Preventing salinisation with the Fresh Keeper
In many areas in the Netherlands brackish water is present underground at shallow levels. In the process of pumping up fresh water, there is a risk that the underlying brackish water will also flow into the well. The extracted water cannot then be simply used as a source for drinking or process water.
The Fresh Keeper maintains the fresh and brackish water in the underground apart. By desalting the extracted brackish water using membranes, one can make further use of it and the salt residual stream can be reinjected into the ground. “The aquifer in which the water is reinjected must have the same saline concentration as the residual stream,” says researcher Klaasjan Raat. “In this way you prevent the discharge of the residual stream from having a negative impact on the quality of the groundwater.”
Pilot projects in Noardburgum (Vitens) and Zevenbergen (Brabant Water) have demonstrated that brackish water extraction is an effective strategy against groundwater and well salinisation. Raat kept a close eye on any changes in underground water quality in both pilots. After two years of reinjecting the saline residual stream, he is assured that the impact of the procedure is limited.
The Zevenbergen pilot is still ongoing. They are currently working on adding carbon dioxide to the salt residual stream so as to prevent the formation of lime deposits in the ground and around the injection well. “In practice, the Fresh Keeper means that salinised drinking water wells can be brought back into operation. The procedure has attracted a great deal of interest, including internationally,” says Raat.
© 2017 KWR Watercycle Research Institute