At the Vitens water production site in West-Terschelling about one-third of the drinking water is extracted from the freshwater aquifer located beneath the Waddenisland. The remaining two-thirds are supplied from the mainland of Friesland via the so-called Wad-pipelines through the Wadden Sea.

The groundwater on West Terschelling contains small amounts of methane, most of which is removed via conventional treatment at the treatment plant. This did not take place in the anaerobic nanofiltration (NF) units until quite recently, resulting in the connected aeration and degassing tower (BOT) requiring frequent cleaning. Also resulting in a bacteriologically less stable water quality, requiring the use of UV disinfection.

Vitens decided to use a small Logisticon pilot plant to investigate methane removal from the nanofiltration permeate via membrane degassing. This innovative technology assures that methane can now be removed from the NF permeate in a very targeted way. The aeration tower now needs much less frequent cleaning, resulting in considerable operational cost savings. Even more importantly, the drinking water’s bacteriological stability has improved significantly, which means that UV is no longer necessary. After this pilot, Logisticon received the order for the construction of the first membrane degassing plant, designed in accordance with the Vitens standard (M/E/PA), with a drinking water capacity of 30 m3/h.

The principle of degassing using membranes relies on the close contact of the water to be degassed with a vacuum and/or gas stream, in which the phases are separated by a hydrophobic membrane. Vitens will probably also use this technology at other production sites where there is a lot of methane in the anaerobic groundwater. This is because the pilot studies have shown that, following membrane degassing, methane gas in groundwater can be optimally used for energy recovery, including converting CH4 to CO2. Whereas methane is normally blown into the atmosphere, this new technology allows Vitens to both generate energy and significantly reduce its carbon footprint. The study also showed that the underlying purification processes functions much better following methane removal from the anaerobic groundwater. 

Yet another great example of the opportunities created by the collaboration between water company Vitens and Logisticon Water Treatment.