For more than a century, steel-hulled ships have relied on ballast water for maintaining transverse stability at sea. When a ship intakes ballast seawater, along with it comes bacteria, algae, microbes or small invertebrates. This potentially introduces non-native or invasive species into foreign biomes.

Figure 1. Shipping moves 80% of the world’s commodities, while also internationally transferring 3 to 10 billion tons of ballast water every year. Source: HachFigure 1. Shipping moves 80% of the world’s commodities, while also internationally transferring 3 to 10 billion tons of ballast water every year. Source: Hach

Two significant and widely recognized organizations have imposed regulations on ballast water discharge to prevent species exchange: the International Maritime Organization (IMO) and the United States Coast Guard (USCG). Their regulatory overlap, however, is causing confusion and uncertainty among those looking to meet ballast water management requirements in the most efficient way possible.

Conflicting regulations

The International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWM Convention), adopted by the IMO in February 2004 and fully implemented in September 2017, provides a framework for the treatment and discharge of ballast water. The IMO identifies two performance standards.

D1 standard

This establishes the appropriate volumes of ballast water exchanged. It requires ships to exchange a minimum of 95% of ballast water in the open sea. This requires pumping out the volume of each ballast water tank at least three times.

D2 standard

This standard covers approved ballast water treatment systems and specifies levels of viable organisms left in the water after treatment. It requires ships to conduct ballast water treatment to decrease the amount of discharged viable organisms below the limit.

In comparison, USCG legislation applies to discharge ballast water in U.S. waters, and identifies exchange or treatment operations and sediment management guidance. The USCG’s requirements are often stricter than those of the IMO. A ballast water management system that complies with the IMO may not satisfy USCG standards.

Both the IMO and USCG require installing a treatment system, mitigation measures, training requirements and a designated ballast water management officer. The USCG also requires clean, sediment-free ballast tanks and a report submitted to the U.S. authorities 24 hours before arriving at a U.S. port.

Testing methods

Establishing compliance relies on the ability to take ballast water samples and test them rapidly and accurately. The following are common testing methods.

Adenosine triphosphate (ATP)

ATP detection measures luminescence in the presence of luciferase enzyme from seawater extraction. Sampling ATP follows a three-step process:

· Extraction

· Determination

· Relative luminescence unit measurement

Several key advantages promote the use of ATP devices. It shows promising results after high-voltage electricity treatment. ATP devices are portable and relatively affordable for the industry, and results can be calibrated to correspond only to a certain organism size. Measuring total viable plankton biomass also enables the evaluation of all organism sizes. Finally, test results are obtained in less than an hour.

There are also some important disadvantages to this technique. Dissolved metals in samples can cause underestimates in detected biomass by inhibiting light distribution, or the presence of free ATP in the environment will result in overestimates. Extraction techniques can be time-consuming and complex for port state control officers. Additional filtration may be necessary to differentiate the sampled organism sizes, and when the ballast water is highly saline, additional dilution steps may be necessary. Also consider that relatively high concentrations of total suspended solids (TSS) may reduce filter efficiency.

Fluorescein diacetate (FDA)

Fluorescein diacetate (FDA) is a cell-specific identification method for cellular viability that estimates living planktonic biomass. Pulse-counting FDA, bulk FDA and Sytox FDA are the three FDA methods. Sampling involves staining, incubation and sample counting. FDA analysis enables the sampling of all organism sizes, depending on the method. The devices are also affordable for the maritime shipping industry.

Note that FDA does not necessarily stain all organisms and may be inconsistent with each sample. There is also a risk of filter damage or leakage. Staining methods may not discern between living and viable cells and staining dead or living cells may cause false positive results. The technique can also be time consuming — incubating stained samples takes 10 to 30 minutes and FDA analysis can take one hour or more.

Pulse amplitude-modulation (PAM)

PAM measures photosynthetic activity and phytoplankton biomass, which indicate viable cells. It analyzes living cells via variable fluorescence of chlorophyll in living algae. PAM fluorometry refers to the detection of photosynthetic performance parameters using fluorescing saturation pulses to stimulate species sensitive to light. The technique measures quantum yield of fluorescence, also known as instantaneous variable or maximum fluorescence.

PAM devices deliver results faster than ATP and FDA, and in some cases are also more accurate. Use requires minimal training, and devices are portable and easy to handle. Costs of PAM devices range between $4,000 and $15,000.

However, PAM accuracy decreases at water turbidity greater than 20 Nephelometric Turbidity Units (NTUs). Certain organism results are also prone to reading errors. Additionally, PAM fluorometry measures only concentrations of autotrophic organisms via chlorophyll.

The VIDA Act

On Nov. 14, 2018, the U.S. Senate passed the VIDA Act, which is legislation that provides for a uniform national standard to govern ballast water discharge by vessels. It establishes the Environmental Protection Agency (EPA) as the lead for establishing standards, and the Coast Guard as the lead for monitoring and enforcement.

The legislation brings clarity to instrumentation users. For example, previous doubt caused by the reluctance of the USCG to accept UV treatment as a satisfactory method to destroy all bio-forms present in ballast water is now clarified. The USCG must consider ballast water discharge standards that include nonviable organisms and most probable number (MPN) test methods to evaluate organism viability in USCG-type approval for ballast water treatment systems. This enables port authorities, flag states, vessel owners and shipping companies and all BWM manufacturers to determine system efficacy irrespective of ballast water treatment methodology.

The Hach BW680 handheld fluorometer

The VIDA Act establishes a clear path for Hach to deliver its BW680 handheld fluorometer as an optimal solution that targets port state controls, ship owners or operators and large system integrators, enabling them to rapidly assess if they are in gross noncompliance with current regulations. The yes-or-no test uses variable fluorescence to measure the presence of active chlorophyll in living systems (for example, phytoplankton). The device takes less than three minutes to complete analysis and is easy to use, but is also highly sensitive, registering traces of chlorophyll in the parts per billion range. The device is also upgradeable, which delays the need for new systems or devices as standards or capabilities evolve. Analysis data is stored for accurate record keeping.

Figure 2. The Hach BW680. Source: HachFigure 2. The Hach BW680. Source: HachThe BW680 is the most cost-effective and easy-to-use of all ballast water instruments. Studies by Gollasch et al. (2015) and Bradie (2016) reviewed several PAM devices. While PAM devices are relatively fast, portable and easy to operate, Bradie determined that the Hach BW680 delivered the most consistency; Gollasch et al. determined that it is the easiest handheld device to use of those that did not involve filtration steps. It is also the least expensive to purchase.

Given the conflicts in IMO and USCG regulations, meeting ballast water requirements in a cost- and time-effective manner using the BW680 provides shipowners exactly the information they need. By sampling on the spot, they know whether or not they comply before docking, in most cases eliminating the costly delays of bringing samples to a lab.

For more than 80 years, Hach has delivered innovative solutions for accurate water management. To access expert guidance and advanced technology to stay compliant in an evolving regulatory environment, visit Hach.

For more information about the implications of ballast water regulations on the industry and an opportunity to ask your questions around indicative measurement, join the Live Stream Event: Ballast Water Expert Panel hosted by Hach.

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