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The Wastewater Treatment Process

The treatment of wastewater can roughly speaking be divided into three areas: mechanical, biological and chemical treatment.

Mechanical treatment

Within the mechanical treatment all materials that should have been placed in the garbage can are removed.
At Gryaab the following mechanical processes take place:
  • Coarse separating (rubbish and paper).
  • Grit chamber that separates sand
    and gravel.
  • Preliminary settling basin where particles heavier than water are removed.

Chemical treatment

Chemicals are most of all used to remove the nutrient phosphorus. At Gryaab the following chemical processes take place:
  • In the regular treatment iron sulphate is added to precipitate the phosphate which then attach to the biological sludge and at the end are separated through settling. The sludge is later used to produce biogas equivalent to 60 gigawatt hours.
  • During flooding not all wastewater can pass the ordinary biological and chemical treatments. The extra water is collected in several preliminary settling basins where the phosphate is removed through adding polyaluminium chloride (PAC) to the water.

Biological treatment

Bacteria are used to break down the remaining organic materials. At Gryaab bacteria are used in the following processes:
  • The remaining organic material is broken down by bacteria in so called activated sludge basins and is later removed through sedimentation.
  • At the end, the bacteria help to convert the nitrogen into nitrogen gas, which is released into the atmosphere. After approximately 12 hours the wastewater has been treated and is released back into the Göta Älv river.

The wastewater treatment process is also presented in the pdf-file below.
pdf The wastewater treatment process
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Klicka för utskriftsvänlig sidaUtskriftsversion (Öppnas i nytt fönster)

visste du att?
Did You know that Gryaab runs one of the largest treatment plants in all of Scandinavia?  
Gryaab AB - Norra Fågelrovägen 3, S - 418 34 GÖTEBORG, Tel växel 031-64 74 00, info@gryaab.se