Alternatives to onboard ballast water treatment are often seen as contingencies, but shore-based ballast water treatment can be an elegant solution in the right circumstances
Bawat chief executive Marcus Hummer and Glosten director of research & development Kevin J Reynolds discussed ballast water treatment alternatives during the Niche solutions and decarbonisation of ballast water treatment systems (BWTS) webinar, sponsored by Bawat and part of the Riviera ballast water webinar series.
In the world of ballast water treatment systems, the technological approach by Bawat is now almost unique. According to Ballast Water Treatment Technology’s database of ballast water treatment systems, only one other system uses heat as a source of treatment, but only Bawat’s has achieved US Coast Guard and IMO revised G8 type-approval.
Mr Hummer explained the advantages of the Bawat approach, “Traditional (UV or electric chlorination) ballast water management systems works in a two-step process,” he said. “The (Bawat) ballast water system works as a single-pass ballast water management system.”
“You take untreated ballast water, either directly from the sea or from a ballast water tank, in a single pass through the Bawat system. You have D-2 compliant ballast water to take into the ballast water tank or flush on board. That single- pass system offers an enormous amount of operational flexibility,” he said.
As mentioned above, the Bawat system uses heat. In fact, it uses heat and time to pasteurise the ballast water. “On board vessels, we take heat, normally from the cooling water from the main engine, and the time aspect for the pasteurisation is through a retention section, where we slow down the continuous flow,” explained Mr Hummer.
The ballast water is heated to 70oC and retained for 40 to 60 seconds to reach the required level of pasteurisation for D-2 compliance.
“We are often met with a question: can you then put 70oC water back in overboard or into a ballast tank? Of course, we do not do that. We use the heat from the treated water to preheat the water coming into the system. Thus, the outlet temperature of the treated water is only a couple of degrees warmer than the water that we took in,” he explained.
The heating section and the preheat section uses heat exchangers, similar to those used on board many ships in the engine space. “What we do not have,” said Mr Hummer, “is a filter, because with pasteurisation, we do not need a filter for our system. That gives an enormous amount of flexibility.”
There is an additional benefit, “The system runs on waste heat, so there is practically zero opex with our system,” he said. The question of opex can be answered easily. “The only opex is for a little bit of electricity to run the designated ballast water pump,” said Mr Hummer. On the capex side, the Bawat system has heat exchangers, which is balanced to some extent by no capex on filters. On opex, crew will be familiar with the maintenance of heat exchangers.
How important is the total cost of ownership, capex, and the carbon footprint of a ballast water treatment system? In a poll, 48% ranked their items in order: capex, total cost of ownership and carbon footprint. Another 33% ranked the order of items as total cost of ownership, carbon footprint, and then capex. None of those surveyed ranked carbon footprint ahead of the other options.
Turning to the second theme of shore-based ballast water treatment systems, the Bawat system has been adapted to fit in a shipping container. Mr Hummer said, “It is very simple to containerise and make mobile. We can add a heat source to it, then we have the perfect solution for contingency service in ports and terminals.”
The system can react rapidly to ships that arrive in port with no ballast water treatment system, or one that has an inoperable system. This is also a solution for barges that have no ballast water treatment system – the Bawat system is agnostic of water quality – there is no filter to black and backwash and no UV lights that might struggle with high-silt river water.
According to a poll, the demand for a mobile solution is lower than permanent shipboard installations: 22% responded in the positive for a mobile solution, with the remaining 78% not requiring a mobile solution as an option.
The newest mobile solution on the market is the Glosten-developed oneTank ballast water treatment system which was awarded US Coast Guard type-approval in September 2020. Mr Reynolds explained that starting in 1999, Glosten was one of the first marine engineering companies to tackle ballast water treatment and began developing a containerised system in 2008 and produced a system for articulated tug barges in 2014.
Mr Reynolds has been working on ballast water treatment system developments since 2001. “We developed the oneTank system based on the Envirocleanse inTank system to treat the water in a tank,” said Mr Reynolds. The chemical is introduced into the ballast water in the tank and then circulated through the ballast water tanks.
“The oneTank unit is very small. It takes a little bit of water through the existing piping system, circulates it through the oneTank system, back into the tank, then treats it with some bulk chemical,” said Mr Reynolds. “Ballast water is now laden with the chemical, it then exits out the nozzles into the ballast water tank. The water that returns through the piping now has the chemical for the TRO analyser on the oneTank ballast system to detect that chemical.”
About halfway through the 24-hour hold time, the ballast water is treated with a second dose of chemical. The advantage is that the unit has a small footprint and can be supplemented with an additional pump if required.
This is an advantage for vessels that have tanks in the aft peak, where it would be an expensive option to add a retrofit ballast water treatment installation. A low footprint, highly transportable unit like oneTank might be the solution. “There is not a need for a system that is capable of treating the entire ship just for that aft peak. We can use this very simplified technology for that aft peak tank application. One of our customers estimated a cost savings of over US$100,000 as compared to using a full-flow discharge treatment system for that aft peak tank alone,” explained Mr Reynolds.
Another niche sector is workboats and fishing boats with ballast tanks. These generally work and ballast in the same area and treatment is not required. However, a transit voyage requires ballast water to be treated and it is too expensive to retrofit ballast water treatment for these rare voyages. A system like oneTank fits the role.
In this respect, both Bawat and oneTank are suitable for those vessels with limited space and a less frequent need for ballasting, such as the offshore sector. In the US offshore sector, the vessels are in the same risk zone. A voyage outside the risk zone might require one or more ballast tanks to be treated, for which it is difficult to justify a full onboard system, but a niche product such as Bawat mobile or oneTank is an elegant solution.
Bawat BWMS case study: heavy lift vessels
Bawat’s chief executive Marcus Hummer explained the role the Bawat ballast water management system plays in the case of a heavy lift vessel installation. A heavy lift vessel has a very high demand on the ballast water system during cargo operations. A ballast water treatment system capable of meeting those demands would require high capacity flow rates and even then, might be prone to causing interruptions to cargo operations at crucial moments. The Bawat solution was to install a ballast water treatment system that can be decoupled from the main ballast water mainlines.
“The Bawat system comes with its own smaller designated ballast water pump that is suited to treat the ballast water during transit. That means there is no use of the ballast water management system during cargo operation,” said Mr Hummer. “There is a much smaller footprint for the ballast water management system installation and thus a much smaller investment.”
In a poll, over three-quarters of respondents agreed that being able to decouple ballast water treatment from cargo operations would have a significant or highly significant impact on preventing delays to cargo operations.