Biological Effluent Treatment

Development of ecologically sound separation processes for the production of high-value textile fibres in Germany

The technical solutions developed and the tests carried out to improve the environmental sustainability of the water retting process prove that fibres of high and consistent quality can be produced from the raw materials hemp and flax. At the same time, this resulted in cost advantages over the field retting practised to date in Germany.



In the traditional production of bast fibres, the biological fibre separation is carried out by means of field or water retting, which exposes the fibre bundles and places them in a condition in which they can be processed. Environmentally sustainable methods must be developed so that water retting can be carried out in accordance with the environmental standards in force in Germany. Otherwise the use of domestic hemp and flax fibres will only remain possible to a limited extent.

The overall aim of the collaborative project was therefore in the development of procedures for: 

  • the preparation and additional processing of bast fibres; 
  • environmentally friendly water retting processes; 
  • the cleaning and re-use of the liquid effluents arising from the retting process; 
  • the elimination of odour problems arising from the retting processes; and 
  • the recovery of energy. 


  • For the cleaning of liquid effluents from the retting of flax and hemp, the following techniques were tested on a pilot scale: 
  • Modified aerobic sequencing batch reactor (SBR) process by means of a mixed-loop reactor, modified fixed-bed biology and anaerobic biology in combination with a fixed-bed biology. The results are promising. 
  • The water retting tests with recycled water corresponded with those with fresh water. 
  • A bio-filter was successfully tested in connection with the elimination of odour-intensive pollutants in the exhaust air from the water retting. 
  • The burning of the shives and hurds arising from the manufacturing process in the boiler plants of the retting works lends itself to a reduction in the energy used by the fibre separation process. 
  • When considering profitability, water retting exhibits a cost advantage over field retting, based among other things on improved fibre properties.

Project Participants

Implementing Institution

EnviroChemie GmbH

Cooperation partner

German Institutes for Textile and Fiber Research (DITF)

More Project Information

Project title:  Development of ecologically sound separation processes for the production of high-value textile fibres in Germany (Part 1)

Project number:  0339886

Project period:  2000 - 2003

Project region:  Germany (Baden-Württemberg)

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Source: German National Library of Science and Technology Hannover (TIB)