How the installation of a new wastewater system on Celebrity Silhouette was a unique refit
RWO has successfully installed its new CS-MBR – a sustainable wastewater treatment system – on Celebrity Silhouette while the ship was still in operation.
The unique refit took place in April this year when the company upgraded an existing installation to the CS-MBR standard. This involved installing new dosing equipment and mixers, replacing the aerators in the membrane tanks and bioreactors along with the membranes themselves, and installing new screens with a smaller mesh size.
RWO area sales manager Valentin Kirsch commented, “The vessel was in full operation during the upgrade with nearly 2,800 passengers. The sewage treatment system needed to be in operation the whole time, so we had to do the upgrade while it was operating and ensure the treatment system was functional.
“That was the most challenging part of the upgrade. This was pretty unusual as normally this kind of extensive upgrade is done in drydock.”
RWO had to carry out the upgrade step by step. Mr Kirsch says, “We upgraded the bioreactors one by one, before moving onto the first membrane reactor. We had to follow a sequence to allow 50% of the system to operate at all times - even at a little over design capacity - so if one reactor was out of operation, the rest of the system was still able to operate and compensate for the reactor that was being upgraded.”
Mr Kirsch says the company has received several inquiries about upgrades, but this is the first large one they have done while the ship is in operation.
The upgrade was to ensure the ship met the latest Marpol regulations for wastewater in the Baltic Sea, which stipulates passenger ships operating in the special area must have a sewage treatment system that is compliant with IMO MEPC.227(64), including chapter 4.2 for nitrogen and phosphorus removal.
He explains, “Most customers did not have such requirements in the past. Passenger ship operators currently only need these high standards if they want to operate the vessel in the Baltic Sea. This is currently the only area with restrictions on nitrogen and phosphorus.”
It was a race against time to get Celebrity Silhouette’s wastewater system upgraded in time for its Baltic Sea cruise. Mr Kirsch explains that the issue was with the logistics.
“Global logistics nowadays are a mess. The plan was to do the upgrade in the US, but the equipment needed for the upgrade was delayed significantly and arrived when the ship was en route to Europe. This led to a delay in starting the project, so time was ticking, and the time window was closing fast.
“In the end, we used equipment that had been prepared for a sister vessel’s upgrade in Europe later in the year. Celebrity Cruises was happy we were able to deliver the equipment in time for Silhouette arriving in Europe. This meant the project was finished just in time to hand over a fully compliant system for the Baltic cruise.”
RWO’s upgraded system for Celebrity Silhouette has ultrafiltration membranes, which without any additional treatment process, can remove over 99% of solids from sewage, including microplastics.
Mr Kirsch highlights the benefits, “The major benefits from this type of system is it is not just complying but over-complying, as I am sure microplastics will be a topic in future regulation. This system is 10 years into the future.
“Cruise companies want to have a green policy and the right way to go forward is by not just following but over-fulfilling requirements. The vessel is then future-proofed for whatever requirements come next.”
