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Phosphorus recovery from sludge and ashes

Sustainable sludge handling

The projects is aimed on recovery of phosporus from sludge from wastewater treatment plants.
Phosphorus recovery from sewage sludge has been studied in experimental works by leaching SCWO, Super Critical Water Oxidation, residues, sludge incineration ash and co-incineration of sludge and municipal waste with acid and base.

Participating persons:

Project leader

Erik Levlin, PhD

Scientist

Bengt Hultman, Professor

Doctors student

Kristina Stark, Tekn. dr.

External cooperation partner

Agnes Mossakowska, Stockholm Water Company.

Laboratory

Monica Löwén, research engineer

Land and Water Chemical laboratory has been used for leaching work and analysis of phosphorus content in leachates.

VA-Forsk

VA-Forsk have 2003 given grants for studying phosphorus recovery by leaching ash from incineration and sludge residue from supercritical water oxidation with acid and base. Leaching with base gave a small contamination of metals in the phosphorus product and acid leaching gave a high phosphorus recovery. The work have been reported in VA-Forsk 2004-03.

Year 2004 grants have been given for further experiments. A two step method for phosphorus recovery has ben studied, which combins the high phosphorus recovery of the acid leaching with the small contamination of metals of the leaching with base. In a first step the sludge is leached with acid at pH 4. Therefter leaching in a second step be made with base. The recovery at leaching with base is increased when calcium which binds phosphorus at alkaline conditions, first is leached at pH 4. Two step leaching gave more leaching of phosphate, however, not as high as for leaching with acid.

The high per cent of leached phosphorus compared to leached metals at leaching with acid and the lower cost for acid (90 Euro/ton for HCl ) than for base (265 Euro/ton för NaOH) makes leaching with acid less expensive than leaching with base. If only metal phosphate is leached the dissolved amount of metal will be 3 equivalents per mole P. Cost for acid leaching with HCl is about 0.32 Euro/kg P (3 mole HCl per mole P) and upwards depending on the amount of dissolved metals. Leaching Mora sludge incineration ash with 1 M HCl dissolves about 3.49 equivalent metal ions per mole phosphate, which gives a cost of 0.37 Euro/kg P. Cost for base leaching with NaOH is about 1 Euro/kg P (3 mole NaOH per mole P). The cost for chemicals for two-step leaching is estimated to 1.2 Euro/kg P and upwards. The work have been reported in VA-Forsk 2005-12 and at IWA Specialized Conference - Sustainable sludge management 29-31 May 2006 in Moscow Russia.

MISTRA

Mistra finance 1999 to 2005 a PHD student within the Mistra programme Sustainable Urban Water Management.

Doctors thesis:
Stark K. (2005) Phosphorus release and recovery from treated sludge. Dep. Land and Water Resources Engineering, KTH, ISBN 91-7178-123-4.

Licenciate thesis:
Stark K. (2002) Phosphorus release from sewage sludge by use of acids and bases. Dep. Land and Water Resources Engineering, KTH, ISBN 91-7283-307-6.

Stockholm Water Company

Stockholm Water has until 2002 contributed to finansing the project.

Internationell presentations:

Poster at 1st World Water Congress in Paris, 3 - 6 July 2000: Levlin, E., Löwén, M., Schmidt, E., Hultman, B. and Mossakowska, A. Phosphorus recovery from sewage sludge incineration ash.

OH at 2nd World Water Congress in Berlin 15-18 October 2001: Levlin, E., Löwén, M., Stark, K. and Hultman, B. Effects of phosphorus recovery requirements on Swedish sludge management.
The articel has also been published in Water Science and Technology Vol 46, No. 4-5, pp. 435–440. 2002.

Two posters at 3:d World Water Congress in Melbourne 7-12 April 2002:

  • Poster: Stark, K., Hultman, B., Levlin, E., Löwén, M. and Mossakowska, A. Calculation of chemical needs in combined phosphorus removal and recovery at Henriksdal WWTP, Sweden.
  • Poster: Stark, K., Hultman, B. and Levlin, E. New system technology for combined phosphorus removal and recovery.

Presentation at 2nd international Conference on Recovery of phosphates from sewage and animal wastes, Noordwijkerhout Netherlands 12 - 13 mars, 2001 Hultman, B., Levlin, E., Mossakowska, A. and Stark, K. Effects of wastewater treatment technology on phosphorus recovery from sludges and ashes.

Reports from Stockholm Water Company:

  • Hultman, B. Levlin, E., Löwén M. and Mossakowska, M. Uthållig Slamhantering. Förstudie. Stockholm Vatten AB, R. Nr 23 sept-97, 1997
  • Levlin, E., Löwén, M., Schmidt, E., Hultman, B. and Mossakowska, A. Fosforutvinning ur aska. Stockholm Vatten AB, R. Nr 54 nov-98, 1998.
  • Hultman, B., Levlin, E., Löwén, M., Mossakowska, A. and Stark, K. Utvinning av fosfor och andra produkter ur slam och aska, delrapport, Stockholm Vatten AB, R. Nr 6 mars 2001.
  • Hultman, B., Levlin, E., Löwén, M., Mossakowska, A. and Stark, K. Utvinning av fosfor och andra produkter ur slam och aska, Slutrapport. Stockholm Vatten AB, R nr 02, feb 2002.

Swedish - Polish Research Co-operation

Papers about phosphorus recovery have been published in reports from seminars of the Swedish - Polish Research Co-operation:

Levlin E. Sustainable sludge handling - Metal removal and phosphorus recovery, Report No. 3, Advanced Wastewater reatment Nowy Targ, October 1-2, 1998.

Levlin E. Resources recovery from incineration ashes, Report No. 5, Sustainable municipal sludge and solid waste handling, Stockholm August 24, 1999.

Hultman B. and Löwén M. Combined phosphorus removal and recovery and
Stark K. Phosphorus release from sewage sludge by use of acids and bases, Report No. 9, Wastewater, Sludge and Solid Waste Management, Nowy Targ - Zakopane, October 24-26, 2001.

Hultman, B. Levlin, E. Plaza E.and Stark K. Phosphorus recovery from sludge in Sweden - possibilities to meet proposed goals in an efficient, sustainable and economical way and
Levlin E. and Hultman B. Phosphorus recovery from phosphate rich side-streams in wastewater treatment plants, Report No. 10, Integration and optimisation of urban sanitation systems, Gdansk, 23-25 March 2003.

Levlin E., Löwén M. and Stark K. Phosphorus recovery from sludge incineration ash and Supercritical Water Oxidation residues with use of acids and bases, Report No. 11, Integration and optimisation of urban sanitation systems, Wisla October 25-28, 2003.

Levlin E. and Hultman B. Phosphorus recovery from sewage sludge - Ideas for further studies to improve leaching Report No 12. Integration and optimisation of urban sanitation systems, Stockholm June 5-9, 2004.

Levlin E. Phosphorus recovery from sewage sludge - Two-step leaching process with acid and base, Report No 13, Krakow Mars 17-19, 2005.

Publication list


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