Treatment system of ballast water in oceanic ships using hydroxyl radical (?OH) based on strong electric-field discharge

Exchanging ballast water from ships might cause the interactive bio-invasion of different seawater, and break ecological balance. Therefore, we described a ship ballast water system which generates hydroxyl radical from strong electric field ionization discharge. The discharge at atmospheric pressure could ionize O2 in air and gaseous H2O to form a large amount of oxygen active particles, which were injected into a tube of the ballast water treatment system to generate a high concentration of ?OH solution through the cavitation effect. The ?OH solution could kill harmful micro-organisms in ballast water quickly and efficiently. Test results showed that, after being treated by the system at a flow speed of 10 t/h, the single-cell algae and bacteria in ballast water were almost completely eliminated, and the micro-organisms did not reactivate at 48 h and 120 h. In the treated ballast water, the concentration of malondialdehyde(MDA) obviously increased while BOD and COD decreased significantly. According to the MDA test, ?OH probably kills algae and bacteria though preoxidating their cytolipin. The treatment can effectively lower the pollution from the ballast water.The results indicate that solution of high ?OH concentration significantly improves the quality of ballast water, hence it relieves the environmental threats of the ballast water discharge on local marine system.