Examples from LNG carriers sector show how fitment of ballast water management systems can be avoided and also provide experience of the requirements of larger vessels
Examples from the LNG carrier sector show how fitment of ballast water management systems can be avoided and also provide experience of the requirements of larger vessels
The first question to ask when selecting a ballast water treatment system is: Does the vessel require a ballast water treatment system? If the operator is in the fortunate position of being able to design a vessel from scratch for a particular trade or operating parameters, there may be ways around the requirement.
This was the case with Kairos, an LNG bunker supply vessel owned by Babcock Schulte Energy (BSE), a joint venture between Babcock International Group and Bernhard Schulte Shipmanagement. Kairos was developed using Babcock’s Fuel Gas Supply Vessel Zero technology, which eliminates the release of boil-off and flash gas to the atmosphere during normal operations. Nauticor, a provider of LNG for maritime customers, is chartering Kairos to serve marine clients in the North Sea and Baltic Sea, the Klaipëda LNG fuelling station in Lithuania and the Linde LNG terminal in Nynäshamn.
The designers have taken the bold step of not incorporating a BWTS by moving the accommodation forward to overcome LNG bunker vessel design constraints relating to line-of-sight from the wheelhouse. That also had the benefit of longitudinally balancing the ship, reducing the need to transfer ballast. Coupled with the low-density LNG cargo, this design removed the need for seawater ballast and associated treatment systems. Only a limited volume of permanent fresh-water ballast is used for trim purposes.
As the number of vessels using LNG as a marine fuel increases, this design could become the template for a new generation of bunker vessels. LNG PRO Bunkers chief executive Alexander Prokopakis told Ballast Water Treatment Technology that the company is examining its options, with 20 designs on the table, of which three are ballast-free.
Some vessels require relatively little ballast water, and Turkey has proposed to MEPC 74 that rescue tugs and other specialised vessels be considered for special treatment. The Turkish paper notes that rescue tugs do not draw in harbour or seawater or expel ballast water on a regular basis. The main use of ballast water is to trim the rescue tug for towing operations. A survey of 1,000 operations within the Turkish tug boat fleet revealed only 20 trimming events.
There is very limited space within a rescue tug to fit even the most modular of ballast water treatment systems, and the impact on fulfilling the BWM Convention would be to remove a large proportion of the Turkish tug fleet from operation. One proposal is to trim the tug by transferring drinking water from tank to tank. This drinking water is usually transferred from the land, and not generated from seawater. Under the Turkish proposal a guidance document would supplement the BWM Convention for those specialist vessels that rarely discharge ballast water.
For larger vessels, the selection process is guided by cost and the trading of the vessel. For instance, the owners and operators of large LNG carriers (LNGC) have certain advantages over other shipping sectors when it comes to the fitment of ballast water treatment systems.
As in the case of the rescue tugs, smaller vessels have limited room among their machinery spaces and so may need to use a modular ballast water treatment system. This is not necessarily a negative, but it does demand more planning. And while ballast water treatment systems have various power requirements, some LNGCs have a source of relatively cheap energy from the boil-off gas.
Another important consideration for LNGCs is the training and safety culture required for the crew. It is a step change for a bulk carrier crew to go from the culture required to operate a large but relatively benign vessel to the more complex analysis required with some ballast water treatment systems. On a sophisticated ship like a chemical carrier or LNGC, the training and operation demands required of a crew are already of a higher level, and the operation of a ballast water treatment system may be less daunting.
LNG carriers also tend to be younger and are less likely to have undergone refits and alterations in their short lives. The vessel will be closer to the original spec, but even series-built sister ships will have significant differences in the machinery spaces (see Case Study), which is where the planning of ballast water treatment systems requires careful thought.
Marine engineering firm 21 Knots has undertaken the planning, engineering and retrofit of several types of ballast water treatment systems, and founder and chief executive Nitesh Ranvah notes that the same issues occur.
Mr Ranvah notes that owners tend to spend months visiting trade shows, talking to manufacturers and negotiating price. In his opinion, deciding the make and model should be a low priority compared with scanning the available space and sourcing the engineering. Otherwise millions of dollars of income could be lost through time wasted fitting a compromised system.
USCG approval is key
A key concern for any choice of ballast water treatment system on a large LNGC is the potential to trade into US waters. Few operators predicted the rate at which US LNG exports would grow. At an output of 8.9Bn ft3 by the end of 2019, up from a predicted 4.9Bn ft3 in 2018 (according to the US Energy Information Administration), the export capacity of the US will soon be the third-largest in the world, behind only Australia and Qatar. As a consequence, four additional export terminals have received all necessary approvals from the Federal Regulatory Commission and the Department of Energy, amounting to a combined additional LNG export capacity of 7.6Bn ft3. Under current and future US LNG export scenarios, being able to de-ballast in US waters is a requirement, which means choosing a US Coast Guard type-approved system.
Similarly, the de-ballasting must be able to take place in a manner that does not interfere with the cargo-loading procedure. American company Ecochlor was one of the first to receive USCG type-approval for its filtration and treatment with the ClO2 BWTS.
Ecochlor’s newly appointed vice president of business development Andrew Marshall outlines the specific demands of the LNGCs when it came to ballast water treatment.
“The challenges facing LNGCs are similar to those of any vessel with a high ballast-pumping rate. Specifically, finding a ballast water management system that has the ability to reliably meet those high rates over an extended ballasting period,” he says.
“In some LNG vessel designs there are constraints on available space for the integration of piping and treatment units, but with proper planning and selection of the right BWMS, these issues can be overcome.”
The design of a newbuilding would naturally take into consideration the space required for modern compliance equipment, from ballast water management systems to exhaust gas scrubbers, but space can be at a premium when retrofitting a ballast water treatment system.
Mr Marshall notes that a modular system could have a smaller footprint. “A compact, modular system with minimal footprint provides several options for placement on the vessel,” he says.
The Ecochlor system starts with precursor tanks that have a footprint of 12.7 m2 and treatment systems with a footprint from 0.3 m2 upward.
The pumping rate is another factor when assessing a ballast water treatment system for a large LNGC: “The maximum flow-rate capacity of an Ecochlor ballast water management system is up to 16,200 m3 per hour, with an option for up to three ClO2 injection points,” says Mr Marshall. For a 150,000 m3 LNGC, Mr Marshall says only one ballast water management system is needed for the entire vessel.
Elsewhere, Erma First of Greece secured a fleet-wide agreement from Norway’s Golar LNG in December 2017 to supply its USCG type-approved BWTS Fit system. Erma First uses filtration, electrolysis and electro-chlorination as its treatment method. The company said in a statement that its equipment would be installed “on up to 16 LNG vessels”, which potentially covers the whole Golar fleet.
Alfa Laval’s USCG type-approved UV-based ballast water management system was specified by Nakilat, the Qatari shipping and maritime company with the world’s largest LNG fleet. Two of Alfa Laval’s PureBallast 3.1 systems of 2,000 m3/h will be retrofitted. PureBallast 3.1 was selected, stated Alfa Laval head of PureBallast Anders Lindmark, for its small footprint, simple installation and ease of use.
Large vessels with high cargo-loading rates, and therefore large volumes of ballast water being taken on board, have another option: not to treat the ballast water as it enters the tanks. This is the approach offered by Coldharbour Marine and Environcleanse, among others. Environcleanse’s inTank model is an electrolysis and chemical injection ballast water management system.
The Environcleanse treatment methodology is relatively simple: all port-based ballasting and de-ballasting activities are completed as normal. There is no filtration, no increase in power demand and no concern for ballast water quality.
During the voyage, an electro-chlorination cell uses clean seawater to create sodium hypochlorite. At the same time, ballast water is circulated and the newly created disinfectant is injected into the circulation loop. The mixture is then returned to the ballast tank through the in-tank mixing nozzles, which diffuse the biocide in the tank. The levels of biocide are monitored and confirm the lack of new growth during the voyage.
It is not a requirement for ballast water management system to have USCG type-approval for global operation, but it has become a de facto standard by which many systems are judged. Ballast Water Treatment Technology maintains a database that contains 112 ballast water management systems. Of these, at the time of writing, 17 have been type-approved by the USCG and a further 12 are under review pending type-approval. In some cases, a ballast water management system has already been approved in its original form, but variations, such as the fitment of a different filter system or a request to change the power setting of UV lamps, triggers another review.