Join AOGdigital on Facebook Join AOGdigital on LinkedIn Join AOGDigital on Twitter


Preparing for ballast water ratification

By  Justin Salisbury, Cathelco managing director Wednesday, 03 February 2016 08:17
Rate this item
(1 Vote)

It is estimated that more than 50,000 vessels will need to be fitted with ballast water treatment systems over the next decade. Cathelco’s Justin Salisbury explains.

BWT System. Images from Cathelco.

The ratification of the International Maritime Organization’s (IMO) ballast water management convention has been a long time coming, but most people agree that we are now in the final phases of the countdown.

The clock began ticking in late November 2015 when Indonesia became the 46th state to sign bringing the gross tonnage figure tantalizingly close to the 35%, which will trigger implementation.

It is estimated that more than 50,000 vessels will need to be fitted with ballast water treatment (BWT) systems over the next decade. When the convention comes into force it will apply to all vessels greater than 400 gross ton operating internationally, including submersibles, floating platforms, floating storage units (FSUs) and floating production storage and offloading vessels (FPSOs).

Although there are exemptions within the IMO regulations for smaller craft, such as tugs and offshore supply vessels operating from a port to a nearby offshore oil field, the nature of the oil industry means that these vessels may be redeployed to other areas of the world.

If the vessels enter US territorial waters, they are immediately subject to the US Coast Guard regulations, which were published in 2014 and are now being enforced. Furthermore, the US Environmental Protection Agency’s (EPA) ballast water management requirements of the Vessel General Permit (VGP) 2013 have to be observed. These apply to all seagoing vessels, which have ballast tanks.

If the convention is ratified this year, then vessels will have to be installed with a BWT system at their first in International Oil Pollution Prevention (IOPP - MARPOL I) survey following entry into force.  Therefore, for most ship owners and operators there is a window of up to five years in which a BWT system must be fitted that will create enormous pressure on dry-docking space worldwide.

It is not yet clear whether extensions will be offered by the IMO, but as far as the US Coast Guard is concerned, any applications for extensions must be received by the end of December 2015. Not surprisingly, forward thinking operators are already entering into a dialogue with manufacturers in an attempt to beat the rush.

Choosing a BWT system

Worldwide there are well over 50 manufacturers of BWT systems using various technologies to treat ballast water. The choice of technology will, of course, depend on the size and ballasting rate of the vessel combined with its operational characteristics.

For instance, systems using heat treatment, de-oxygenation and inert gas production tend to have fairly large footprints and are generally fitted on vessels with very high flow rates such as very large crude carriers (VLCCs).

In the case of vessels such as container ships, bulkers, ferries and various types of offshore supply and support craft; it is worth examining in line systems where the water is treated immediately after being taken on board.

These include filtration/UV irradiation, electrochlorination and ozone treatment, which generally take up less space. However, it is worth noting that electrochlorination systems do not work in fresh water without additional equipment.

It is also worth considering the merits of a chemical free system, referred to as a G8 system by the IMO. Clearly, it is desirable to have a G8 system because it means that no production, storage or handling of chemicals is required. Also, systems involving chemicals will have an additional neutralization process that tends to make them larger and more complicated.

Will the system work in all water conditions – fresh, brackish and salt? You may also like to enquire how it performs in challenging water conditions with high levels of turbidity. For instance, there are wide variations in the performance of UV systems offered by different manufacturers.

Newbuild and retrofit installations

Final assembly of BWT system

In newbuild applications, space will have been allowed for the BWT system, which can often be supplied skid mounted to simplify installation. Nevertheless on smaller newbuilds there can be constraints on the size of the footprint.

In some instances there can be a strict limitation on the footprint of the system, but not on the height, enabling some equipment to be repositioned above.

In the case of retro-fit installations, the first priority will be a survey to identify usable space for the equipment and pipework pathways. This will cover pipework break in, equipment installation and discharge points. Here, 3D scanning can assist in the survey process, but it is rarely a substitute for a thorough manual survey.

Thought needs to go into the planning of access routes for equipment. In some cases, the easiest option may be to cut a hole in the hull as a direct way of getting the main unit into position.

Will the system be completely integrated with the ballast room controls? If so, your BWT supplier should begin a dialogue with your vessel’s software supplier. This should be done at the earliest possible stage to iron out any problems.

BWT systems can affect the flow dynamics of the existing pipework. Make sure your supplier has a thorough understanding of these implications and knows how to design the pipework accordingly. As the system needs to be scaled to the maximum capacity of the pumps, if more than one pump is used consecutively, this will have a significant impact.

Filtration and UV systems

As previously mentioned, various types of BWT systems are available to ship owners and the choice of system for a particular type of vessel will depend on its size and method of operation.

Of the 70 systems on the market, roughly a third are based on filtration and UV irradiation, so it is worth looking more closely at the way in which they operate and some of the reasons why they have emerged as a leading technology.

One of the reasons is that these systems are relatively compact in comparison with other treatment systems, space being a major consideration in virtually all applications. Furthermore, the technology is well proven having been used for municipal water applications for decades, plus the fact that the UV method is chemical free.

Having said this, there is no silver bullet with BWT systems and the filtration/UV combination is best suited to vessels with flow rates of 3000 cu m and below where no throttling back of flow is operationally acceptable. However, this still encompasses more than 40,000 ships including supply vessels, pipe layers and numerous types of oil and gas tankers up to 60,000-tonne dwt together with a variety of container ships and other commercial vessels.

Taking the Cathelco system as an example, during uptake the sea water passes through the filtration unit where the larger organisms and sediments are removed. At regular intervals the retained material is back flushed and discharged at the original ballasting site with a very minimal reduction of the ballast water flow during the back flushing process.

The seawater continues to UV treatment where smaller organisms, bacteria and pathogens are rendered harmless before the water passes to the ballast tanks in compliance with IMO regulations. It is essential that the BWT system can automatically adjust to different qualities of seawater, compensating where necessary for changes in the level of sediment.

Some systems merely measure the amount of sediment contained with the seawater and raise the intensity of the UV lamps accordingly. However, the Cathelco system goes a step further by using a UVT sensor, which measures the UV light transmittance through a sample of seawater before it reaches the UV chamber.

From this data, the automation control unit calculates the correct UV dosage. This precise level of control also helps to reduce the power consumption of the lamps. Maximum power is only used occasionally when the conditions demand.

Justin Salisbury, managing director of Cathelco Ltd., joined the family business in 1982 as export sales manager. In 1992, he took the decision to diversify the business into ICCP hull corrosion protection systems, and was instrumental in setting up a subsidiary in South Korea to serve the shipbuilding market. This was soon followed by subsidiaries in Singapore, the Middle East and India, as well as the establishment of a dedicated BWT research and development center in Kiel, Germany.

Read 7277 times