The advanced EctoSys electrolysis as an integral part of a ballast water treatment system

Abstract

A full-scale 500 m3/h ballast water treatment system was tested according to the landbased type approval procedure of the International Maritime Organization (IMO). The system consists of disc filters followed by the advanced EctoSys electrolysis as an integral part for disinfection. The test water quality exceeded by far the minimum requirements for type approval testing. Due to the properties of the special electrodes used together with the striking disinfection effect, the disinfectants assumed to be produced inline by the EctoSys cell in river water were hydroxyl radicals, while in brackish water additionally chlorine and consequently the more stable bromine were formed. In river water, no residual oxidants could be detected in accordance with the assumed production of not responding, highly-reactive and short-living hydroxyl radicals. Accordingly, disinfection byproduct (DBP) formation was very low and close to the limit of quantification in river water. While in brackish water, initial residual oxidant concentrations were maximum 2 mg/L as chlorine and mostly brominated DBP (especially bromoform and bromate) were found. Overall considering this worst case test approach, the DBP concentrations of the treated effluents were below or in the range of the WHO Drinking Water Guideline values and therefore evaluated as acceptable for discharge to the environment. The stringent discharge standard by IMO concerning viable organisms was fully met in river and brackish water, proving the disinfection efficiency of the EctoSys electrolysis against smaller plankton and bacteria.