One of the focal research points of the Department Environmental Engineering is the development of new methods for water clean-up. With Carbo-Iron, a new in-situ reagent for groundwater treatment is presented. The combination of colloidal activated carbon and supported nano-structures of zero-valent iron (10-25 wt-% Fe) gives a new environmentally friendly reducing agent. It opens up pathways for plume control in aquifers contaminated with halogenated organics because of the high particle mobility in porous media which is a pre-condition for the generation of a wide in-situ sorption/reduction zone. In addition, the material is suitable for source remediation because of the hydrophobic nature of the composite material which provides the basis for a high particle-DNAPL affinity. As known for zero-valent iron, Carbo-Iron is also able to reduce a broad spectrum of halogenated hydrocarbons. The composite material is moreover able to utilize the sorption active activated carbon support for collecting the hydrophobic pollutants which are available for destruction at the reducing agent iron. This makes the material especially suitable for the clean-up of low-concentration water contaminations in the µg/L and mg/L range as common for polluted groundwater. Carbo-Iron is quasi the better alternative to nano-iron.