The proven remediation technique for hydrogen chlorides
In the metal industry and in chemical sanitation, frequent use is made of chlorinated degreasants and solvents (VOCl: volatile organochlorines), such as Per and Tri, because of their excellent degreasing characteristics. A disadvantage of these substances is that any leakages will lead to substantial soil contamination. Stimulated biological degradation of contaminants offers opportunities to remediate large-scale contaminations in a cost-effective way.

HMVT has developed a remediation concept for VOCl contamination – ENNA. ENNA is short for Enhanced Natural Attenuation. The principle of ENNA is that maximum use is made of the bacteria that naturally break down contaminants. By letting nature do its work, remediation using the ENNA concept is considerably less costly than other remediation techniques.

How does it work?
ENNA involves the one-off injection of a special substrate into the soil. This substrate consists of a mixture of vegetable oil and various additives that ensure that the nutrients are gradually released over a very long period in a slow-release process. This allows the bacteria to break down the contaminants in the soil over a period of some 5 to 10 years.

  • Step 1: creating cracks
  • Step 2: injecting ENNA

Source or plume approach
ENNA can be applied in source areas or in plumes. In conjunction with natural degradation, the contamination will shrink or fade over time, resulting in a stable end situation.

ENNA can be applied in the plume as well. Injecting the ENNA substrate into a row of filters perpendicular to the groundwater flow creates a zone in which the contaminants are broken down (a biobarrier). In short, ENNA can be applied:

  • in the source zone
  • in the plume
  • as a control measure
  • in conjunction with other techniques such as chemical oxidation, groundwater extraction, reduction using zero-valent iron, thermal techniques, excavation and acoustic remediation.

Injection units
HMVT has developed and built various injection units for the injection of substrate. The unit used depends on the amount of substrate that we inject.