Electrolytic treatment of ship's ballast water

The raw seawater and the seawater with one kind of algae (Nitzschia closterum, Dicrateria spp., or Pyramidomonnas sp. with a density of 10 5 cells/ml) were simulated as ships' ballast water. They were treated by electrolysis with an initial Free Active Chlorine (FAC) concentration of 5mg/l and all target organisms were killed. Laboratory corrosion tests were also carried out to assess the corrosive impact on ballast tank metal caused by the treatment. The results showed that the chlorinated ballast water could accelerate metal corrosion compared with un-chlorinated ballast water. The AC power consumption of ballast electrolyzing is US$3.5/1000m 3 by theoretical calculation. Also, tests showed that the treatment could reduce not only phosphate, but also Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) as well as increase the Dissolved Oxygen (DO) in the seawater.