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Advanced Nitrogen Treatment - Microbial Immobilization Technology

PEGASUS*1 is an advanced sewage treatment process that promotes nitrification and uses inclusive immobilization supports.

Our Key Technology

Microorganisms entrapment

Microorganism entrapment by PEG
Hitachi has already used the gel entrapment technique in many installation.

  • Reaction is faster (Tank is smaller)
  • Performance is stable



The biological reaction tank is partitioned into an anaerobic tank and an aerobic tank, and nitrifying pellets containing highly concentrated, immobilized microorganisms are added. This nitrogen treatment process promotes nitrifying reactions. This process can also be combined with physiochemical phosphorus removal methods such as biological phosphorus removal or adding coagulants to remove phosphorus.


  1. Simultaneous BOD/nitrogen treatment is possible with a residence period of 6-8 hours.
  2. Nitrogen removal efficiency is stable even at low temperatures.
  3. Nitrogen removal efficiency is stable even when combined with simultaneous coagulation methods.

(in-house comparison)

System & device summary

Anaerobic-anoxic-aerobic type PEGASUS (BOD, nitrogen, phosphorus treatment)

Photograph: PEGASUS 4

Standard PEGASUS structure

Circulation-type PEGASUS (BOD, nitrogen treatment)

Image: Standard structural diagram

Image: Standard PE structural diagram

Comparison with existing methods

The residence period is 6-8 hours, and the system is easy to apply to existing standard activated sludge-method treatment facilities.

Image: Diagram comparing PEGASUS to existing methods
Easy upgrade from existing plant

Aerobic tank

Independent support-type PEGASUS (ammoniacal nitrogen treatment)

Photograph: PEGASUS 1

Fields of application

  • Biological reaction tank


PEGASUS is a Japan-registered trade mark of Hitachi, Ltd. and Japan Sewage Works Agency.
Bio-N-Cube is a registered trademark of Hitachi Ltd. in Japan.