GBU Gesellschaft für Brachflächensanierung und Umwelttechnik mbH

Microbial degradation

In tar oil contaminated soils natural degradation processes take place in long periods under anaerobic conditions.

Tar oil and petroleum contaminants in water from soil washing are degradable by aerobic bacteria in significantly shorter periods. The bacteria get their energy by electron transfer from the pollutants towards oxygen (electron transport chain) and the insertion of oxygen in these organic substances by bacterial catalysts (mono-, dioxygenases). In petroleum-derived hydrocarbons oxygen is integrated at the end of the carbon chain, in (polycyclic) aromatic hydrocarbons into the ring system.

Also poorly degradable substances can be activated in this way for the further metabolism. After transformation they become bioavailable. An important factor for the degradation of these compounds is the phenomenon of cometabolism. In presence of easily degradable substances bacteria are able to use the same pathway for the poorly degradable derivates (related compounds). For instance fluoranthene and pyrene are metabolized in the presence of naphthalene much faster. Finally the pollutants will be mineralized to carbon dioxide and water.

Chemical oxidation

In our water treatment plant we also use ozone to accelerate the microbial degradation. Ozone is produced by a combined oxygen and ozone generator. More complex compounds are cracked by ozone and can be degraded in the following bacterial stage. The ozone treatment allows shorter retention time and compensates the absence of cometabolitic substances like naphthalene. This can occur in the process water treatment of multiple washed soils.