from three different phyla and three kinds of bacteria were killed by ·OH consistent with the D-2 ballast water standard of IMO.Invasive marine species can be killed in low lethal dosage of 1.5 mg/L and within 6 seconds(only 1/300 of chlorine method),so that on-line treatment of ballast water is realized.Meanwhile,the possible relevant chemicals(RCs)assays showed that ships ballast water after treated by ·OH,did not produce chemical pollutants,and the quality of medium salinity ballast water with heavy pollution was also greatly improved.These results indicate that the ·OH treatment will become the effective method for the treatment of ships ballast water in the future.