With the UN predicting a global water shortage of 40% by 2030, solutions offering alternatives to harnessing water table resources are becoming vital. In addition to seawater desalination and wastewater treatment, the use of submarine freshwater sources looks very promising. This is the ground-breaking approach adopted by Marine Tech, a French firm specialised in innovative technologies for marine environment challenges. Its engineers have developed an original exploration and production solution for these previously untapped reserves, which they will be presenting in a few days alongside SUEZ at the IDA World Congress, which will bring together desalination experts from 30 August to 4 September in San Diego, California.
Tapping submarine drinking water sources, which can be found in all the seas around the world, is not a new development. This can be seen with the remains of the water catchment systems developed by our ancestors and discovered in the Eastern Mediterranean or Persian Gulf. As Marine Tech explains, in most cases these are former terrestrial springs that were formed several thousand years ago when sea levels were lower than today. They can be found in regions where coastal geological formations are made up of limestone or volcanic rock. Driven by gravity, the water seeps through these rocks and naturally flows towards the lowest point, often below sea-level. Less dense than salt water, the freshwater that emerges from the seabed is more buoyant and rises to the surface. Marine Tech makes use of this natural “driving force” to detect and recover the freshwater.
The “Tulipe” technology. Credit : Marine Tech
Marine Tech has developed a specific method and specific resources for exploring sources, based around three phases. The first is focused on geological and then thermographic research, aiming to analyse and build up a clear picture of geological conditions in the areas being studied in order to target the most promising springs using satellite observations and airborne thermographic measurements. The second phase involves identifying deposits on the seabed. To do this, Marine Tech deploys a research ship or its own submarine drone – Remote Survey Vehicle or RSV – with salinity probes, acoustic measurements and latest-generation robots to detect the exact location where the water emerges from the seabed. In the third and final phase, a comprehensive review of the source is carried out using a dedicated structure to cap the spring. For several months, the various physical and chemical parameters (flow rate, salinity levels, etc.) and their changes over time are analysed.
Once a promising spring has been identified, Marine Tech taps it using natural energy (buoyancy, hydraulic head, and gravity). In this way, the water is captured without any pumps or electricity, generating zero pollution and greenhouse gas emissions. Moreover, since there is no pumping, the aquifer is not disturbed. According to Marine Tech, its units are located as close to the seabed as possible to avoid disrupting navigation and are designed to withstand several decades of marine constraints, such as swells and currents. Ensuring optimised costs and sustainability, it provides resources that can be used for agriculture, industry and drinking water networks in water-stressed countries.