A decade of ballast water data submitted to the U.S. EPA: A trend toward improved compliance

To manage the environmental impacts from ballast water and other discharges from ships sailing in waters of the United States, the U.S. Environmental Protection Agency (EPA) put in place the Vessel General Permit (VGP) in 2008. For ships that will install and use a ballast water treatment system (BWTS) to comply with the VGP's requirements for ballast water management, annual reports must be submitted that include the results of sampling and analysis of two types of parameters: bacteria and biocides. From all BWTS, the concentrations of three bacteria must be reported. If a BWTS uses biocides as part of the treatment process, the concentration of relevant biocides and derivatives must also be measured and reported. To date, the United States is the only country to require routine sampling and analysis from ships discharging ballast water into federal waters. We analyzed data submitted to the EPA for a decade (from 2014 to 2023), representing nearly 18,000 reports. First, data were "cleaned", e.g., to remove duplicate reports. Surprisingly, nearly one quarter (23 %) of the reports did not include the required bacteria data. Evaluating the data showed that non-compliance with the parameters' limits was relatively low, <3 % for either of the bacteria (Escherichia coli and enterococci; total heterotrophic bacteria results are only reported, as no limit is stipulated for them). Non-compliance for biocides was <10 %. Evaluating non-compliance of both bacteria and biocides showed more consistency: <2 % of reports were non-compliant for both parameters. Encouragingly, compliance has improved over time, with the best (lowest) non-compliance rates in recent years (2020-2023).