HPC against paper sludge

Farmland and aquifers in Baden-Württemberg are contaminated with paper sludge. There are both causes of and solutions for this large-scale contamination.

Luck played a role: After a fire in Baden-Baden, the waterworks there checked their water source for polyfluorinated chemicals (PFC). After all, a foam which formed a film was used to fight the fire and seeped into the groundwater. Such foams contain perfluorooctane sulfonic acid, a PFC. They have been used in tanker accidents, aircraft accidents and fires in refineries. They have been banned since 2011.

The surprising thing: PFCs were by far not the only contaminant found in the plume, i.e. the resulting body of polluted water within an aquifer. Large amounts of PFCs were found, but not so many from the chemicals used in the fire-fighting foam. Instead, the analysts found high amounts of perfluorooctanoic acid. This additive is used, for example, for the non-stick coating of pizza boxes and sandwich paper or the waterproof layer of disposable coffee cups.

So many people find these PFCs quite practical in everyday life. However, they can also be toxic and, depending on the level of concentration, they can be carcinogenic, as explained by Ms Bernadette Bohnert, Head of Department for Contaminated Sites at HPC in Stuttgart.

It is problematic that PFCs can accumulate in plants, animals and ultimately in humans. Even more problematic was their high level of occurrence at the water works, their slow degradation rates and initially, their unknown origin in Baden-Baden.

Some gifts may not be what they seem

Finally, evidence was found that between 2005 and 2008, some farmers had unwittingly spread paper sludge as compost on arable land. Since 2005, the waste from paper production may no longer be disposed of in landfills. However, several million tonnes of paper sludge are produced in Germany every year. A compost company from Bühl in Baden-Baden bought more than 100,000 tonnes of such sludge, mixed it with compost and gave these mixtures to farmers.

More than 1,000 hectares of farmland in Baden-Württemberg are affected in some way by PFC contamination. Not all farmers accepted the free compost. Some of them bought, leased or exchanged contaminated soil. But it is not only the soil that is polluted: beneath the fields lies the Upper Rhine aquifer, one of the largest aquifers in Europe. And Baden’s soils are known for their water conductivity. Pollutants penetrate comparatively quickly into the groundwater with seepage water. According to estimates by the Rastatt waterworks, at least 130 million cubic metres of groundwater are affected. Today, many farmers can no longer use their own water for irrigating their fields or must purify it first.

What happens now?

“Unfortunately, the cause of such large-scale pollution can hardly be remedied,” says Bernadette Bohnert.” For areas close to the city, it’s then a case of: commercial areas instead of playgrounds, sealing surfaces and not allowing cellars, and avoiding excavation – because nobody wants that.” But the area is not only too big to be asphalted and concreted over for car parks and commercial areas. The real tragedy is that these soils are fertile farmland. The water is also still being used. “Where groundwater is extracted, the groundwater is of course purified if necessary,” Bernadette Bohnert explains. How PFC contamination in water is dealt with therefore depends on the intended use and location.

There are plants in which PFC is chemically bound and filtered out of pumped water. Meanwhile, the Baden-Baden public utility installed a low-pressure reverse osmosis system and the Rastatt waterworks activated a carbon filter.

It is not only the various technologies for contaminated site remediation and water filtration that help with the PFC challenge. Farmers also have an influence with crop rotation: experiments have shown that grain maize, for example, hardly absorbs PFCs. However, PFCs accumulate strongly in wheat and triticale. Authorities and the Baden-Württemberg Ministry of the Environment have already spent several million Euros to limit the effects of PFC contamination on the affected rural and urban districts.

Now it is time to develop and implement an efficient mix of solutions.
Bohnert and her colleagues support these diverse communities. Their interdisciplinary team unites geoscientists, chemists, biologists and engineers. They rely on pragmatic solutions to enable the continued use of the land.