Answering the cruise operators' call for sustainability

Water treatment specialist RWO shares how technologies are enabling green travel

Answering the cruise operators' call for sustainability
Cruise operators can conveniently upgrade their existing advanced water treatment systems to the new CS-MBR standard

By Lars Nupnau |

Ensuring that customers can sail safely and confidently is a top priority for cruise operators in the wake of the Covid-19 pandemic. Many are also increasing investments in green technologies to meet growing customer demand for sustainability too.  

A survey published by global travel agency network Virtuoso in April 2021 found that 82 per cent of respondents wanted to travel more responsibly in the future, with 70 per cent agreeing that sustainable travel enhanced the experience. Half of respondents ranked a strong sustainability policy as “very important” when choosing a hotel, cruise line or travel company.  

Ship emissions represent a central consideration for cruise lines, where responding to informed consumer choice is increasingly a driver for sustainability strategies, alongside compliance and reputation. Today, guests wish to play an active role in environmental protection, whether through responsible towel laundering, recycling or investing in reusable water bottles. 

Sewage, however, is one environmental factor that falls outside the purview of personal choice because protecting oceans from the impact of cruise ships is best left to regulators. After all, it is estimated that the average cruise ship with 3,000 people onboard will generate around 30,000 gallons of sewage a day (excluding grey water). That is over 200,000 gallons on a week-long cruise.  

Also referred to as black water, sewage contains a myriad of hazardous pathogens, bacteria, viruses and chemical nutrients that are harmful to human and marine life. Hence, the International Maritime Organization (IMO)MARPOL Annex IV regulation prohibits sewage from being discharged into the sea unless the ship has an approved sewage treatment plant in operation, or the sewage has been broken down and disinfected using an approved system at a distance of more than three nautical miles from the coast.  

However, the 2016 resolution MEPC.227(64) introduced Special Areas and entirely prohibited the discharge of sewage from passenger ships within these areas unless the vessel has an approved sewage treatment plant that also removes chemical nutrients.  

Chapter 4.2 of the resolution states that if a vessel is intending to discharge sewage effluent in special areas, the treatment system must meet the nitrogen and phosphorus removal standards. 

The Baltic Sea is currently the only special area under these regulations, which applied to all new and existing passenger ships operating in this area as of 2021. However, from 1 June 2023, restrictions will apply to “existing passenger ships en route directly to or from a port located outside the special area and to or from a port located east of longitude 28˚10' E within the special area that do not make any other port calls within the special area”. 

RWO, a supplier of intelligent water management solutions, suggests it is fair to assume more areas will come under the regulations as pressure to protect the world’s oceans from pollutants continues to grow. 

Today, cruise lines that see environmental protection as a priority, or are operating in the Baltic Sea, can either install an advanced wastewater treatment system (AWTS) or hold treated sewage onboard. 

RWO recently launched its new generation AWTS, with first installations taking place onboard two of Celebrity Cruises’ Solstice-class vessels – Celebrity Silhouette and Celebrity Reflection. The installations will upgrade the vessels existing RWO MEMROD sewage treatment plants in preparation for the regulation changes in 2023. Type approved in accordance with IMO MEPC.227(64) including chapter 4.2, RWO’s CleanSewage Membrane Bioreactor (CS-MBR) is a sustainable biological treatment technology that has been designed to minimise a vessels impact on the environment. 

Customisable to individual requirements, the CS-MBR treatment process uses a unique submerged membrane design in the final separation stage. This not only results in water that is disinfected, clear and free of solids, but also increases energy efficiency, enables a compact design and reduces maintenance requirements, making it easier to operate. The water is also pure enough to be reused for other functions such as laundry, or as technical water. 

Membrane technology will be a game changer for the cruise sector. Membranes remove over 99 per cent of solids, including microplastics and viruses, which enhances water purity and prevents diseases. 

As the recent COP26 gathering showed, expectations for sustainability will only continue to rise. In an increasingly digital and connected maritime industry, RWO is also working alongside partners including TUI Cruises and Hanover University in support of the cross-industry OSCAR research project. Funded by the German Government, OSCAR is researching online modelling, simulation and remote-controlled systems for onboard environmental technologies on cruise ships.  

Scientists from the Institute of Sanitary Engineering and Waste Management are developing and testing digital twins for AWTS using a smaller version of RWO’s CS-MBR system. The aim of the project is to design a digital twin that enables ship management companies to simulate the AWTS of a cruise ship onshore using data from the vessel, to support crew and provide advice or guidance where required. 

Lars Nupnau is business development manager at RWO 

This article was first published in the Spring/Summer 2022 issue of Cruise & Ferry Review. All information was correct at the time of printing, but may since have changed. 

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