Great Ships Initiative: Land-Based Performance Evaluation in Ambient and Augmented Duluth-Superior Harbor Water of Eight Commercially Available Ballast Water Treatment System Filter Units

This Great Ships Initiative (GSI) technical report describes outcomes from controlled freshwater operational and biological evaluations of the performance of eight commercially available filter systems (FSs). Tests took place at the GSI Land-Based Facility located in the Duluth-Superior Harbor (DSH) of Lake Superior (Superior, Wisconsin, USA) during September and October of 2013. Test objectives were: (1) to provide reliable information on FS operational and biological performance in freshwater under controlled conditions, and to support limited performance comparisons across FSs; (2) to explore any trade-offs between operational and biological performance endpoints; and (3) to support FS, and thus ballast water management system (BWMS), freshwater performance improvements. The eight commercially available FS units represented a range of filtering technologies and nominal pore sizes. Overall, FS biological performance expressed as percent reduction of total organisms in the ? 50 ?m size class (i.e., zooplankton) ranged from 31.2 to 99.9 percent, with performance relative to larger zooplankton (i.e., macrozooplankton) in the ? 50 ?m size class consistently high across nominal pore sizes. FS removal of organisms in the ? 10 ?m and < 50 ?m size class (i.e., protists) ranged from 22 to 89 percent. There was a statistically significant and large magnitude negative relationship between FS nominal pore size and percent reduction for microzooplankton in the ? 50 ?m size class, as well as for organisms in the ? 10 ?m and < 50 ?m size class (i.e., protists). That is, the smaller the nominal pore size the greater the percent reduction of organisms. These estimates of FS effectiveness relative to the smaller organisms in the ? 50 ?m size class are conservative, in that live/dead status was not taken into account. Operationally, all eight FSs performed without significant mechanical failure and without requiring manual servicing for the duration of testing. Measured operational performance parameters did not strongly correlate (positively or negatively) with biological performance such that clear and necessary “trade-offs” could be asserted. In particular, based on GSI findings, volume lost to backflush is not necessarily greater with higher organism removal, though unmeasured operational parameters, such as energy consumption may be. Overall, findings from this study help inform choices to increase BWMS efficiency and effectiveness for end users and the environment.

2014_GSI_Land Based Evaluation of Eight Filter Units