A ballast water solution for muddy waters
India has been advocating port-based, mobile ballast water treatment since 2013. Sandip Patil of Indian Register of Shipping’s Research and Innovation Center outlines the solution.
At recent sessions of the Marine Environment Protection Committee (MEPC) and the Pollution Prevention and Response (PPR) sub-committee, IMO discussed the issue of contingency measures for the Ballast Water Management Convention. What if a port authority finds a ship’s ballast water non-compliant with discharge standards after the use of treatment systems? In response to this, South Korea submitted a paper (MEPC 71/4/21) which is eye opening for industry.
The Korean delegation claims that systems are not working properly in ports with challenging water quality. Muddy water in some ports mean that either systems are clogging because of high turbidity, or ballasting operations are delayed beyond reasonable limits due to frequent start-stop back flushing. The paper suggested as a contingency measure that in muddy water ports systems should not be used and ballast water should instead be exchanged at high seas or mid ocean, where systems can be used effectively.
Canada (PPR 5/23/2) raised concerns that the convention could be breached if water is taken on untreated and debated whether this solution would be accepted by ports. Ship owners may have different concerns, regarding fuel consumption for exchange and treatment. Another question is whether it is necessary to treat water taken on from the high seas or mid-sea ocean water again
REAL WORLD PERFORMANCE
Through a detailed investigation with Global TestNet, the association of global ballast water management system testing facilities, we found systems are mostly tested at real world biological loads (species) but not at real world sediment loads. IMO’s G8 guidelines only specifies total suspended solids (TSS) conditions as >50 ppm, while the US Coast Guard (USCG) specifies >24 ppm. Neither gives an upper limit. In the real world, the TSS load can reach 1000 ppm, directly affecting ships’ cargo loading and unloading operations.
Global TestNet itself has noted challenges of testing in high sediment waters. In a statement the association noted that ‘testing extreme TSS values during land-based biological efficacy tests would not be possible because the extreme values would impair the biology of the organisms during the tests, rendering the tests invalid. Therefore the group agreed that filters should be tested against a high level of TSS outside the protocols for biological efficacy testing and agreed to generate a Filter Test Protocol for the evaluation of filter robustness to TSS levels that reflect real world scenarios.’
This means that IMO or USCG type approved systems may not work efficiently at higher sediment loads. Hence Canada has requested that the MEPC gather a list of ports with challenging water qualities (PCWQ).
According to filter experts, the 50-micron filters used in almost all type approved systems are not actually failing, but high suspended solids values mean that ballast operations are taking an enormous amount of time. To reduce that time, multiple filters are needed to offer a big catchment area, along with continuous back flushing to deliver the higher flows like (500-10,000m3/hr) required during non-stop ballasting operations. All this is not at possible in ships due to space constraint and huge capital costs.
Port-based mobile facilities delivering treated water can provide 10 times more catchment areas at sea chest suction to avoid frequent back flushing. These ballast water treatment boats – for example the BWTBoats concept developed by the Indian Register - can be provided with multiple series of modular filters for redundancy, thereby ensuring reliable ballast delivery to ships at all times. With space availability and viability through a shared business revenue model, BWTBoats can provide ballast at any TSS or sediment load.
Recent design developments in the BWTBoat concept have not only brought down its capital requirement by half but also mean that a ship doesn’t need to be modified or have a deck connection to receive treated ballast water. Ships can receive water at flow rates from 10-10,000m3/hr seamlessly without any delay or retrofitting costs. The system acts as an external ‘plug in’ to sea chests during ballast uptake.
The Korean and Canadian papers both referenced the possibility of receiving ballast from port-based facilities before opting for the exchange and treatment option. The Indian submission MEPC 71/4/25 gives details about the treated water delivering facility as a contingency measure (section 12.3) when systems installed on ships are not working at ballast uptake ports.
Before muddy water ports were identified as an issue, BWTBoats had a unique business model, acting as ballast water treatment (filtration and chlorination) facilities at all ports wherever user ships call. Now they can provide an additional benefit by offering only filtered water up to 50 microns to ships at muddy water ports. Ships fitted with their own systems can then treat the filtered water themselves to meet discharge standards.
An important distinction between shore reception facilities and mobile treatment facilities should be noted. The G5 guidelines of IMO’s convention have given us the concept of the shore reception facility, which involves transferring water to shore tanks for treatment, with water kept on hold for proper treatment and checking for compliance before safe discharge. Due to logistics and infrastructural problems as well as financial challenges, such facilities have yet to emerge anywhere.
If a mobile facility treats instantly and discharges immediately then is it valid from a technical and legal perspective? Legally there is no means for Port State Control to sample and test a reported case of non-compliance as water is being discharged immediately. So, holding time is not only important for proper disinfection but also to ensure PSC permission for discharge. This is possible in the case of shore reception, but not with instant treatment and discharge mobile facilities.
As an alternative, a BWTBoat with chlorine dosing equipment can dose non-compliant tanks through a recirculation technique and then allow for discharge once the number of organisms is within limits and PSC gives permission.
In addition to the BWM Convention, ship owners also need to comply with 0.5% sulphur cap regulations from 2020 onwards, which is expected to cost them approximately US$250 extra per tonne of fuel - either through using low-sulphur fuel, LNG or a scrubber installation. A ballast water treatment system retrofit if up to US$1.5 million on the ship is a further financial burden to ship owners during maritime slowdown.
Due to overcapacity and record low margins, we have seen surprising giant shipping companies making alliances. Normally shipping alliances run their ships on fixed routes and among fixed ports. If such alliances take one step forward to deploy BWTBoats at common ports it will not only save on the huge capital investments behind onboard systems but can also divert these funds to comply with 2020 sulphur cap.
At MEPC 70, the ballast water working group gave encouraging comments (MEPC 70/WP.10) for the implementation in practice of such facilities, especially for ships unloading cargo among fixed ports. The financial demands of regulations beyond ballast water and the current market situation may now make these facilities an even more attractive prospect.
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