Final Report of the Shipboard Testing of the Sodium Hydroxide (NaOH) Ballast Water Treatment System Onboard the MV Indiana Harbor

Abstract

In the summer of 2010, the National Parks of Lake Superior Foundation and researchers from the U.S. Geological Survey’s Leetown Science Center (USGS), received support from the USEPA’s Great Lakes Restoration Initiative (GLRI) to develop and trial a full-scale BWTS involving NaOH with applicability to U.S. flag vessels in Great Lakes trade. As part of this project, the research team enlisted GSI to undertake a status test on BWTS’ biological effectiveness and residual toxicity in the context of a single shipboard trial (one ballast uptake operation, one retention period, and one ballast discharge operation). The installation to be tested was a temporary and partial (two tank) prototype installed in two tanks on board the motor vessel (MV) Indiana Harbor, with alternate dosing approaches in each of the two tanks. The subject BWTS involved elevating pH by adding sodium hydroxide (NaOH, in the same formulation used for lye or caustic soda), retaining treated ballast water for a minimum period, and then neutralizing the ballast water prior to discharge. GSI’s status test involved collecting preliminary data on the biological treatment efficacy and residual toxicity (i.e., via whole effluent toxicity, WET, testing) from a single demonstration voyage based on measurement of ballast uptake into and discharge from two treatment tanks and two control tanks. GSI developed a detailed test plan that described the design of the single biological efficacy trial (including sample collection, analysis endpoints, sample handling and custody, WET, and data collection and recording), which was subject to review and comment by the NaOH BWTS development team prior to finalization (GSI, 2011). The GSI status test began on August 18, 2011, during normal vessel ballast intake operations in the port of Gary, Indiana, and concluded three days later on August 22 during normal vessel ballast discharge operations in the port of Superior, Wisconsin. On intake, GSI sampled harbor water that was loaded into four of the ship’s port side tanks (2P, 3P, 4P and 5P). There were adequate numbers of live zooplankton in the intake water (i.e., 43,000/m3 to 235,000/m3 of live organisms ≥ 50 μm) to warrant continuation of the trial. The water in two of these tanks (3P and 4P) was concurrently dosed with enough 50 % (w/v) NaOH solution to achieve a pH of about 12. Approximately 18 hours prior to the MV Indiana Harbor’s arrival in Superior an in-tank carbonation system was activated in both treatment tanks to neutralize the pH of the treated water to below 8.8, i.e., a level considered safe for release into the receiving harbor. Following the vessel’s arrival in port, the ballast water from the treatment tanks and the untreated water from the control tanks was discharged in sequence and sampled. As a single replicate, this GSI status test of the prototype BWTS is in no way conclusive or determinative. The results reported here provide only an indication of the system’s potential effectiveness relative to no treatment. In this single trial, BWTS-treated discharge contained live organisms ≥ 50 μm (i.e., zooplankton) in concentrations ranging 178/m3 to 441/m3. These concentrations are lower than control discharge densities which ranged from 100,000/m3 to 167,000/m3. Densities of live organisms ≥ 10 and < 50 μm in the treatment discharge ranged from 2 cell/mL to 8 cells/mL, while control discharge concentrations were higher, ranging from 53 cells/mL to 92 cells/mL. In terms of organisms < 10 μm, the trial produced inconclusive results with concentrations of both total coliforms and heterotrophic bacteria highest in discharge samples from one of the treatment tanks (4P). The results from a WET test indicate that the treated and neutralized discharge water produced no residual toxicity to green algae (Selenastrum capricornutum) or the fathead minnow (Pimephales promelas). However, in these tests, the treated ballast water significantly affected both survival and reproduction of the cladoceran Ceriodaphnia dubia, indicating possible residual toxicity. The BWTS developer asserts that this toxicity could derive from artifactual pHdrift during the WET test; pH increased by a maximum of about one unit over the 24 hour period following each daily renewal (Appendix 1). The GSI team did not control pH drift in daily exposures during the WET tests to avoid altering the inherent properties (including conductivity) of the discharge water subject to toxicity testing. Overall, the BWTS warrants further development and evaluation at the land- and ship-based levels.