Ventilation fans

Biological treatment buildings

Active sludge

Biological treatment

Water from primary sedimentation undergoes biological treatment in eight tanks supplied with pure oxygen. Micro organisms growing in these tanks remove the residual organic matter present in the water after the primary sedimentation. They transform it with oxygen into carbon dioxide (CO₂), water and new biomass, which represents the growth of the micro-organisms. The collection of micro organisms and inorganic precipitates together are mentioned activated or secondary sludge.