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10808
Increased nitrogen removals
statistikk
2001-08-09T10:00:00.000Z
Nature and the environment;Nature and the environment
en
avlut, Municipal wastewater, sewer system, treatment plant, sludge, grey water, black water, sewage, discharges to water, nitrogen emissions, phosphorus emissions, heavy metals, organic pollutants, organic material (COF and BOF5), waste feesWater and waste water , Pollution and climate, Nature and the environment
false

Municipal wastewater, 2000

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Increased nitrogen removals

The wastewater treatment efficiency for nitrogen removals has increased from 24 per cent in 1999 to 28 per cent in 2000, according to figures reported by the municipalities for the year 2000. Treatment efficiency is highest in the North Sea counties (34 per cent), but the largest increase in 2000 was experienced outside this area.

Changes in treatment efficiency for phosphorus and nitrogen in the North Sea counties (Counties 1-10). 1993-2000. Per cent

Discharges of phosphorus and nitrogen per capita. County. 2000. Kiloes

Highest removals of nitrogen in the Oslo region

53 per cent of the nitrogen was removed from the wastewater by the treatment plants in the Oslo region (Oslo and Akershus counties). In 1999 this figure was 44 per cent. It is expected that this efficiency rate will increase further by next year when another large treatment plant in Oslo will remove nitrogen more efficiently. In average every resident in Oslo discharged 1.8 kilo of nitrogen in 2000, while an average resident outside the North Sea counties discharged 4.2 kilos.

Minor decrease in phosphorus removals in the North Sea counties

The treatment efficiency for phosphorus in the North Sea counties decreased by 2.2 per cent from 1999 to 2000, but the overall treatment efficiency was still above 90 per cent. For the time being it its difficult to say if the decrease is due to abnormal situations in one or several of the treatment plants, or a result of errors in the figures reported. Outside the North Sea counties the treatment efficiency for phosphorus increased from 28 per cent in 1999 to 36.6 per cent in 2000. In average every inhabitant in the North Sea counties discharged 0.11 kilo phosphorus in 2000, while every resident in the other counties discharged 0.45 kilo.

Less heavy metal in the sewage sludge

The reported figures for 2000 show a decrease in the average contents of most heavy metal in sewage sludge. There are indications of a downwards trend with regards to discharge of copper, mercury and lead. The contents of other heavy metals have shown more year-to-year variations.

Total production and disposal of sewage sludge. The whole country. 1993-1997. Tonnes dry weight

Disposal of the sewage sludge

A total of 102 000 tonnes of sewage sludge was disposed of the different purposes in 2000. This is a slight decrease from 1999, which can be explained by yearly variations in storage. 57 per cent of the sludge was used as fertilizer in agriculture, 11 per cent in parks and green spaces, 15 per cent as cover on landfills and 16 per cent for other purposes

Total discharges and treatment efficiency for different
types of wastewater treatment plants. 2000
  Total discharges Average treatment efficiency1
  Phosphorus Nitrogen Phosphorus Nitrogen
  Tonnes Per cent
Total 1 175,8 16 504,5 66,8 27,7
Direct disharges 197,8 1 478,0 0,3 0,2
Mechanical 481,6 3 823,8 30,3 24,9
Chemical 86,7 4 921,3 89,5 19,7
Biological 9,7 126,2 62,4 35,8
Chemical/biological 45,1 2 685,8 93,8 47,9
Other treatment 4,6 156,2 81,4 20,5
Separate treatment 350,4 3 313,1 32,8 15,3
1  Seperate treatment is not included.
Content of heavy metals in sewage sludge. 2000. Milligrams per kilo dry weight
  Average content Maximum registered content Limit value for agricultural areas Limit value for parks etc. Total amount in disposed of sewage sludge Change in average content 1999-2000
  Milligrams per kilo dry weight Kg Per cent
Cadmium (CD) 1,0 19,0 2 5 105 7,0
Chromium (CR) 24,8 2 190,0 100 150 2 535 -16,6
Copper (CU) 244,1 2 790,0 650 1 000 24 906 -1,7
Mercury (HG) 0,9 23,7 3 5 94 -2,7
Nickel (NI) 14,5 299,0 50 80 1 481 5,5
Lead (PB) 20,6 224,0 80 200 2 099 -14,9
Zinc (ZN) 317,4 2 708,0 800 1 500 32 390 -12,1

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