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  1. The A2F process is a combined enhanced aerobic filter and aerated filter.
  2. A reduction in the generation of sludge and aeration volume can be achieved. Hitachi has extensive experience and know-how with this system (46 sites in Japan as of 2016).
  3. Approximately 2/3 of organic matter in the sewage water is gasified by the anaerobic reaction, resulting in a small quantity of sludge and low power usage and operating expenditure.
  4. This process is suitable for small-scale municipal sewage water treatment (less than 10,000m3/d).


Flow diagram and Structure


  1. Low sludge production
  2. Energy saving (low aeration volume)
  3. Easy operation (no need for sludge control)
  4. Stable performance

(In-house comparison)


  • Increase of small-scale WWTP in developing countries.(Urban→Regional)
  • Necessity for low environmental impact for WWTP
  • Insufficiency of skilled operators for WWTP
  • Aerobic biological process has high OPEX
  • Conventional anaerobic process has low OPEX, but controllability is inferior.