In CAS – Conventional Activated Sludge Plants, the biomass is kept in suspension and mixed with the wastewater to be treated. The stages of treatment develop in spatial sequence in several tanks.
These plants require a series of internal recirculation to facilitate the nitrogen’s removal (phases of Nitrification – Denitrification), and to reuse part of the biomass separated in the settling tank during the biological process.
The tanks sequence:
- Homogenization, to guarantee a flow rate and a constant polluting load entering the biological process;
- Denitrification, in anoxic conditions, for remove nitrogen in the form of nitrites and nitrates;
- Oxidation, under aerobic conditions, for remove the polluting organic substance;
- Sedimentation – Decantation, to separate the biomass from purified water.
The continuous biological plants, individually or in combination with other technologies, are used for the wastewater treatment deriving from the such sectors as: