DNV GL has been investigating the opportunities around recycling wastewater offshore. We have created plans to redesign a tanker that might otherwise be used to carry oil, but which instead can be used as a floating wastewater treatment plant. Called The Changemaker, it is a vessel that turns the wastewater coming from the shore via pipelines into clean water that can be used for irrigation and industry purposes.
The Changemaker would be able to recycle around 2,100 m3 of wastewater per hour, serving upto 250,000 people. It would house primary, secondary and tertiary treatments of the water and also be able to supply large volumes of biosolids which can be used as the basis for fertilizer.
Another vessel - The Reliever - has also been designed to take on the capacity of shore-based treatment plants when they need to be upgraded or repaired. Parts of the energy needs of these offshore wastewater recycling plants can be powered by renewable sources such as biogas, which can be extracted from the treatment process onboard.
The idea of offshore recycling makes economic sense, too. It is estimated that the capital expenditure required to create this offshore wastewater recycling plant over 20 years is around -25 per cent less than for an onshore plant with equivalent capacity.
It is clear that offshore wastewater treatment can be both feasible and profitable, and that it can be applied in most coastal areas around the world. We believe it is a potentially exciting new market that can help tackle a pressing sustainability issue.