Successful partical commissioning of the ara bern major project

Hardly any other raw material is as important as water. This is why the careful treatment of waste water is so important. One of the largest waste water treatment plants in the whole of Switzerland is the ara region bern ag. In addition to the purification of waste water, biowaste is also treated there. Furthermore, bio-methane for the public gas networks is produced from the organic components. The ara bern waste water treatment plant was expanded this year, to include a new receiving and processing plant for commercial bio-waste. The project is one of the largest ever for Tietjen and is being implemented together with a partner from the dosing and washing machine technology sector.

The first milestones had already been reached in July 2019 - by this time, most of the plant components had been delivered and the customer's new building shell had been completed. We are proud that the partial commissioning of the processing plant took place at the end of April this year.

Hand in hand for success
Together with our partner in the field of dosing and washing machine technology, we were able to deliver one of the best processing plants for commercial biowaste, with the Tietjen Double Rotor Separation Mill (DRM 800) in the centre. In addition, our employees took over the project management, planning and organization on site. Thanks to this cooperation, all the parts for one of the most modern processing plants for food waste could be supplied from one source and individually adapted to the customer's needs.

Functionality of the processing plant
The bio-waste, which comes from supermarkets, restaurants and canteen kitchens, is delivered by lorries as well as various waste containers. The reception area, with a large bunker, provides space for unloading trucks and contains a fully automatic system for emptying, cleaning and storing the containers. From the bunker, the homogenized bio-waste is transported to the heart of the plant - the Tietjen DRM 800.

Simple separation and processing of food and packaging
Before fermentation, it is essential to separate bio-waste from foreign matter and impurities. The more thorough and better the separation is from the beginning, the more economical is the entire process.
In contrast to conventional process technologies, the DRM 800 enables the precise separation of organic materials from all foreign matter, such as plastic packaging, right at the beginning of material processing. The shredded and mixed organic material can then be optimally recycled in terms of energy and material, while the foreign substances can be fed into thermal recycling according to type. With the lowest energy and wear and tear costs, the DRM separates foreign matter and shreds the organic material to less than 12 mm in one operation, in accordance with the legal requirements.

Within the scope of this major project, Tietjen also installed two large storage tanks with a volume of 150 m³ each, to buffer the purely organic material for a constant supply for fermentation. To prevent sediments from entering the fermenter, an additional sedimentation tank was also installed by our partner. In combination with a tubular heat exchanger, the organic material thus enters the fermenter under optimal conditions. The project also included the complete pipeline construction as well as the specification of the overall process.
The overall commissioning should be completed shortly.

For further information on this project, please contact Lars Weiß at or Frank Lippert at

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