Liquid wastes from ships at sea present a potential environmental threat, and their discharge is strictly regulated. But there is growing pressure to make shipping even more environmentally friendly, and DNV is taking part in a joint Norwegian–Singaporean water-treatment project which should further reduce the risk of marine wastewater pollution.
Despite existing regulation, pollution due to wastewater discharge is an issue the maritime industry must face if it is to develop in a sustainable manner. Increased shipping activity, notably in cruising and in oil and gas transport, in protected and environmentally sensitive areas requires ‘greener’ vessels. The industry depends therefore on innovative, simple, robust and efficient water-treatment technology.
Novelty of the approach proposed in the new Norwegian–Singaporean MEMSHIP project lies in the fact that all wastewaters are treated together, in a single treatment system able to tackle the wide composition and properties of all the various wastewaters – black water, grey water, bilge water and wet garbage.
The membrane bioreactor
Membrane bioreactors (MBR) are a state-of-the-art technology combining membranes with biological processes for treatment of wastewater. The furthest developed and commercial concept uses membranes for the separation of biomass with activated sludge (AS-MBR). Advantages include small size, good effluent quality, complete removal of solids from effluent, high loading rates, disinfection of effluent and low sludge production. MBR is mostly used in land-based applications, and adaptation to shipboard use is likely to be necessary for optimal performance.
Combining membrane and bioreactor technologies is expected to increase the quality of treated water, thus promoting schemes to recycle and re-use treated water (so reducing discharge) and so to minimise sludge production. Such treatment plant will reduce the use of water on board, and will potentially affect ship design and operation.
Partners in the project are DNV, the Department of Hydraulic and Environmental Engineering of the Norwegian University of Science and Technology (NTNU), KeraNor AS and, in Singapore, the Institute of Environmental Science and Engineering (IESE Pte Ltd), the Maritime Port Authority and Surbana International Consultants Pte Ltd.
DNV’s role in the project is to ensure that the performance of the proposed treatment plant, in terms of reliability and functional requirements, is suited to shipboard use and that it complies with existing standards and IMO regulations. DNV has defined the composition of four test wastewater samples to be used during the development, optimisation and evaluation of the treatment system. Production of the various wastewaters, depending on ship size and type, has been investigated and the composition of representative test samples determined.
DNV’s participation is an important part of our work in water-quality management, and contributes to building competence in this new technology.
Date: 2006-10-12