Permavoid Limited

Permavoid Geotextile Permafilter


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Permafilter Geotextile has been specially designed to retain hydrocarbon pollutants. Permafilter Geotextile comprises non-woven, needle punched geotextile made from a proprietary blend of modified polyester fibres. The textile has a weight of 300g/m². The entrapped pollutants are either removed or reduced to levels suitable for discharge into controlled waters.

Working principle

The proprietary blend of fibres in Permafilter Geotextile exhibit specific hydrophilic and hydrophobic properties and these, combined with the dimpled structure, work together to form multiple layers with inherent oil retention properties. The hydrophobic (repelling) material receives and retains the hydrocarbon pollutants, whilst the hydrophilic (waterattracting) elements simultaneously facilitate water retention resulting in a long-term stable biofilm, which subsequently degrades the entrapped pollutants.

Experimental results

Permafilter Geotextile demonstrated retention of up to 6 l of oil per 10 m². The effluent monitoring showed a maximum discharge of 4.5 ppm* during the first flush and during consecutive rain events only an average concentration of 1.5 ppm.


The range of applications for the Permafilter Geotextile is virtually unlimited in traditional geotextile applications, where enhanced hydrocarbon treatment can be achieved.

Furthermore, it is applicable in many ‘new’ applications where the superior hydrocarbon retention is an indispensable requirement.

Examples for applications using Permafilter® geotextile:

  • Pollution barriers
  • Permeable pavements
  • Impervious pavements
  • Infiltration systems
  • Attenuation systems