There are two basic principles:

  1. Biological treatment and
  2. Chemical treatment

The two categories are often combined.

Primary treatment, removal of particles:

  1. Screen
  2. Sand and Grit removal
  3. Pre sedimentation

Biological treatment (secondary treatment)

  1. Biofilm processes (MBBR, MBR).
  2. Activated sludge processes (oxidation ditch, SBR).
  3. Activated sludge processes for removal of Nitrogen and Phosphorus.

Typical processes combinations are illustrated as: