Population equivalent

Industrial water treatment

Regeneration of the Llobregat River Delta and of the coastline near the river mouth, thus improving the bathing waters of the beaches located between Barcelona and the Garraf Massif.

It is one of the largest purification plants in Europe, combining two large processes that operate in parallel: water line and sludge line.

General Information

  • Project: Wastewater treatment plant, Baix Llobregat.
  • Entity: Sociedad Depuradora del Baix Llobregat, S.A.
  • Location: Prat de Llobregat, Barcelona (Catalonia). Spain.
  • Capacity: 420,000 m3/d
  • Equivalent population: 2,275,000 people

Key points

Water line:

  • Prefilter wells with screens with grids with 100 mm of separation between bars and 2 bivalve grabs with 500 litre capacity.
  • Raw water pumping with 8+1 centrifugal pumps with the capacity to elevate up to 6,526 m3/h each and with trim.
  • Discharge of thick and thin solids, in 8 channels equipped in 2 lines. Elimination of sand and oils using 12 desanders-deoilers.
  • Measurement of the flow and by-pass to limit the flow entering the biological treatment to 35,000 m3/h.
  • Twelve 20x60 m rectangular primary decanters.
  • Biological treatment in 8 lines through activated sludge, combining anaerobic, anoxic and oxygenation processes.
  • 14 circular secondary decanters with a diameter of 45.5 m.

Sludge line:

  • Sifting and thickening of sludge using 4 thickeners.
  • Thickening of excess biological sludge using 4 centrifuges of 260 m3/h.
  • Anaerobic sludge digestion using 8 digesters, each 7,180 m3.
  • Four centrifuges, each 60 m3/h for the dehydration of digested sludge.
  • Low storage of gas in 2 membrane tanks.
  • Thermal drying of dehydrated sludge.
  • Energy recovery from the digestion gas using 4 motor generators, each 2.8 MWe.
  • Odour treatment for pre-treatment deodorising.

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