Stora Enso’s Kabel mill has teamed up with the local community to optimise the treatment of industrial and municipal waste water.
Located in the German city of Hagen, Kabel mill produces coated mechanical papers for Central European markets. Like any paper mill, Kabel requires large amounts of clean water as an ingredient for paper and for example to cool machinery.
The mill obtains water from the nearby River Ruhr, a tributary of the Rhine. Most of the used process water is returned back to Ruhr – a river providing drinking water for some 4.6 million people – after being purified at the mill’s waste water treatment plant.
Kabel mill treats the waste waters coming from its own production, making sure that the water from the mill is safe to return to the river. On top of this, the mill treats municipal wastewater from the homes, schools and workplaces of local communities Boele, Helfe, Kabel and Westhofen. The mill’s waste water treatment plant has the capacity of purifying 630 000 m3 waste waters annually.
A splendid blend
Combining the wastewater streams of the mill and the four municipalities with some 36 000 residents has turned out to be good way to find synergy in water purification – one stream’s challenge has become another stream’s solution.
“The water from paper production has a high level of organic compounds, which we purify in the wastewater treatment plant. At the same time it lacks some important nutrients such as nitrogen, which is necessary for the treatment process,” explains Mareike Weber, Kabel mill’s Environmental Protection Manager. “On the other hand, the municipal waste water has excessive loads of nitrogen compounds.”
The trick has been to combine the wastewater flows from the mill and the municipalities to create an optimal blend. After separate pre-treatment processes – during which solids are removed from the municipal wastewater by the non-profit water management company Ruhrverband, and process water is pre-treated in-house at Kabel mill – the two wastewater streams are blended and biologically purified at the mill. As the nitrogen surplus in the municipal waste water compensates for the nitrogen shortage in the paper mill’s wastewater, there is no need to add nutrients in the process.
For a cleaner River Ruhr
The unique collaboration has begun already in 1970, and over the years, Kabel Mill and Ruhrverband have deepened their co-operation for better waste water treatment. The local waste water quality has improved constantly, for instance through adding an anaerobic cleansing phase in the process. As new communities have joined the partnership, the purification capacity of the water treatment plant at Kabel has increased – for the best of the River Ruhr.