Optimizing ballast water management: An evaluation of ballast water treatment system performance in challenging water conditions

The movement of ballast water is a major pathway for introducing aquatic
invasive species. Ballast water management systems (BWMS) aim to reduce
species introductions, but their performance varies under challenging
water quality conditions. This study assessed BWMS performance in a
freshwater port with impaired water quality by comparing harbour
conditions to challenge water criteria for type approval testing defined
by the International Maritime Organization and U.S. Environmental
Protection Agency, and by analyzing paired harbour uptake and ballast
discharge samples. Of 18 harbour samples, 67% approached or exceeded
challenge water criteria for ≥50 μm organism abundance, while 22% and 11%
exceeded criteria for dissolved organic carbon and total suspended solids.
All nine discharge samples met limits for small organisms (≥10 to
<50 μm), but eight exceeded limits for larger organisms (≥50 μm)
despite >99% reduction from uptake levels. Abundance of larger
organisms in discharge was affected by uptake water quality (ultraviolet
transmittance and organism abundance), and BWMS treatment type/filter
size. The findings suggest that raising challenge test criteria may
improve BWMS reliability across environmental conditions.