An expanded granular sludge bed (EGSB) reactor is a variant of the UASB concept. The distinguishing feature is that a faster rate of upward-flow velocity is designed for the wastewater passing through the sludge bed. The increased flux permits partial expansion (fluidisation) of the granular sludge bed, improving wastewater-sludge contact as well as enhancing segregation of small inactive suspended particle from the sludge bed. The increased flow velocity is either accomplished by utilizing tall reactors, or by incorporating an effluent recycle (or both). A scheme depicting the EGSB design concept is shown in this EGSB diagram.

The EGSB design is appropriate for low strength soluble wastewaters (less than 1 to 2 g soluble COD

Chemical oxygen demand

In environmental chemistry, the chemical oxygen demand test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water or wastewater, making COD a useful measure of water quality...

/l) or for wastewaters that contain inert or poorly biodegradable suspended particles which should not be allowed to accumulate in the sludge bed.

See also

• Anaerobic digestion
  Anaerobic digestion
  Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen. It is used for industrial or domestic purposes to manage waste and/or to release energy....
  
  
• Anaerobic digester types
  Anaerobic digester types
  The following is a partial list of different types of anaerobic digesters. These processes and systems harness anaerobic digestion for purposes such as sewage treatment and biogas generation.Examples include:*Anaerobic activated sludge process...
  
  
• Upflow anaerobic sludge blanket digestion
  Upflow anaerobic sludge blanket digestion
  Upflow anaerobic sludge blanket technology, normally referred to as UASB reactor, is a form of anaerobic digester that is used in the treatment of wastewater....