Ballast water treatment system testing: assessing novel treatments and validating compliance methods

Aquatic invasive species spreading via ballast water are a threat to marine biodiversity. Therefore, the International Maritime Organization (IMO) and the United States Coast Guard (USCG) adopted a Ballast Water Discharge Standard (BWDS) limiting discharge of organism through ballast water. To comply with the BWDS most ships need a Ballast Water Management System (BWMS). Filtration followed by chlorination or ultraviolet irradiation are the most common BWMS treatment techniques. In the case of chlorine or other active substances a neutralization procedure upon discharge is typically needed to remove residual toxicity. Every BWMS is thoroughly tested prior to receiving IMO and/or USCG type approval. Port State Control enforces the BWDS, creating a demand for indicative ballast water compliance tools.
The disinfection efficacy of didecylmethylammoniumchloride (DDAC) was investigated using algal monocultures and seawater. DDAC appears unsuitable as ballast water treatment substance because the required neutralization method using bentonite clay raises practical objections.
Bacterial counts using heterotrophic plate counting (HPC) is mandatory during USCG-type approval testing. However, this research demonstrated that HPC-results are not correlated with alternative methods like flow cytometry and/or qPCR. Therefore, it is recommended to reassess the mandatory use of HPC.
The FlowCAM automatically photographs water-entrained particles and conducts automated image-analysis to classify organisms. In UV-treated seawater, the FlowCAM was unable to automatically distinguish between living and dead organisms. Therefore, it is not considered a promising tool for indicative compliance testing.
After developing a concentration method, analysis of Adenosine TriPhosphate (ATP) was a promising compliance technique following tests in UV-treated seawater.