Restoration of the Hoan Kiem Lake in Hanoi/Vietnam
Restoration of the Hoan Kiem Lake in Hanoi/Vietnam
Partners:
- GSan - Ökologische Gewässersanierung GmbH (GER)
- HGN Hydrogeologie GmbH (GER)
- Duc Minh (Hanoi/VN)
- Wastewater Utility Hanoi (VN)
Funding: Federal Ministry for Economic Affairs and Energy (BMBF)
Duration: 02/2005 - 02/2006
Project description:
Hoan Kiem Lake is located in the heart of Vietnam's capital, Hanoi, and is a tourist attraction with The Huc Bridge leading to a small island with the famous Jade Mountain Temple. According to legend, a sacred turtle once lived here and today a specimen of the Yangtze giant soft-shelled turtle still lives in this lake. It is believed to be one of the last 5 living individuals of this species on earth. This species of turtle, formerly common in rivers in Southeast Asia, is thus one of the most endangered species of the present day and conservationists of many countries are strongly committed to its preservation, which includes the protection of the habitat of the animal and thus the lake.
The size of the water body is about 13 ha, with a volume of about 150.000 m³ and an average water depth of 1,5 m. The deeper sedimentary layers are yellowish (lacustrine-fluviatile) sands and clays formed by transport in inland lake or river waters. The upper layers have an anthropogenic origin. Over the centuries, the resulting wastewater was discharged directly into the lake. Since the beginning of the 19th century, many dye works and tanneries settled in the north of the lake, which further polluted it.
Today, there are many smaller businesses of all kinds in the downtown area whose pollutants enter the lake. Another unresolved problem is fecal germ pollution from the use of domestic and public toilets near the lake, which are simply discharged untreated into the lake.
In the two investigations in 1997 and 1998/1999, respectively, sediments were taken from the lake and subsequently analyzed. Heavy contamination by heavy metals was found. In order to determine the actual extent of the contamination, it is planned to take aggregate samples, which will examine the entire sludge.
The envisaged method SEDITURTLE ® is a system composed of modules, which works quietly and cost-efficiently. The mode of operation of the electrically driven underwater suction unit corresponds to the lifting principle. The sediments are removed layer by layer and enclosed in pressure pipes mixed with water. They are then treated.
Work on the project will proceed in three sequential steps in close cooperation with MOST and HSDC.
1: Sample collection and analysis of sludge and water, assessment of already existing data, expansion of contacts with key Vietnamese authorities.
2: Remediation concepts for the lake will be compiled and the first experiments conducted.
3: Restoration and desludging by means of the so-called "soft-desludging", i.e. a desludging of the lake bottom that is gentle to the natural environment.
Poster about the project in English (pdf-file, 865 KB)