Testing the permeability of landfill membranes

 

The geomembrane used to line landfill sites must be in compliance with the permeability requirements laid down by the EU's Council Directive 1999/31/EC of 26 April 1999 on the landfill of waste

A landfill liner is a low permeable barrier which is laid under landfill sites. Until it degrades, the liner, or geomembrane, will retard the flow of leachate and any toxic constituents, into underlying aquifers or nearby rivers, preventing spoiling the local water.

Testing the material for a landfill liner has traditionally been a long, complex and expensive task.  Not only does it need to be a barrier against water and water vapour, but also it needs to act against methane, CO₂ and a host of other gases and petrochemicals.  Unfortunately all of these gases react differently to each material or geomembrane, and a product that is highly effective against some of them may virtually useless against another.

For example PVC is around 25 times worse as a barrier to Carbon Dioxide than it is for Nitrogen.

We have introduced a new version of our highly sensitive permeability measurement system instrument that can measure this characteristic of a material for almost any common gas.  In some circumstances it can even measure these all at the same time.

The requirements of a landfill site are

• a low permeability mineral layer (e.g. a liner or geomembrane)
• attenuation by surrounding geology /hydrogeology

The boundary of the entire geological barrier establishes the acceptable extent of a zone of attenuation below and around any landfill site. Beyond the boundary the potential risk to groundwater and its associated receptors has to be prevented. This boundary is, effectively, analogous to a compliance point, beyond which the requirements of the Groundwater Regulations 1998 must be met.

The equipment is fast, sometimes taking just 30 minutes to give accurate and repeatable results. The equipment is highly sensitive, simple to use and provides automated computerised control.  It is accurate in the PPM range for most gases and in the PPB for some.

Versaperm equipment used to check the permeability of landfill lining membranes

The system is unusual as it can measure anything from thin films to composite structures as well as seals and joined membranes.

Click here for a press release on permeability testing for the liner membranes of land fill sites.

Chick here for the UK Environmental Agency's Landfill directive

Click here for information on Landfill sites from Wikipedia

Click here for the UK Government information leaflet on Earthworks in Landfill Engineering

Click here for Eurocode 7 (EC7) website on geotechnical design