NanoSAN – A nanotechnological clean up method – In situ use of iron oxide nanoparticles for elimination of harmful substances from abandoned polluted areas
The NanoSAN project investigated the biological in situ bioremediation of groundwater pollution caused by benzene and tar oil using iron oxide nanoparticles (NP). For the first time, the processes observed were validated in a field test.
The high potential of iron oxide nanoparticles regarding the efficient oxidation of toluene and acetate was confirmed in laboratory tests. Due to their better electron availability, the iron oxide nanoparticles achieved much higher degradation rates than aggregated crystalline iron oxides. Laboratory test of nematodes and microbial sediment growth revealed that ecotoxicological side-effects only occur in the nanoparticles injection area. A screening method was applied to identify and select special iron oxide nanoparticles from goethite (also referred to as needle iron ore) which have a high mobility and reactivity in groundwater and are ecotoxicologically uncritical. A specially developed coating with humins allowed for specific adjusting of the mobility and reactivity of the iron oxide nanoparticles. These modified iron oxide nanoparticles were then the basis for a large scale production of an ion-free suspension together with the development of a suitable hydrophysical injection method.
To monitor the success of the clean-up, innovative, reaction-specific isotope analyses were carried out. Besides, the population dynamics of potential pollutant-degrading microorganisms was traced by means of molecular-genetic methods. At certain places and certain time points, a distinctive stimulation of the biological BTEX degradation (BTEX = aromatic hydrocarbons benzene, toluene, ethylbenzene & xylene) could be observed, which was hampered by unexpected negative effects of floating oil-phase.
As was intended, proof-of-principle for the developed method was provided for in situ groundwater bioremediation. To reach market maturity, however, further development and validation steps will be required.
