General Cleanup Technology

Water Treatment and Sediment Remediation at the Hoan Kiem Lake, Hanoi

The joint project developed technologies for the in situ treatment of water and sediments of the Hoan Kiem lake in Hanoi. The employed bioreactors can remove ammonium from the filtrate water of dewatered sediments. In situ sediment remediation can reduce the formation of hydrogen sulphide and redissolution of phosphorus in heavily contaminated urban water bodies


The objective of the present sub project was to develop methods for the in situ treatment of sediments and water of the Hoan Kiem lake in Hanoi. Filtrate water from dewatered sediments was treated with a bioreactor to remove ammonium. The water from the reactor, enriched with oxygen and nitrate, was then brought into contact with water layers close to the sediment. Experiments were initially conducted with a floating test reactor in a fish pond. Filtrate water treatment of the Hoan Kiem lake, however, was undertaken with an external biofilter since areas close to the shore were too shallow for a floating reactor. Parallel to this, three different bioreactors were conceptualized, constructed and tested in Thailand. All reactors are based on the principle of a filter with biofilm aerated from below, through which the water flows from top to bottom. The throughput of all reactors is between 0.5 - 1m3/h. Methods for sediment remediation were examined using long term laboratory experiments.


  • Nitrification rates of up to 0.25g NH4-N/(m2*d) were achieved with the Vietnamese test reactor (specific surface area: 500m2/m3, support material: Cleartec® Biotextil), i.e. 0.25g of ammonium were converted to organic nitrogen on every square metre of filter surface per day.
  • The test reactor mixes oxygen with the water (oxygen saturation: 100%).
  • The Thai reactors (specific surface area: 100 m2/m3, support material: 2H PP-Media NET 150) achieve a nitrification rate of up to 0.8 NH4-N/(m2*d) and BOD5 removal of 4g/(m2*d). The treated water enriched with oxygen and nitrate improves redox conditions for the sediment interstitial water, e.g. by preventing the biogenic formation of hydrogen sulphide.
  • The use of the remediation agent calcium nitrate in combination with metal salts is able to degrade nitrate to >70% within six weeks by application of 150g NO3 – N/m2.
  • An oxic environment can be maintained in the sediment, reducing the redissolution of phosphorus and heavy metals.
  • Polyaluminium chloride achieves the best results for removing turbidity by in situ flocculation, i.e.  a reduction from 30-60 NTU to 3-10 NTU.

Project Participants

Implementing Institution

Ingenieurbüro Dr. Frank Panning

Technische Universität Dresden - Institut für Abfallwirtschaft und Altlasten

Cooperation partner

University of Kalyani, International Centre of Ecological Engineering (ICEE)

Thailand Institute of Science and Technological Research (TISTR)

Hanoi University of Mining and Geology

Vietnamese Academy of Science and Technology (VAST), Institute of Environmental Technology (IET)

Hanoi University of Science, Chemische Fakultät

Hanoi People’s Committee


Herbst Umwelttechnik GmbH

GSan Ökologische Gewässersanierung GmbH (GSan)


Promoting institutions

Federal Ministry of Education and Research (BMBF)

More Project Informations

Project title:  Entwicklung von Strategien und Verfahren für eine nachhaltige Sanierung, Stabilisierung und Bewirtschaftung des Hoan Kiem Sees in Hanoi, Vietnam / Teilprojekt Anpassung und Weiterentwicklung von insitu-Verfahren zur Sediment- und Wasserbehandlung

Project number:  02WT0931

Project period:  2008 - 2010

Project region:  Germany (), Vietnam

Project contact:

Herr Prof. Dr. rer. nat. Dr. h.c. Werner

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