For vessels with few ballast water discharges per year and for older vessels, fitting an onboard unit may well be uneconomical. In recognition of this, Damen has developed its unique InvaSave Mobile Ballast Water Discharge technology, enabling in-port ballast water processing and discharge.

As an onshore facility operated by professionals and specialists, it allows for better control of the treatment processes. Operation by experienced operators also ensures more accurate regulation of the desired levels of ballast water treatment.


  • More cost efficient for certain trades and ship types
  • No downtime installation and maintenance as with onboard BWT units
  • Increased reliability due to redundancy
  • Enables contingency measures in ports in case onboard BWT units fail
  • Self-sufficient - independent of external power supply and pumping capacity
  • Better compliance monitoring
  • Application of treatment technology unrestricted by space, pressure drop and power requirements.
  • Reliable solution for both ports and operators
  • Only requires fitting a deck connection at fraction of cost of full BWT retrofit
  • Suitable for sea, fresh and brackish water
  • Chemical-free technology
  • No blocked filters and no backflush in port of ballasting
  • Gravity ballasting for ballast intake still possible
  • Enables contingency measures in ports in case onboard BWT units fail


    Dimensions container 45’ x 8’ x 9,6’ (LxWxH) High cube
    Treatment capacity
    10 – 300 m³/h
    Power consumption 70-140 kW
    Effectiveness Designed for waters with low UV transmission, fresh, brackish and sea water
    Ballast Water processing Fully automated and monitored
    Generator US/EPA Tier 3/EU Stage 3A 160 kWe
    Design pressure 10 bar
    Noise level Meets highest standards



    What is ballast water?

    Ballast water is used to stabilise vessels and maintain their structural integrity. Typically ballast water is pumped in to special tanks while cargo is being unloaded, and discharged while cargo is being taken on board. Safety, weather conditions, the ship’s load, and the route taken are the primary factors that determine how much ballast water is taken on board a vessel for a particular voyage. More ballast is necessary for ships to sit lower in the water during stormy weather to avoid bottom impact from waves. Ballast water is also adjusted so as to balance the ship as it consumes fuel during a long voyage.

    What is ballast water treatment?

    Ballast water treatment is the process of treating ballast water in order to actively remove, kill and /or inactivate organisms prior to discharge. Ballast water treatment is different from the older process of ballast water exchange, which involved completely flushing the ballast water tanks during voyages in open water with sufficient water depth and distance from shore.

    Why is ballast water treatment needed?

    Ballast water taken on in one ecological zone and released into another can introduce invasive and nuisance aquatic species that may have detrimental impacts on the biodiversity, economy or human health of the receiving community and may in time become a serious threat to the environment.

    Bio-invasion is one of the four greatest threats to the world’s oceans today, alongside land-based sources of marine pollution, the over exploitation of living marine resources and the physical alteration and destruction of marine habitats.

    More than 90 per cent of global trade is carried by sea, and each year transfers of up to 12 billion tonnes of ballast water take place around the world. In order to reduce the incidence of bio-invasions, ballast water treatment reduces or renders inactive 99.9% of the living organisms in the ballast water.

    What is included in the type approval process?

    Technologies developed for ballast water treatment are subject to approval through specific processes and testing guidelines designed to ensure that such technologies meet the relevant standards. The approval consists of both land-based testing of a production model to prove that the discharge standards are met, and shipboard testing to prove that the system works in service.

    The most relevant guidelines are the IMO G8 Guidelines “GUIDELINES FOR APPROVAL OF BALLAST WATER MANAGEMENT SYSTEMS (G8)” and G9 “PROCEDURE FOR APPROVAL OF BALLAST WATER MANAGEMENT SYSTEMS THAT MAKE USE OF ACTIVE SUBSTANCES”. These technical guidelines are issued by the International Maritime Organization (IMO) and outline an evaluation procedure (including land- and ship-based testing) that equipment must undergo to demonstrate that it meets the ballast water discharge standards set out in the Ballast Water Management Convention.

    In addition, systems that apply for US Coast Guard Type Approval must be tested according to the “ETV Generic Protocol for the Verification of Ballast Water Treatment Technology”. The ETV protocol is similar to the G8 guidelines in that it contains evaluation procedures for system testing. However, it is much more prescriptive.

    How can the transport of small organisms evolve into such huge problems?

    There are thousands of marine species that can be carried in ships’ ballast water; basically anything that is small enough to pass through a ship’s ballast water intake ports and pumps.

    The problem is compounded by the fact that virtually all marine species have life cycles that include a planktonic stage or stages.

    Even species in which the adults are unlikely to be taken on in ballast water, for example because they are too large or live attached to the seabed, may be transferred in ballast water during their planktonic phase.

    The biodiversity, large numbers and prevalence of a planktonic phase for most species, are the primary factors that significantly increase the risk of bio-invasion via ballast water transfer.

    The difference between ballast water exchange and ballast water treatment

    This FAQ is aimed at the crew onboard a ship that has ballast water tanks and only addresses, in a birds view, the operational differences and the main technical differences. The biggest difference is that Ballast Water Exchange is done in mid ocean, where Ballast Water Treatment is done in port during the cargo handling operations.

    Ballast Water Exchange

    Ballast Water Exchange is a very demanding procedure which required a tedious preparation because each exchange method has its own pros and cons. All procedures require continuous attention to keep the vessel and her crew safe. Points of attention are keeping the propellers submerged, keeping the hull stress within limits, maintaining the visibility for safe navigation, maintaining the (intact) stability, preventing possible slamming of the bow, etc.

    Most of the crew sailing on ships with ballast water tanks already use a Ballast Water Exchange (BWE) method to comply with regulations. A quick recap learns us that Ballast Water Exchange is a method where coastal or port water is replaced by mid-ocean water during the voyage. Ballast Water Exchange methods in use are known as:

  • Sequential exchange, where the ballast water tanks are made empty and filled with mid ocean water;
  • Flow through exchange, where the mid ocean water, in three complete cycles, is pumped through in the tanks while the coastal ballast water leaves the tank simultaneously through the overflow;
  • Dilution method, where the mid ocean water, in three complete cycles, is pumped in through the top of the ballast water tank, and where the coastal ballast water leaves the tank simultaneously through the bottom connection of the tank.
  • The whole process and requirements are laid down in a Ballast Water Treatment Plan where the execution of the Ballast Water Exchange procedures are recorded in a Ballast Water Record Book which is to be kept up-to-date and available for review and survey by the port authorities or there representative.

    Ballast Water Treatment

    Ballast Water Treatment is often, when started up, a fully automatic procedure which have to be monitored for correct operation. When Ballast Water Treatment is applied, there is no more need to apply the Ballast Water Exchange procedures. Of course Ballast Water Exchange can be used, after approval for contingency operation. Many vessels are in the process of or have already been retrofitted with a ballast water treatment system. A typical retrofit installs a ballast water treatment in the existing ballast water system.

    Depending on the system in use, ballast water treatment is required at ballast water uptake and during ballast water discharge. Damen Green has partnered with three suppliers, two are specialized in continuous filtration and UV disinfection and one has specialized in continuous filtration with electro-chlorination. The electro-chlorination system is derived from the well-known Chloropac system for seawater cooling water treatment.

    When continuous filtration and UV disinfection, in an automatic and monitored process, is applied; during ballast water uptake, the ballast water is pumped by the own ballast pump through the continuous filter stage followed by UV-disinfection into the selected ballast water tank(s) as usual. During the uptake the filter is automatically cleaned (backwash) while the uptake procedure keeps ongoing. The backwash is pumped overboard by the backwash pump which is part of the ballast water treatment installation. During ballast water discharge, in an automatic and monitored process, the ballast water from the ballast water tanks are pumped with the own ballast water pump through the UV disinfection stage only, overboard as usual.

    When continuous filtration with electro-chlorination, in an automatic and monitored process, is applied; during ballast water uptake, the ballast water is pumped by the own ballast pump through the continuous filter stage (main stream) disinfection into the selected ballast tank(s) as usual. Directly after the ballast pump a water sample is taken to determine the amount of Sodium Hypochlorite which needs to be added to achieve the required level of disinfection. The Sodium Hypochlorite is injected in the main stream before the ballast water enters the selected ballast water tank(s). The Sodium Hypochlorite is, in a side stream, made onboard from seawater with the use of an electrolyzer and a degassing module to dilute and release the electrolyzer exhaust gases which are a residue of the Sodium Hypochlorite production. During ballast water discharge an analyzer connected to the ballast water piping before the overboard sea chest, determines the amount of Sodium Hypochlorite left in the ballast water to discharge. If necessary, residual chlorine is automatically neutralized with Sodium Sulphite before it is discharged overboard as usual, if no chlorine is measured, the ballast water is pumped, without further treatment, overboard as usual.

    Would it be permitted to treat ballast water only at discharge with a conventional ballast water treatment system, and, for example, to use it in a port as an IMO certified contingency solution?

    Unfortunately not, for a number of different reasons:

  • The type approval certificate of a ballast water treatment (BWT) system describes how it can be used. Normally, for a conventional BWT system, the IMO type approval certificate specifies whether the ballast water is treated before it enters or after it leaves the ballast tank. In case a BWT system is used to treat only at discharge it should be written in the IMO type approval certificate that this is also tested.
    The InvaSave is certified and tested specifically for use at the point of discharge. This will also be written in the IMO type approval certificate.
  • A conventional on board (UV based) BWT system uses a filter during ballast water uptake. Filtration is the critical first step in organism removal. It clears larger organisms while simultaneously removing sediments in the water. The automatic backwash cleans this filter and is discharged overboard. This is permitted since the backwash discharge contains the same organisms as the surface water. In the case that this filter is used (only) at discharge, the backwash will contains different organisms since it is taken in from a different area. Therefore, it cannot be discharged to the surface water.
    In the InvaSave container a secondary filtration train is installed, to clean the filter backwash from organisms. Therefore it is permitted to discharge the filter backwash to the surface water with the InvaSave in the case that the ballast water is not from the same area.
  • A conventional on board (UV based) BWT system is certified according to a standard IMO protocol. This protocol includes the requirement that the ballast water is stored for 5 days (land based tests) in the ballast tanks to allow time for the organisms to respond to the UV treatment. After 5 days the ballast water from the tanks is sampled and the number of organisms are counted. If the numbers are within the limits of the IMO Ballast Water management Convention, a BWT system receives its IMO approval. In the situation that a conventional on board (UV based) BWT system is used only at discharge there is no delay effect for to allow the organisms to die in the tank and the discharged ballast water will probably not meet the IMO standard.
    The InvaSave will be IMO certified without the need for storage time of ballast water in the ballast tanks for the die-off of the organisms.
  • What does the IMO Ballast Water Management Convention (BWMC) mean for my company’s operations?

    The BWMC was finally ratified on September 8th, 2016. This means, that as of September 8th, 2017, the convention will come into effect in full force for all participating nations (please see the IMO website for an up-to-date list of participants). All vessels >400 GT must from this day onwards carry an approved Ballast Water Management Plan and a Ballast Water Record Book. Furthermore, you are required to perform ballast water exchange to the IMO ‘D-1’ standard and keep track in writing of such operations up until the date of your next IOPP-certificate renewal. After this date, you are required to perform ballast water treatment, rather than exchange, using a certified ballast water management system. The corresponding IMO standard for ballast water treatment is called the ‘D-2’ standard.

    Why is there a market for the InvaSave technology?

    There are many scenarios for which an external treatment process makes sense. Take for example ship owners that cannot justify the costs of retrofitting vessels due to their age. Perhaps your vessel usually operates in areas where the Ballast Water Convention is not enforced (yet) but would now by chance like to visit a country where management is required. Or perhaps your vessels operate exclusively between a small number of ports; making available port-based ballast water management services could save you the costs of retrofitting. Sometimes, external treatment is the only option. Think of failure of your onboard ballast water management equipment, which at the moment unfortunately is a headache occurring often and of course always at the wrong moments. What happens to barges that don’t even have their own ballast water pumps? Or ballast water from drydocks? There are many, many possible reasons why your vessel is unable to comply with the required ballast water management scheme. No matter what the reason, however, the InvaSave offers the solution!

    Why is the InvaSave unique?

    The InvaSave is the world’s first, and only, mobile and stand-alone ballast water treatment system certified to the applicable IMO D-2 standard. There are no required holding times or pre-treatment steps, nor are any noxious chemicals used. Whatever ballast water goes in comes out certified compliant to the IMO D-2 standard in a single pass. This makes it unique; all our competitor’s products are certified merely for on-board treatment and require treatment at intake and discharge.

    Can the InvaSave be used for retrofitting?

    It is not intended for retrofitting. But, if it makes sense, then yes it can be used in that way. The InvaSave has been tested in rough, real-life scenarios on-board ships to certify its rigidity and survivability under actual working conditions.

    Does the InvaSave treat all salinities and water qualities?

    Yes, it does. The InvaSave has been tested and certified to work with fresh, salt and brackish waters and down to extremely low UV-transmission (UVT) values of 20%.

    What is the power consumption?

    Power consumption is in the range of 70 to 140 kW, depending on throughput. The InvaSave can be delivered with a built-in generator set (making it truly stand-alone) or alternatively be hooked up to a shore power connection.

    Can the InvaSave also be used to supply treated ballast water?

    Yes, it can. Water generated by the InvaSave is certified to the IMO D-2 standard. If this water is subsequently loaded as ballast onboard vessels, it is considered ‘treated’ as would be the case if a certified on-board system had treated the same water. Upon arriving at your destination, discharging the ballast via your onboard treatment system is considered fully complying with the Ballast Water Convention. This is a useful feature if, for example, your on-board treatment system breaks down when taking in water in port as ballast water. Simply take on board InvaSave-treated water instead of raw seawater and fix your onboard treatment system on the way to your next destination. This way, you can avoid having to wait in port for your ballast water system to be fixed!

    Is the installation of an on-board ballast water treatment system economically viable for my vessel(s)?

    For vessels with few ballast water discharges per year and for older vessels, fitting an onboard unit may not be economically efficient. Against this background Damen has developed its unique InvaSave Mobile Ballast Water Discharge Technology, enabling port-based ballast water management for routine service and emergency measures. This new technology broadens significantly the range of total ballast water solutions for ballast water compliance that Damen offers to its customers. Damen is always happy to think about the most commercially interesting solutions for our partners and clients. Contact us if you have any doubts!

    What about ballast water treatment on barges?

    Barges oftentimes do not have a pump room or even space to fit a Ballast Water Management System. As such, they especially will be in potential, immediate, trouble as of the 8th of September 2017, the date on which the Convention will come into effect. After all, performing an offshore ballast water exchange (to the required IMO D-1 standard) without ballast pumps is an impossibility. The InvaSave can help. I can travel with the barge on deck or remain on dry land and take care of ballast water treatment when necessary.

    How to comply to the BWMC at a dock or scrapyard or when carrying out salvage operations?

    When a vessel is in dock, it can’t always use its own Ballast water treatment installation to discharge ballast water directly into the dock. Ballast water has to be drained from the dock yard and treated or collected as waste. The same has to happen when a vessel is being scrapped or salvaged. Here the self-sufficient InvaSave with its capacity to treat ballast water at discharge only is the answer to be in full compliance with the BWMC.

    Can I discharge my ballast water when I have a failure in my ballast water treatment system?

    No, ballast water cannot legally be discharged when a vessel has a failure in its ballast water treatment system.
    These vessels can safely discharge their ballast water through the Damen InvaSave. Operators in Ports can have InvaSave systems available in order to provide emergency assistance and the required redundancy for ship owners to stay compliant with the BWMC at any time and without incurring costly delays.



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