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DePrex® Degassing Technology

according to the DiMeR-Process

The DiMeR-process is a licensed product from DiMeR GmbH

The Challenge

Recovery of dissolved methane in anaerobically treated wastewater and sludge

Anaerobically treated wastewater contains dissolved digester gas. The methane it contains remains unused as an energy carrier and is released into the atmosphere as a harmful greenhouse gas. 

The DiMeR-process was developed in cooperation with Leibniz Universität Hannover, to efficiently remove gases from the water phase, to utilise them energetically and to make them harmless.

CNP's Solution

DePrex® degassing technology according to the DiMeR process

Operating principle

  • Suction of the digested sludge from the riser pipe by negative pressure
  • Automatic discharge of the digested sludge into a sludge chamber
  • Release of dissolved digester gas through reduction of solubilities
  • Additional acceleration of outgassing processes through fine bubble stripping (recirculation of captured digester gas)
  • Falling film enables release of residual gas bubbles into sludge matrix
  • Feeding of the captured gas on the pressure side of the vacuum pump into the existing digester gas collection line of the digesters
  • Dosing of precipitant and/or defoaming agent as required


Reduction of greenhouse gas emissions

  • Effective recovery of still dissolved methane at the outlet from the digester (overflow into sludge pocket) and return to the gas line
  • Methane recovery approx. 90% depending on pressure conditions
  • Significant reduction of greenhouse gas emissions in the sludge stack tank and during digested sludge dewatering
    (only approx. 10-15% of the originally dissolved CH4)
  • Higher overall efficiency, as installed directly at the digestion tower


DePrex® Degassing Technology

  • No additional pumps required for sludge transport
  • No installations in the reactor head that are susceptible to clogging
  • Short pipe runs for the gas line
  • Less space required as similar processes
  • No additional Ex-protection zone required
    DePrex is installed in an existing Ex-zone
  • Significantly increased overall reduction in greenhouse gas emissions from the treatment plant