Biological processes

Biological purification is based on the natural metabolism of microorganisms and uses this to convert unwanted water ingredients into other products (e.g. carbon dioxide, water). The biological processes can take place in the presence of oxygen (aerobic) or without atmospheric oxygen (anaerobic). As a rule, therefore, hardly any use of chemicals or energy is required for biological cleaning.
In practice, there are very different plants in which microbiological processes play an important role (among others):
- Open activated sludge tanks in municipal sewage treatment plants for COD degradation (sedimentation of the activated sludge / biomass takes place in the secondary settling tank, whereby a partial stream is recycled to keep the concentration of microorganisms in the activated sludge tank sufficiently high)
- Fixed-bed reactors or fluidized-bed reactors with packed bodies as growth surface for a biofilm for pollutant elimination (excess biomass is flushed out by means of flushing)
- Filter containers with filter sand as a growth area for microorganisms for demanganization (excess biomass or manganese sludge is rinsed out by means of flushing)
  • Nitrification
  • Demanganization
  • Degradation of pollutants
  • COD removal