Ballast water (BW) to maintain a ship’s stability carries multitude of aquatic invasive species and poses serious threat to the ecosystems at destination ports. To minimize transfer of harmful aquatic organisms and pathogens at the global level, Ballast Water Treatment Systems (BWTS) were introduced along with the recommendation of IMO standards (Regulation D-2), where indicators are in ratios. However, observations across samples from the same ballast tank are not additive like average speed of cars. The paper describes an index of overall quality of treated BW by multiplicative aggregation of the indicators of viable organisms and specific microbes. The index value  indicates compliance of D-2 standard across all the indicators. The index satisfies desirable properties, including statistical test of the equality of means of two sample GMs (SGMs). Identification of critical indicators and confidence interval around mean SGM, giving a range of index values indicating compliance, are novelties of the paper. The proposed index can be decomposed into the Index of Viable Organisms and the Index of Specific Microbes, facilitating the computation of relative importance. A separate index of physical and chemical factors can be computed by multiplicative aggregation. Empirical linear relationships can be fitted with each proposed index as dependent variable and ratio of value of variables in a year ( and base year ( as independent variables. Empirical verifications are planned to highlight salient features of the proposed indices along with the efficiency of different filtration units associated with BWTS.