This work deals with multicriteria choice of ballast seawater treatment method for shipboard installations in bulk carriers of 60,000-90,000 DWT (i.e., of the Panamax-Kamsarmax vessel category). The alternatives examined are (alphabetically quoted): Cavitation- Deoxygenation, A1; Cavitation-Ozonation, A2; Filtration-Electrolytic Chlorination, A3; Filtration-UV Irradiation, A4; Flocculation-Magnetic Separation, A5; Sedimentation by means of Hydrocyclone-Electrolytic Chlorination, A6. The criteria used are (quoted in order of descending weight): lifecycle economic cost,/1; lifecycle environmental cost,f2; reliability, f3; simplicity,f4; maturity of technology, f5; perspectives for further development, f6. Fuzzy numbers were used for the assignment (by experts) of (i) weights to the elements of the input criteria vector and (ii) grades to the input preference matrix, in order to count for uncertainty. The output ranking vector was A4>Ai>A2>A3>Ae>A5, where the sigh '>' means 'better than' at both (low and high) resolution levels, indicating a robust solution. Sensitivity analysis was performed for all criteria used and the results are discussed. Relevant optimization techniques were also developed to generalize the methodology presented herein.