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Background
1.1.
Problem Definition
Invasions by non-native aquatic species are increasingly common worldwide, often causing
ecological and economic damage, and it is widely accepted that ballast water is one of the most
important vectors for transporting and introducing non-native species to new biogeographic
regions. Consequently, the International Maritime Organization (IMO), through the 2004
International Convention for the Control and Management of Ships’ Ballast Water and Sediment,
and more recently the proposed US Coast Guard (USCG) and Environmental Protection Agency
(US EPA) Vessel General Permit (VGP) have all put forward similar ballast water discharge
standards that limit concentrations of living organisms in different size or taxonomic categories
that can be released with ballast water. Current proposed ballast water discharge standards
include:
•
Less than 10 viable organisms per one m
3
greater than or equal to 50 µm in minimum
dimension
•
Less than 10 viable organisms per ml less than 50 µm in minimum dimension and greater
than or equal to 10 µm in minimum dimension
•
Less than the following concentrations of indicator microbes, as a human health standard: a)
Toxicogenic
Vibrio cholerae
(serotypes O1 and O139) with less than 1 colony forming unit
per 100 ml; b)
Escherichia coli
less than 250 cfu per 100 ml; and c) intestinal
Enterococci
less than 100 cfu per 100 ml.
To address the IMO and US discharge standards, technology developers and manufacturers
around the world have designed and built a variety of onboard ballast water treatment systems
(BWTSs) to achieve the prescribed discharge limits. A BWTS is a “Prefabricated, commercial-
ready, treatment systems designed to remove, kill or inactivate (prior to discharge) organisms in
ballast water. This includes all components, in an integrated fashion, required for shipboard
operation.” (ETV Protocols, 2010).
Prior to any approval or certification of a BWTS, all systems must go through extensive phased
development and testing from the laboratory to full-scale shipboard verification. This phased
approach not only addresses engineering challenges of scaling up, but also develops a
comprehensive understanding of the system’s mode of action (i.e., how the treatment kills or
removed organisms) and the dose-response of various organisms to a range of treatment
conditions. This knowledge and testing can be used to help identify indirect measures of system
efficacy and compliance. Three documents have been produce to provide guidance and
standardization of BWTS testing:
•
International Maritime Organization (2008) Resolution MEPC.174(58) Guidelines for
Approval of Ballast Water Management Systems (G8);
•
International Maritime Organization (2008) Resolution MEPC.125(57) Revised Procedure
for Approval of Ballast Water Management Systems that Make Use of Active Substances
(G9); and
•
ETV Generic Protocols for the Verification of Ballast Water Treatment Technologies, (2010)
EPA/600/R-10/146 (ETV).