Sewage on board ships

Sewage originating from toilet and hospital facilities and greywater from showers, sinks, laundry and galley cause severe damage to the marine environment. Organic pollutants and nutrients can disequilibrate the local ecosystems at the discharge point and thus endanger the aquatic flora and fauna.  

In order to prevent this, the International Convention for the Prevention of Pollution from Ships, MARPOL 73/78 Annex IV, allows the discharge of untreated sewage only under certain conditions after treatment in a type approved sewage treatment plant (STP) meeting the effluent standards under test conditions adopted by the Marine Environment Protection Committee by resolution MEPC.227(64). If ships do not comply with these regulations, they can face fines and detentions by local authorities. 

RWO’s sewage treatment on board ships

RWO Clean Sewage Systems are based on biological treatment processes, ensuring a minimum of chemical consumption and byproducts.  

RWO offers the CS-BIO for merchant vessels or small passenger vessels outside special areas. The treatment principle is based on the biological Moving-Bed Biofilm Reactor technology (MBBR) and serves as an all-in-one solution, integrating the holding tank into the STP, thus occupying less space. The robust design offers stable operation and very low maintenance. 

Operating in special areas (Baltic Sea), it is crucial that passenger ships meet the highest effluent quality according to IMO resolution MEPC.227(64) including nitrogen- and phosphorous- removal (chapter 4.2). Therefore, RWO provides the advanced water purification plant CS-MBR for passenger vessels.

RWO recommendation for STP onboard ships are as follows:

Biological Sewage Treatment maximizing onboard space

Discover CS-BIO

Advanced water purification and advanced wastewater treatment.

Discover CS-MBR

Biological Sewage Treatment maximizing onboard space

Discover Grease Interceptor
Operation Suggested RWO solution 
Merchant Vessels CS-BIO  
Passenger Vessels <12 Passengers CS-BIO  
Passenger Vessels <200 Passengers CS-BIO / CS-MBR depending on requirement  
Passenger Vessels >200 Passengers CS-MBR 
Sewage Treatment Brochure

Leading towards a more sustainable future, our RWO products for marine sewage are fit for treating besides sewage various additional wastewater streams such as gray water from accommodation, laundry and galleys. Thus, our products are compatible with additional environmental class notations such as BV CleanShip, CleanShip Super or AWT-A/B, DNV-GL Clean(Design) and US 33 CFR 159 Subpart E (Alaska).