An excellent video training officially provided by Walport International and covering the key points of the management and particularly treatment of the ballast water. We are all aware of the IMO requirement of "ninety-five percent volumetric exchange" of the ballast water in the ocean - and there are three IMO approved ways in which requirement can be met.
First, by the "sequential" method - here, the ballast tank is first emptied, and then it is filled with replacement ballast water. The second method is called the "flow-through" method - here, they pump the water into the ballast tank and allow it to overflow; note that pumping through three times the tank's volume is considered to meet that ninety-five percent target of exchanged water. Third - the "dilution" method - in this one, a constant level of water in the ballast tank is maintained while water is both pumped in at the top and simultaneously discharged from the bottom. Again, three times a tank volume is usually considered sufficient to meet IMO standards.
The IMO BWM Convention addressing the issues of management and control of ballast water provides captains with another option - on board treatment of the ballast water. Filter out those bio-stowaways with some other IMO approved treatment system and you can forget about ballast water exchange. Maybe, but not yet... The system is still coming and it is getting closer, and what it means is that in some ten years the ballast exchange will be a thing of the past... A very good supplementary material for training of crew members and all people involved in the BWM, i.e. ballast water management.