Challenge

Hans Henning Junk, owner-manager of  Köhler Pappen, describes papermaking as an extremely water- and energy-hungry process: “We disperse a small quantity of fibers in a lot of water. A lot of energy is needed to treat the fibers and give them the right characteristics. And then we need even more energy to get the water out of the mat of fibers again.” And the large amounts of wastewater meant high disposal fees. To minimize wastewater volumes, the company commissioned Siemens Pulp&Paper with the installation of a treatment plant that would allow the recycling of the wastewater into the production process.

Solution

The new treatment plant is a showcase of innovation and sustainability. In a two-year project, Siemens Pulp&Paper installed a membrane bioreactor and a reverse osmosis system. In municipal water treatment, these technologies are already widely used. In the paper industry, in contrast, this type of water treatment plant is still a novelty because the specific properties of paper wastewater place special demands on the treatment process.
 
Typical for the wastewater of the Gengenbach cardboard factory is its fluctuating and usually very high lime content, which was a special challenge for the operation of the membrane bioreactor. To solve this problem, a decalcification process was added after pre-sedimentation and sedimentation. In the high-rate clarifier, lime hydrate and sodium
carbonate are added to precipitate part of the dissolved lime. For the ensuing adjustment of the pH value, hydrochloric acid is used. After a cooling phase, the wastewater is fed into the membrane bioreactor for biological clarification. With secondary-flow reverse osmosis as final step the treatment produces a solids-free, desalinated permeate fit to be
recycled into the production process.

Results

Today, the amount of wastewater to be fed into the municipal treatment plant has been reduced from 30m³ to a mere 3m³ per hour, a 90% reduction! As the recycled production water has a temperature of about 30°C, less process steam is needed, cutting the company’s annual carbon emissions by 800 tons. All this makes the project a prime example of resource conservation, earning it the support of the German Federal Environment Agency.

As an innovative cooperative project of Siemens Pulp&Paper and Siemens Water Technologies, the system installed in Gengenbach embodies the Siemens One concept of cross-industry know-how bundling to the benefit of the customer.

Download Full Case Study