What lies beneath?

What lies beneath?

Researcher and conservationist Jacques Cousteau is quoted as saying, “For most of history, man has had to fight nature to survive; in this century he is beginning to realise that, in order to survive, he must protect it.” Greater enforcement of marine legislation and the latest technologies to treat ballast water and wastewater are beginning to help vessels do just that.

Text: Richard Orange Photo: iStock & Wärtsilä

Ships today may get away with water pollution on a scale that would never be allowed on land. Some dump large quantities of human effluent into the sea after treatment that often comes down to little more than dilution. Container vessels suck up plant and animal life every time they take up ballast water, and then they release it on the other side of the world, introducing alien species that can devastate local ecologies. Thankfully, this is starting to change. With new regulations in both areas, it will be imperative that ship owners install type-approved water treatment systems to remain compliant.

BWM in action

On 8 September 2017, the Ballast Water Management (BWM) convention will finally come into force, 12 years after it was agreed. From that day, every ship above 400 gross register tonnes (GRT) will have to install a type-approved ballast treatment system at its next mandatory International Oil Pollution Prevention (IOPP) survey.

That means an estimated 34,000 new ballast water management systems will need to be installed over five years, a market estimated at EUR 12–13 billion.

“It’s quite competitive. There are a lot of people who have entered the ballast market because the opportunity appears so big,” says Joe Thomas, Wärtsilä’s director of Ballast Water Management Systems. “We want to be a leader, and be the supplier of choice for our customers.”

Thomas estimates that Wärtsilä’s Aquarius range of ballast water management systems already has some 50+ type-approved rivals. But unlike the competition, Wärtsilä offers both an ultraviolet (UV) treatment solution and an electro-chlorination (EC) treatment solution.

“Our approach from the very beginning was to offer technology choice, to accommodate customers generally having a range of ships in their fleets,” Thomas says.

The Aquarius UV system is most economical for ships whose ballast pumps have a capacity of up to 1000 cubic metres per hour. It uses ultraviolet light to kill bacteria, viruses and other microorganisms.

For ships whose ballast pumps have a capacity above 1500 cubic metres per hour, the Aquarius EC system is more cost-effective. It generates sodium hypochlorite (a disinfectant) from the sea water during uptake and injects this back in to treat the ballast water that is pumped into ships’ ballast tanks. The disinfectant breaks down naturally over time, but to make sure discharges comply with the International Convention for the Prevention of Pollution from Ships (MARPOL) limits, ballast water is neutralised with sodium bisulphite if necessary before discharge.

Both the UV and EC systems share the same automatic backwash filter system, which removes larger organic life and sediments before treatment, and they have similar control systems, making it easier for ship owners to manage spare parts, crew training and the like.

Perhaps Wärtsilä’s greatest advantages lie in its established network of global service centres.

“There are not very many of our competitors who can give the level of global support that Wärtsilä can provide,” Thomas points out. “I would say Wärtsilä is head and shoulders above many of our competitors in this respect.”

Wärtsilä has aimed to make the system as simple and robust as possible. There is no mechanism for assessing the quality of incoming seawater and then varying treatment accordingly.

“It’s ‘on’ or ‘off’, and in that sense, the system is more robust and reliable,” Thomas argues. Instead Wärtsilä has fixed the dose of UV and disinfectant at a sufficiently high level that it will perform as required by regulation.

All of our Wärtsilä Aquarius BWMS are built, tested and commissioned in house
All of our Wärtsilä Aquarius BWMS are built, tested and commissioned in house.
      
Wärtsilä sewage treatment plants are compact and modular in design.
Wärtsilä sewage treatment plants are compact and modular in design.

   

Treating Wastewater

When shipping inspectors from one of the world’s leading maritime states recently carried out a spot check of ship wastewater treatment systems, they confirmed the worst: the onboard sewage treatment plants on most vessels they checked were discharging virtually untreated raw sewage.

The photographs they took of plastic bottles filled with dark brown discharge powerfully illustrate the near complete failure of the International Maritime Organization’s MARPOL Annex IV to protect seas and coastlines from ships’ sewage pollution.

“It’s really astonishing to see how superior the sewage discharge limits appear to be on paper, while at the same time, how bad the reality gets,” says Dr Wei Chen, Future Programme Development Manager at Wärtsilä Water Systems.

According to Chen, this is because the MARPOL Annex IV has no performance verification or compliance monitoring. All that is required is for each vessel to have a type-approved plant on board.

It is only in Alaska, where environmental authorities come on board vessels and take samples of the wastewater about to be discharged, that cruise ships have installed Advanced Wastewater Treatment (AWT) solutions, with the majority of vessels discharging in Alaskan waters using Wärtsilä’s Membrane BioReactor System, which can treat both black and grey water.

The system consists of two pre-filtration units, a bioreactor and ultrafiltration membrane modules to produce clean water and concentrated sludge, which is dried and either incinerated or offloaded in port.

Although the multi-stage treatment is complicated, Wärtsilä has designed the system to be easy to operate and maintain.

Some cruise ships operating in the Baltic Sea already use AWT voluntarily, but section 4.2 of the Marine Environment Protection Committee (MEPC) resolution 227(64), which comes into force in June 2019 for new vessels and in 2021 for existing ones, is likely to increase demand so long as it is properly enforced.

“AWTs have been a true revolution for the cruise sector,” Chen says. “However, in the context of Baltic Sea, it is often forgotten that AWT only existed because Alaskan regulators do enforce their rules. The moment enforcement is taken away, corners are cut.”

There are already signs this might happen. At least one of the sewage treatment plants (STP) approved to meet the new Baltic nutrients requirements purports to remove phosphorus without producing solid residues.

“This cannot possibly be true. But this STP is type-approved and ready to serve to ‘protect’ the Baltic Sea,” Wei says.

There is a similar problem with the latest MEPC guidelines limiting the use of dilution in sewage treatment, which entered into force in January 2016. Most existing STPs have no flow metres installed to make checking compliance possible. Some even add untreated grey water to the last stage of the process.

“It so far has failed,” Chen argues. “For STPs certified to dilute, Qi and Qe [the volume of sewage flowing into the system and treated water out] are not actually made visible to operators or inspectors, making it impossible to verify conformity on board.”

Wärtsilä’s Super Trident STP, which has been refined over four decades, does not use dilution. It instead uses the activated sludge system, which accelerates natural processes, together with chemical disinfection. Unlike most other type-approved STPs, it has a dechlorination stage.

The plants are controlled automatically, saving on crew time and reducing maintenance requirements.

Wärtsilä BWMS being tested at sea.
Wärtsilä BWMS being tested at sea.
Aquarius Ballast Water Management System.
Aquarius Ballast Water Management System.


Further Reading:
Ballast water management systems

The right fit


 

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