Since 2012, the Mercedes-Benz plant in Bremen has been running a research project involving the purification of waste water using planted ground filters.
In the Bremen plant's bio filter, rain water seeps through a number of layers consisting of gravel, sand, substrate, and compost. This mechanically filters the water and purifies it by means of chemical and physical processes.
The filter has been planted with irises, purple loosestrife, reed canary grass and thoroughwort. This promotes biological degradation because the roots are home to more microscopic organisms that can break down the organic pollutants.
The ground filter, which covers approximately 100 square meters, was set up almost three years ago.
The second phase of the project began in March 2014. Three tanks were set up with a structure that corresponds to the structure of the ground filter. The tanks have different contents, with two planted and one unplanted. Vegetable charcoal was also added to one of the tanks. Vegetable charcoal encourages the growth of fungi, absorbs many harmful substances, supports the micro flora and improves the aeration of the soil. With the help of this test equipment, by 2016 the researchers want to research whether the addition of vegetable charcoal can actually lead to greater filtration of pollutants.
A 30 percent reduction in sediment and suspensions such as ammonium and nitrates has already been identified.
With this project in Bremen, Mercedes-Benz is supporting research into improving water quality. The cost-effective water purification concept is also to be implemented at other locations.