NanoPurification – Development of advanced materials and methods for water and sewage treatment by means of functional nanocomposites
In Germany, tap water is still safe to drink and treated sewage is still released into waters in a clean and purified state. In our affluent society, however, water gets increasingly contaminated by toxic trace substances and drug residues. Multi-barrier systems which do not only clearly filter but also actively degrade the respective trace elements act as barriers both to solid and dissolved substances.
The NanoPurification project focused on developing a hybrid system, NanoPur, which in one process step mechanically retains particulate contaminants and microorganisms and degrades or destroys chemical and biological contaminants. For that specific purpose, composite microsieves (technol. nμ sieves) – i.e. surface-active metallic filters – were combined with a photocatalytic nano titanium dioxide coating and an UV-LED decontamination option. The project results were to intensify relevant processes in drinking water purification, sewage treatment, sewage purification, and product processing.
Wet-chemical coating has proved to be the most suitable among different physical and chemical titanium dioxide coating methods. Whereas maximum degrees of degradation of a test substance (methylene blue) were achieved, most of the investigated coatings proved to be permanently adhesive even under very abrasive conditions.
The composite microsieves were implemented in compact combined modules with a novel LED lighting system, integrated in pilot plants, and bypass-operated in a municipal sewage treatment plant and in waterworks. Although in both cases, good degrees of degradation were achieved for certain trace substances, other micropollutants were not or only insufficiently removed. NanoPur, hence, was not found suitable for trace substance elimination on a larger scale.
A comprehensive review of current studies has revealed that, in spite of its ecotoxicological potential in the aquatic environment, nano titanium dioxide, due to agglomeration and adsorption processes, is converted very rapidly into non-toxic, harmless macroparticles. One of the advantages of NanoPur over most photocatalytic reactors with nanoparticle suspensions is the immobilisation of the nanoparticles on a substrate. In laboratory analyses, no titanium dioxide was detected in the effluent of the pilot plant.
