Science Serving Maryland's Coasts


Shipboard Evaluations of Venturi Oxygen Stripping During Continuous Routine Vessel Operations

Principal Investigator: 

Mario N. Tamburri

Start/End Year: 

2005 to 2011


Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science

Co-Principal investigator: 

Gregory M. Ruiz, Smithsonian Environmental Research Center; Peter D. McNulty, NEI Treatment System, LLC

Strategic focus area: 

Resilient ecosystem processes and responses


Objectives: The main objective of our proposed work is to extend the scope of VOS performance testing to include a different ocean basin (with different biota) and vessel type than is currently being evaluated and to conduct long-term monitoring of VOS efficacy for an entire vessel under routine, continuous operations as part of STEP program. This Phase IV: Commercial Ballast Water Treatment Technology Field Tests to evaluate VOS will be divided into two distinct parts or objectives: 1) Engineering Efficacy: Install and verify operational abilities, effectiveness to produce intended conditions, and reliability of the VOS systems onboard active vessels during long-term continuous operations. 2) Biological Efficacy: Test the ability of VOS to reduce concentration of living ballast water organisms, during normal vessel operations, to meet IMO standards. Methodology: The first objective will be addressed by evaluating engineering efficacy. NEI will work with the ship owner to install and test the mechanical components of the treatment technologies to determine operational abilities, safety, and reliability using standard engineering principles. This will include the periodic, routine monitoring of physical conditions of treated and untreated ballast water (e.g., temperature, salinity, dissolved oxygen, pH), impacts on the vessel structurally and operationally, and basic system performance over a minimum of two years. The second objective will be addressed by evaluating biological efficacy. Periodically over the two year project, replicate samples will be collected and evaluated from multiple ballast tanks at two or three depths immediately after filling and just prior to discharge after a voyage. The number of living organisms per unit volume will be determined from the samples for two different size classes: greater than 50 um and between 50 and 10 um, using direct microscopic observations, selective staining, and flow cytometry. Regrowth experiments will also be used to help identify "viable" phytoplankton. Finally, the three specific indicator microbes (E. coli, V. cholera and intestinal Enterococci) will be quantified using direct plate counts, chromogenic substrate methods, and if required, monoclonal antibody tagged with fluorescein isothiocyanate (FITC) immunoassay for toxic V. cholera. In addition to changes found before and after voyages, all values will be compared to IMO standards and those of the USCG once they are released. Rationale: Based on recommendations by the Ballast Water Technology Demonstration Program manager and previous proposal reviewers, we have taken a phased approach in evaluating a potential ballast water treatment to prevent aquatic invasions and ship corrosion. Our work began four years ago with a proof-of-concept study as Phase I (Tamburri et al. 2002). In February 2003, we began our NOAA, Fish and Wildlife Service and MARAD supported project as Phase II to evaluate deoxygenation through Venturi Oxygen Stripping (VOS) as a ballast water treatment to prevent both the transport of aquatic invasive species in ballast water and to reduce ballast tank corrosion. This second phase combined laboratory, dockside mesocosm, and dockside pilot-scale experiments. Results from these tests demonstrate that VOS can effectively kill most of the organisms found in ballast water, meet International Maritime Organization (IMO) ballast water standards, provide a direct benefit on the shipping industry through dramatic reductions in ballast tank corrosion rates, and importantly, is scalable to any ballasting flow rate (Tamburri et al. 2003). In September/October 2004, we installed a VOS system onboard the TECO bulk carrier Pat Cantrell for Phase III, full-scale controlled experiments as the vessel operates from Jacksonville, FL to Port Author, TX. Initial mechanical testing has demonstrated that the VOS system operates effectively and reliably onboard a vessel. The large majority of this NOAA-funded Phase III work will be completed prior to initiating Phase IV (described below), which we are proposing to begin in June 2005. Although the hypoxic conditions produced by VOS are toxic to the majority of aquatic organisms, it is the combination of reduced oxygen levels (between 0.2 and 1.0 mg/1), lowered pH (between 5.5 and 6.0), and mechanical disruption as organism pass through the venturi injector that is responsible for its efficacy. For example, results at the pilot-scale show that phytoplankton are no longer viable after 4 to 5 days of exposure to VOS treated water because of reduced pH (Hinga 2002; Tamburri unpubl. data). Furthermore, although pathogens such as Enterococci, Escherichia coli and Vibrio choels are facultative anaerobes and adapted to acidic conditions found in digestive systems, they are extremely susceptible to rapid drops in pH with 100% mortality after only 30 minutes of exposure to a 2 unit pH decrease (Merrell and Camilli, 1999; Tamburri unpubl. data). NEI Treatment Systems is the developer of the patented VOS ballast water treatment. They have been working very closely with various vessel owners on design studies for shipboard applications. Based on performance verifications as part of previous academic studies (funded by the Ballast Water Technology Demonstration Program), the VOS system has now advanced to the developmental stage where a prototype has been installed onboard a vessel. Although we are currently conducting controlled experiments on a vessel operating in the Atlantic and Gulf of Mexico, the final definitive Phase IV step of continuous treatment of all ballast water of several years of routine vessel operations is critical to convince regulators and the shipping industry that this treatment system is safe, effective, and reliable. Through a collaborative demonstration project we hope to take advantage of US Coast Guard's Shipboard Technology Evaluations Program (STEP) and funding from NOAA and several other sources to directly involve the shipping industry by providing vessel regulations exemptions (through STEP) and sharing much of the costs for treatment system installation and evaluation. This proposed Commercial Unit Field Test will also involve a different vessel type than the Phase III trials that operates in the Pacific (capturing different physical and biological conditions) to assure the broad applicability of VOS. Several shippers are very interested in VOS for their vessels as both an invasive species and corrosion prevention system. Thus far in 2004, NEI Treatment Systems has submitted proposals for VOS systems to eight US and foreign shipping lines. We will therefore work with one of these companies to select the most appropriate vessel and route to be evaluated. In particular, discussions have already begun with Matson Navigation (US Flagged Carrier) about the use of a bulk carrier operating in the Pacific through the ports in Hawaii, California and Oregon, as a test platform. We will work closely with the vessel owner to evaluate mechanical efficacy and reliability, and will verify the ability of the VOS system to consistently discharge ballast water that meets IMO standards.