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<International Source Book On Environmentally Sound Technologies
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7.11.4 Wastewater in Chisinau

In the capital Chisinau, about 95% of the population is connected to the sewage system. The other 5% of the population discharges its wastewater into pits, which are cleaned by special slurry-cars and discharged into the municipal sewage system. According to the data of APA-Canal, the length of the sewage system is increasing, (see table 7.19). Newly built houses have to be connected to the sewer system.

In the last decade, not only the amount of discharged municipal wastewater has diminished, but also its concentration (see table 7.18)

Table 7.18: Characteristic of discharged wastewater of the treatment plant in Chisinau (mg/l)

Parameter 1990 1995 1998
BOD5 14 6.6 5.5
Suspended matter 22 9.6 9.2
NO3 5.02 - 2.9
PO4 2.1 - 1.6

The combined sewage network discharges into the only treatment plant in Chisinau which has a capacity of 380'000m3/24 hours. Here, the wastewater is mechanically and biologically treated. However, there is no N and P removal available. The removal efficiency of the treatment station varies (after mechanical treatment) for suspended matters between 55-60% and for BOD5 between 20-25%, and is - after biological treatment - about 92%. After treatment the wastewater is discharged into the small river Bijk.

Table 7.19: Sewage network and wastewater discharge in Chisinau

  Unit 1990 1995 1998
Sewage network length km 594 677 737
Discharge capacity of the treatment plant 1000 m3/24 hours 440 445.2 445.9
Total discharge of the treatment plant* 1000 m3 135568 124684 120857.7
Note: * All wastewater discharged by the treatment plant is biologically treated.

In Chisinau, as well as in the whole country, the generation of wastewater is still declining, because of the severe economic crisis. From households, the amount of wastewater increased during the last years, whereas it went down in the public sector (administration, schools, kindergartens, etc) and in the industrial sector (table 7.20).

Table 7.20: Share of wastewater generation by sectors in Chisinau (in %)

Sector 1996 1999
Households 74.5 82.6
Public sector (administration, schools, kindergartens, etc.) 15 9.1
Industry 10.3 8.2

The decline in industrial wastewater generation has led to an increase of concentration of hazardous and other substances in industrial wastewater. This is especially true for heavy metals, substances for food conservation, colorants and surface-active synthetic substances. However, the BOD5 declined at the same time from 157.5 mg/l in 1990 to 103.7 mg/l in 1998. Furthermore, in the last years the industrial wastewater contains unknown or less known substances, which have adverse impact on the treatment process. Because of limited capacity and equipment in laboratories these substances cannot be analysed.

In the mid 1970s, methane was used for heating purposes. As the installations did not comply with air pollution and other technical standards, the project was terminated. Today, with the help of the Netherlands, two of these methane tanks will be reconstructed and will contribute to the energy supply of the treatment plant and the surrounding outskirts. The generated sludge (with 75% of humidity) is transferred to sludge fields. The fields are overloaded and the impermeability of the bottoms is no longer assured. In 1999, 64 t/per 24 hours of sludge were produced and disposed on the already overloaded sludge fields. The BOD5 of the sludge is about 150 mg/l. In order to get rid of at least some sludge, APA-canal pays already 50% of the transport costs to fields. The amount of reused sludge is minimal.

In 1999, financial resources for investment and reconstruction were jointly provided by APA-canal, the Government and the European Development Bank. Of this,50% of the money will be used for the reconstruction of the drinking water and sewage networks in Chisinau. Another project is going on with the reconstruction of the two available methane tanks in the treatment station in Chisinau. The methane will be used for heating purposes. This project is carried out with the financial support of the Netherlands.


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