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Different water treatments produce a series of wastes that can be solid (which are incinerated or brought to landfills) or sludge, which can have a liquid or semi-solid consistency.

The composition of the sludge depends on the nature of the initial water contamination, the treatment to which the water has been subjected, and its hydrophilic colloidal matter content.

Sludge management aims to reduce sludge volume in order to minimize operating costs.

Types of sludge treatment:

  • Mechanical dewatering:
    • Filter press
    • Centrifugation
    • Dewatering screw press
    • Filter cloths
    • Thickening
  • Thermal dewatering:
    • Low temperature
    • High temperature

Prior characterization of the sludge is essential to in order to determine what type of treatment should be developed.


For the treatment of sludge originating from:

  • Primary and secondary wastewater treatment
  • Drinking water treatment plants (DWTP)
  • Treatment of mechanically dewatered sludge


  • Reduction of environmental impact by minimizing waste production and reusing waste to obtain biogas
  • Reduction of operating costs


Sludge treatment involves 4 distinct stages:

  • Thickening: mechanism by which the volume occupied by the sludge is reduced.
    This can occur using gravity, flotation, and dewatering.
  • Stabilization: sludge contains a series of microorganisms that cause fermentation.
    To avoid fermentation and the problems it generates, the sludge must be stabilized.
    Depending on the origin and organic matter content of the sludge, this can be done using chemicals or through aerobic or anaerobic digestion, on a case-by-case basis.
  • Conditioning with the objective of eliminating moisture from the sludge, in which chemical treatments are usually applied.
  • Dewatering, an operation by which most of the sludge’s water content is separated.
    There are several dewatering systems that all share one thing in common, which is that the separated water must be reintroduced into the purification system.
  • Thermal dewatering: In cases where a large amount of sludge is generated even after mechanical dewatering, thermal treatments can be considered to reduce sludge, thus lowering operating costs associated with management and environmental impact.