Sewage Sludge

Development of a process to influence nutrient content in the further treatment of stabilised sewage sludge

Using an aerobic-anoxic secondary treatment process, it has been possible to reduce the proportion of nitrogen in sewage sludge and in process water from waste water treatment by 60% and 85% respectively. At the same time, it has been possible to reduce the dry weight of sewage sludge by up to 50%. 

 

Summary

With effect from 2005, the disposal of sewage sludge in landfill sites will be prohibited by law throughout the Federal Republic of Germany.  At the same time, the recovery of sewage sludge for use in agriculture and landscaping will assume increased significance.  This option for recovery is both ecologically sound and cost-effective, but is restricted by the contaminant and nutrient content of sewage sludge, particularly nitrogen compounds.

This was the background to the development and semi-industrial testing of an aerobic-anoxic process for the secondary treatment of sewage sludge.  This method is intended to allow the increase of ecologically justifiable volumes of sewage sludge spread on fields, thereby enhancing potential for the recovery of usable materials.

Results:

  • Nitrogen loads can be reduced by 60%.  After dehydration, the residual nitrogen content of sewage sludge after aerobic-anoxic treatment is 45% lower than that of digested sewage sludge.
  • The concentration of nitrogen compounds in process water from waste water treatment has been reduced by 85%.
  • In comparison to untreated sludge, the dry weight of sewage sludge has been reduced by 45 – 50% overall.  Aerobic-anoxic treatment therefore produces an additional reduction of 20 – 25% over conventional reduction by digestion processes.
  • The use of a static secondary concentrator has significantly improved the dehydration of sludge.

More Project Informations

Project title:  Development of a process to influence nutrient content in the further treatment of stabilised sewage sludge

Project number:  02WS9890/2

Project period:  1998 - 2001

Project region:  Germany (Thuringia)

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