Groundwater research and innovation

As part of this project, the effectiveness of a so-called constructed wetland for purifying water contaminated with heavy metals is being investigated. This is an artificially created wetland from the contaminated groundwater on the premises of GRILLO-Werke AG, which is overgrown with specific plants. An office space was converted into a greenhouse for growing young plants. More precisely, the plants are grasses (Phalaris arundinaceae), which are able to absorb certain heavy metals through their roots and store them in their biomass. By harvesting these plants, the pollutants are removed. After harvesting, the plants simply continue to grow until the next harvest. Ideally, they can be harvested three times a year. The approximate zinc uptake of Phalaris arundinaceae is 10 kg of zinc per hectare per year. The aim of this project is to purify the water step by step. This process of plants extracting pollutants from the soil is also known as phytoremediation, while the extraction of metals from plant ash is called phytomining.

This project is being implemented on a trial basis using IBCs (1m³ water canisters). These were opened at the top and first filled with a drainage layer of gravel and then a layer of sand. The whole thing is then flooded with a mixture of tap water and groundwater.

Three different experimental approaches are carried out in parallel:
1. an experiment with pure tap water
2. a test with a zinc concentration of 10 mg/l
3. a test with a zinc concentration of 20 mg/l

Project 2: Phytoremadiation:

Phytoremediation – also known as phytoremediation – is an environmentally friendly technique that uses plants to clean contaminated soil or groundwater by absorbing pollutants.
Three trial fields with a total area of around 80 square meters have been set up for a project on our GRILLO site near the Willy-Brandt-Ring. The aim of this project is to investigate how heavy metal concentrations change in the leachate. This is to be reduced in the leachate by the plants absorbing it through their roots.

The sward was first removed from two of the three trial fields. The prepared plants (Phalaris arundinaceae and Festuca arundinaceae) were then planted on the prepared areas. These plants should absorb the heavy metals dissolved in the soil or seepage water via their roots and store them in their biomass. This is tested with so-called suction candles. Sucker plugs are slender cylinders about 30 cm long and are used to remove soil water. They are inserted into the soil and suck in the leachate using negative pressure. The leachate is then analyzed in the laboratory to determine how the concentration/proportion of heavy metals in the groundwater has changed over time.

The experimental set-up comprises 4 different variants, which were implemented on the three subplots:
1. an area with sward
2. an area with completely removed sward
3. an area on which the self-grown plants or grasses are used

A particular focus is on whether the specially cultivated plants are able to measurably reduce the pollution of the leachate and thus achieve an improvement for the groundwater.