The Ballast Water Management Convention’s discharge standards include limits on three indicator microbes that were adopted to protect public health. These limits were included at Brazil’s request after the devastating South American cholera epidemic—widely believed to have resulted from ballast water discharges—and repeated detections in ballast tanks of the bacterial strain that caused the epidemic.

In January 2015 we reported in Marine Pollution Bulletin that nearly all of the indicator microbe tests conducted during the previous 10 years under IMO’s G8 Guidelines were meaningless. The analysis is straightforward: in order to test whether a treatment system adequately reduces microbe concentrations, you must start with appropriate concentrations of those microbes in the untreated test water. At a minimum, the untreated test water must have higher concentrations than the limit that the treated water is supposed to meet. Examining all available data from type approval tests conducted since 2004, we found that the concentrations of indicator microbes in the untreated water were below the limit for treated water in 95% of the tests, and below detection limits (i.e. not a single indicator microbe was found in the samples) in nearly two-thirds of the tests.

These tests were all treated as valid tests, and the treatment systems were reported to have “passed” the tests and were granted type approval, because the G8 Guidelines don’t require any minimum concentrations of indicator microbes in the test water.

When asked about our results, officially IMO had no comment; unofficially, IMO made excuses for why it didn’t require meaningful tests. But why does IMO even require tests—and why are treatment systems certified as passing the tests—if the tests are meaningless? That wastes money, but worse, it misleads ship owners who believe that they are purchasing equipment whose efficacy has been demonstrated in tests, and misleads the public and policy makers into believing that the public’s health is protected by the BWMC.

IMO is now considering certain changes to the G8 Guidelines based on recommendations of the Correspondence Group. But although I sent copies of our paper to the IMO Secretariat and the Chair of the Correspondence Group 19 months ago, and requested that they find a way to fix this problem (we suggest various options in our paper), the issue is not even mentioned in the Correspondent Group’s report. This does a great and dangerous disservice to the public, especially in parts of the world where limited treatment of drinking water and domestic sewage leaves poor communities vulnerable to deadly outbreaks of water-borne disease.

Further Information:

Report: Tests of Ballast Water Treatment Systems are Flawed (New York Times online Jan 14, 2015)

Tests Used to Ensure Ships Don’t Carry Deadly Cargo Draw Sharp Criticism (Science online Jan 14, 2015)

Marine Pollution Bulletin article:  • published article    • preprint