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Sewage Sludge Drying

The products of waste water treatment plants are the purified effluent and the solids, known as sewage sludge or biosolids. While the clean water can be disposed to a river or even be reused after further treatment, the final disposal or use of the solids needs some additional efforts. Depending on the sludge quality and the local situation the sludge can be finally disposed to landfill, used as a fertilizer and soil conditioner or used as an energy source. In the near future phosphates will be recovered from the sludge.

The usage of the sludge as a well defined product becomes more and more prominent. Prior to full drying are the treatment steps needed for transforming the sludge to a valuable product. SMS offers sludge drying systems for treatment of sludge from municipal as well as from industrial waste water treatment plants. Variations of this sludge treatment process are:

Pre-drying up to

  • 35 to 50 % dry solid content before incineration in fluidized bed incinerators
  • 65 to 75 % dry solid content before combined incineration with garbage, composting or landfill

Full drying up to 85 to 95 %

  • before thermal utilization as bio-fuel for cement kilns, coal fired power stations, pyrolysis, gasification or other conversion processes
  • before composting and agricultural usage as fertilizer and for soil reclamation

In all these drying processes the thin film dryer is the first choice.

SMS sludge drying process

The core of the installation is the horizontal thin film dryer. Depending on the application the evaporation capacity per dryer is up to 8 tons of water per hour.

The unique benefits of the SMS sludge drying system are:

  • 1-stage operation passing the sticky or pasty phase
  • no back mixing of dried product
  • minimum amount of off-gas
  • self-inerting by evaporated water

All these advantages make the thin film sludge dryers very successful. More than 100 machines are installed worldwide.

Principle flow sheet of 1-stage sludge drying system
Sludge dryer with vapour condensation system