Method and a modular system for onboard treatment of ballast water

A method for treating and sterilizing ballast water onboard a ship during navigation, suitable for reducing and/or removing the contents of living micro-organisms, wherein the ballast water is filtered and then subjected to a sterilizing treatment by UV radiations within at least one storing tank, characterized by the steps of:

• providing at least an apparatus for recirculating and sterilizing the ballast water inside the storing tank, said apparatus comprising a UV radiation source device comprising a watertight casing,
• recirculating the ballast water from the storing tank, through the internal UV radiation source, and injecting and mixing the sterilized ballast water by a diffuser with the ballast water inside the storing tank;
• and
• continuing the recirculation and UV sterilization of the ballast water for a period of time suitable for substantially reducing or removing the contents of living micro-organisms into the ballast water, inside the storing tank,
• wherein the ballast water is continuously and repeatedly recirculated and made flowing through the UV radiation source,
• and wherein each of the sterilizing apparatuses is operatively connected to a control unit, and is characterized by the steps of:
• programming said control unit, with a sailing time (T1) and prefixed period of time (T2) for treating the ballast water, respectively;
• starting the recirculation and UV sterilization of the ballast water for the programmed treating period of time (T2);
• detecting if the treating period of time (T2) is elapsed and continuing the circulation and sterilization of the ballast water, when said treating period of time (T2) is not elapsed, respectively stopping the circulation of the ballast water and terminating the sterilization of the ballast water when the treating period of time (T2) is elapsed, holding the sterilizing apparatus in a stand-by condition;
• and
• detecting the required period of time (T3) for ending the navigation and starting again to recirculate and sterilize the ballast water, when the period of time (T3) required for ending the navigation is longer than a first reference period of time (TX) programmed in the control unit.