Sewage Sludge

Characterisation of polyelectrolytes and the preparation of special simplex structures for the dewatering of sewage sludge

The synthesis of biodegradable polymers contributes to the optimisation of sewage sludge dewatering. Sludges from drinking water treatment which are conditioned by this method are suitable either for trouble-free long-term disposal or for ecologically sound and economically viable recycling on agricultural land.


The treatment of drinking water generates substantial quantities of sludge, which must be dewatered using chemical flocculating agents prior to disposal. The limited or non-existent biodegradability of the majority of these agents leads to environmental problems where dewatered sludges are to be used as landfill or recycled on agricultural land.

For the optimisation of current sludge treatment practice, this project involved the investigation of a mechanism for the dewatering of sludge based upon the use of model polymers. Research has focused on special electrochemical methods and electrokinetic processes for the definition of the surface charge characteristics of colloidal systems.


  • Sewage sludge dewatering by the use of biodegradable polyelectrolytes has been successfully achieved. The most technologically beneficial solution has proved to be the “half-neutralisation” mechanism involving bridge formation associated with the use of long-chain linear polycations.
  • The following conclusions have been drawn with regard to the synthesis of biodegradable flocculating agents:
  • The cationic polyelectrolyte must have a mole mass in excess of 100,000 mol/l, and must show a linear molecular structure.
  • The formation of intra- or intermolecular hydrogen bridges should be prevented.
  • Findings derived from the model polyelectrolytes considered have been transferable to other polyelectrolytes, such as polyvinylalcohol-graft polymers (PVA-P-MADAM).
  • The development of specific system solutions for other types of waste water will be possible using the combination of methods described here.

More Project Informations

Project title: Sewage sludge dewatering using biodegradable polyelectrolytes as flocculating agents: characterisation of polyelectrolytes and the preparation of special simplex structures

Project number: 02WS9424/4

Project period: 1994 - 1997

Project region: Germany (Brandenburg)

Project contact:

Herr Prof. Koetz
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++ 49/3319/775220
++ 49/3319/775054

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