Daimler-Benz AG, Stuttgart, Germany, has phased out the use of environmentally unsafe solvents in the paints it uses at all of its manufacturing facilities. The company now uses water-based paints. To purify the materials produced during the painting process, Daimler-Benz scientists are testing a plant-based sewage treatment unit at the company's plant in Sindelfingen, Germany. Liquids produced during the painting process are introduced into basins where soil, marsh plants and microorganisms act as purifiers. The raw water cascades freely from one basin to the next in a step-like mode, and subsequently is returned to the production cycle in purified form. The aim is to achieve an entirely closed water cycle for the painting process.