Ballast water treatment requirements – how to manage the challenges and uncertainties

Vessel ballast water serves to increase the vessel’s draft, change the trim, regulate the stability and maintain stress loads within acceptable limits during voyages and loading and unloading operations.

When discharged in ports of call, however, it may also release animals, plants, bacteria and pathogens from the vessel’s previous areas of operation. If these organisms establish reproducing populations outside their native or historical range, they may become “invasive” and be considered an aquatic nuisance species.

The IMO International Convention for the Control and Management of Ships’ Ballast Water and Sediments (referred to as the Ballast Water Management (BWM) Convention) addresses the potentially damaging effects of international shipping’s use of ballast water. The BWM Convention will enter into force 12 months after ratification by 30 states representing 35% of world merchant shipping tonnage. As per May 2014, 38 countries have ratified the convention but there are still 4.6 percentage points lacking on the tonnage requirement. The dates for formal implementation are therefore still uncertain.

With the IMO BWM Convention lagging, the US government has introduced its own Ballast Water Management Program administered by the US Coast Guard (USCG) and US Environmental Protection Agency (EPA). The US regulations are already in force and this means that the US implementation schedule governs vessels operating in US waters. No ballast water treatment systems (BWTS) are per today approved by the USCG and an Alternative Management System (AMS) has been introduced as an interim measure to allow treatment systems approved by other bodies to be installed while awaiting USCG approval.

Challenges
With the introduction of the ballast water treatment requirements, international shipping is facing one of its most comprehensive challenges. The treatment systems are business critical for the vessel’s operation. This, coupled with limited experience of their performance and a multitude of different technologies, all with their limitations and strong points, makes the ballast water treatment strategy one of the most important choices for years to come.

Owners/operators will need to place significant trust in the supplier’s data and information. The careful selection of a treatment system can mitigate specific feasibility requirements, such as space constraints, electrical load limitations and the integration of control systems, optimise operational performance and save costs. A treatment system that is optimal for one ship is unlikely to be the best solution for another ship.

Diversity of water
The diversity of water that the BWTS will have to deal with is important when selecting the right system for a given operational profile. To obtain type approval, tests have to be performed on standard quality water. However, these water qualities may differ substantially from the water the system is likely to experience throughout its operation. The turbidity, opacity, temperature and salinity of the intake water are some of the challenges facing the
treatment system. Holding time requirements related to some systems may also be incompatible with the vessel’s scheduled loading cycle. Some ballast water treatment systems may not be as efficient in brackish or fresh water, while other systems may need increased maintenance when operating in river water and certain filters may have a higher incidence of clogging in icy or muddy waters.

Cost and support
In a newbuilding project, the major selection factor is the equipment’s cost. Apart from that, one of the most important considerations when selecting a system is the Operational Expenditure (OPEX), such as running and maintenance costs. For a new ship, a high Capital Expenditure (CAPEX) could be acceptable if the OPEX is low, but, for an older vessel, a low CAPEX is likely to be more favourable even though the OPEX could be high. Some systems require maintenance to be performed by a specialist from the maker, while other systems can be maintained by a trained crew. The maintenance requirements and support from the vendor worldwide should also be considered when selecting a BWTS.

US approval
The USCG Type Approval process is more stringent and rigorous than the IMO process. As a result, existing IMO Type Approved systems may not necessarily meet the USCG requirements and will require re-testing and possibly re-design. The USCG Type Approval process is still under development. To facilitate compliance, the USCG has created an Alternative Management System (AMS) process whereby foreign Type Approved systems may be used on a vessel for up to five years after the vessel is required to comply with US ballast water discharge standards.

How can DNV GL assist?
Taking advantage of our unique position as the leading classification society for approval of ballast water treatment systems, DNV GL has developed a systematic analysis procedure to find the optimal system for any given vessel/operation.

At the beginning of a feasibility assessment project with a customer, DNV GL will propose a set of selection criteria. DNV GL will then, together with the customer, agree on the weighting of the different criteria to be used in the analysis. The six main groups of assessment criteria are evaluated in detail for the selected treatment technologies. Each criterion is then broken down into sub-criteria, which are finally evaluated separately. The
selection criteria are not necessarily equally important to different customers. DNV GL will therefore, together with the customer, agree on a weighting for each selection criterion. A risk-based approach will be used, in which the weight of each criterion is decided given the likelihood and consequences of a certain event happening or failing to happen.

The combined score and weighting add up to a table where the different overall systems’ performance may be compared. All in all, the solution lies in leveraging the necessary competence and available information and consequently reducing the ultimate risk when selecting a treatment solution for the vessel. This is exactly the kind of services DNV GL offers in its BWM evaluation process.
Source: DNV GL (Dry Bulk Update)