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Solving the aftpeak tank ballast water challenge

oneTANK has developed a small scale innovative, low-cost, IMO Revised G8 Code and United States Coast Guard compliant system.

ERMA FIRST now has an additional ballast water treatment solution system in its portfolio, specifically designed to be run alongside its larger electro-chlorination systems (FIT) or as a standalone aboard smaller vessels such as workboats and superyachts. oneTANK is a chemical in-tank system with a tiny footprint which can be used in a larger vessel’s aftpeak tank to provide salty feedwater for electrolytic based cargo body ballast water treatment systems.

Treating ballast water from a tanker’s aftpeak tank in a compliant and cost-effective way causes many ship operators challenges. By regulation, the water cannot be mixed with the cargo body ballast water, due to the risk it gets contaminated by oil from an adjacent leaking cargo tank. This would be an explosion risk. So, it needs a separate ballast water treatment system.

With little space available for a system near the aftpeak tank, companies will often choose a smaller version of the same ballast treatment technology already selected for the cargo body ballast tanks. But there are more efficient ways to manage ballast water from lay-out, operational and cost perspectives.

This July, leading ballast water treatment system manufacturer ERMA FIRST acquired oneTANK, a subsidiary of US naval architecture and marine engineering firm Glosten. oneTANK has developed a small scale innovative, low-cost, IMO Revised G8 Code and United States Coast Guard compliant system.

This technology is now available globally and can be installed in larger vessels’ aftpeak tanks. It is also suitable for use aboard workboats, tugboats, semi-submersibles, fishing vessels and superyachts. The technology is already being adopted on ships in aftpeak tanks within Overseas Shipholding Group’s tanker fleet and on the dredger MV Charlock in the Netherlands.

The system is a game-changer: it can run alongside cargo ballast tank systems onboard large ships and brings a cost-effective, practical solution for smaller vessels struggling to comply with stringent ballast water regulations.

So how does it work?

What sets oneTANK apart from other systems is its simplicity: it uses chemical in-tank treatment and nozzle mixing. There is no need for filters, backflush pumps, UV lamps, clean-in-place units, hydrogen gas safety and venting. There are no transformers, rectifiers, flow meters, and no control valves. It really is ballast treatment simplified.

A 24 hour hold time is required. At around 9 hours, oneTANK checks and confirm adequate residual oxidant. If the water quality is poor, more chemical will be added to ensure proper treatment. This is a major advantage of the in-tank approach, both eliminating the filter and ensuring treatment even in poor water quality.

When ready to discharge the aftpeak tank, the operator simply selects ‘start neutralisation.’ oneTANK starts the circulation pump and automatically adds the neutraliser, sodium thiosulfate. In about one-hour, the tank is ready for discharge or use as salty seawater feed for electro-chlorinisation based cargo body ballast water treatment systems such as ERMA FIRST FIT.

Its footprint is only 600mm x 600mm, half the size of its nearest competitor. Its power consumption is similar to that of a household washing machine. With low-running costs and fully regulatory compliance, oneTANK provides a ballast water management solution which works in all water qualities and salinities.

The system uses an 8.25% or 12.5% sodium hypochlorite (bleach) and 30% sodium thiosulfate solution – readily available chemicals that can be purchased from suppliers worldwide. Application is practical for smaller vessels as a 20-litre container of 12.5% bleach will treat approximately 288 cubic meters of ballast water. For larger vessels, oneTANK can treat tanks as large as 4,000 cubic meters.

Seawater is automatically treated by applying and mixing the bulk chemicals in-tank, allowing users to treat on their own schedules, avoiding busy in-port times.

Is it environmentally friendly?

There are two environmental concerns associated with the use of any chemicals in treating ballast water: active substance and disinfection by-products.

oneTANK treats water by raising the total residual oxidant (TRO) level in the ballast water tank to an average of 5 mg/L for at least 24 hours. This ensures effective treatment of the ballast water and associated piping. The same in-tank treatment process neutralises the active substance to less than 0.1 mg/L BEFORE the ballast water can be discharged. This ensures that the receiving harbour does not receive any significant active substance. For perspective, the World Health Organization recommends at least 0.5 mg/L at drinking water taps.

The technology also underwent significant testing for disinfection by-products in accordance with guidance from the International Maritime Organization. This data was assessed and reported to the IMO’s scientific body (GESAMP) by DNV as the Independent Laboratory. GESAMP found that the technology did not form excessive disinfection by-products.

A small, simple system is also a sustainable system. oneTANK uses no exotic materials, no filtration, no transformers or rectifiers. It uses little steel and weighs only 216 kg, meaning that its shipping footprint is low. Its operating costs are low thanks to its low energy consumption. Low power means fewer integration points and reduced cabling. At the end of its life, the system is recyclable as it does not contain exotic materials, alloys or complex electronics.

For further details please visit:

Exhibitor: ERMA First

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