The present thesis focuses on ballast treatment technologies and how these can be assessed by the buyer in order to select the most appropriate Ballast Water Treatment System (BWTS) for a Bulk Carrier Dry cargo ship. The first Chapter introduce the concept of biodiversity and the need for immediate actions to protect the environment from the invasion of alien or harmful organisms into ecosystems. Chapter two extends to the analysis of the subject with regard to the regulatory framework surrounding ballast management and its evolution. Chapter three focuses on the factors which a ballast treatment system can properly fit and operate in a ship and how ballast is being processed. Next, it is being analyzed the basic processing methods of all three categories in terms of the advantages and disadvantages of each method. In conclusion, the fourth chapter introduce the method of Multicriteria Analysis and the AHP - TOPSIS combinational model will be applied to the case study that follows. The data presented is real and based on a specific business profile of the shipping company from which they were taken from. It is therefore a comparison of four ballast treatment systems to find the system that is most suitable for the eight-year-old Supramax-Bulk Carrier (DWT: 56.735) ship of the company, after the process is completed. The paper is a good example of research in its early form as well in addition to the criteria mentioned, others are likely to emerge important factors that should in turn be weighed depending on the company that conducts it. Thus, its ease of application multi-criteria analysis performed above can be adopted by any shipowner, although it will need to consider more factors for the outcome of a more reliable result.