These pollutants get into the biological purification plants and cannot be eliminated by the microorganisms there. Using the sun as light source, the photo-catalytic sewage treatment is capable to change pollutants dissolved in the water through photo-chemical oxidation. The prosys° GmbH from Bremen has developed a procedure of chemical wet-oxidation - and had it patented - that works without the use of chemicals. Thereby, a dye used as catalyst is transferred into an energy-intensive form by absorption of visible light. The dye transfers this energy on the oxygen dissolved in the water, that, in its energetically higher form as Singulett-Oxygen, then deteriorates the pollutants.

The prosys° GmbH advanced the procedure of the photo-catalytic water treatment to market maturity. Its effectiveness in the technical standard has been confirmed on the basis of phenol - and PAH-containing groundwater. The procedure was also applied in the shipyard area with the purification of TBT-containing effluents. Compared with conventional procedures, the photo catalysis is an extremely attractive resource-saving and economical alternative. The innovative prosys° procedure received the Bremen Environmental Award in 2005.