Sewage Sludge Treatment

Elimination of chlorinated compounds from sewage sludges by anaerobic treatment

In sewage sludge treatment, the addition of dechlorinating bacteria from suitable sediments leads to separation of chlorineatoms and better availability for further microbial decomposition. Through this, potential pollutant entry into agricultural areas can be prevented in sewage sludge recycling.



Because of legal regulations, deposition of sewage sludge will only be allowed in the form of combustion residues from the year 2005 in Germany. For this reason, their increased use in recultivation and utilization in agricultural areas is being strived for.

Before this recycling option can be used, the danger of increased pollution through highly chlorinated compounds like polytchlorinated biphenylene (PCB) and dioxine (TCDD) must be ruled out. For this reason, tests were carried out under laboratory conditions whether reductive dechlorination through anaerobic bacteria can contribute to the elimination of chlorinated pollutants in sewage sludge. 


In the sewage sludge itself, the content of reductive dechlorinating bacteria was low. Therefore, the success of the dechlorination depends on the choice of suitable sediment material (here: Sediment from the river Saale as a natural habitat for dechlorinated bacteria). Hereby, it was possible to separate chlorineatoms, which in turn led to better availability for further microbial decomposition.

  • Dechlorinating bacteria cannot multiply in TCDD/F polluted sewage sludge without the addition of sediment.
  • The reductive dechlorination of dioxins was tested with 1,2,3,4 tetrachloro-dibenzo-p-dioxine. The dechlorination path via 1,2,4-trichlor- to 1,3- Monochloridbenzo-p-dioxin was clarified.

Project Participants

Implementing Institution

Martin-Luther-Universität Halle

More Project Informations

Project title:  Elimination of chlorinated compounds from sewage sludges by anaerobic treatment

Project number:  1460638Q/6

Project period:  1993 - 1996

Project region:  Germany (Saxony-Anhalt)

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