Pollutants can be deleted from groundwater by perstraction. Different techniques have been patented. The oldest one has published in 1990 and the youngest one in 1998. In the 2000s has been done few patent applications but no granted patents.
Organic compounds through a membrane has been concentrated from groundwater. The concentration factor is from 1 000 to 10 000 bringing 0.1 ppb concentrations to between 0.1 and 1.0 ppm. Besides the concentration of a contaminant has been analyzed in real-time. The membrane is polymer like polysulphane. The hole diameter is 300 µm and thickness is 30 µm.