A CAS system is a series of biological treatment steps that degrade the biological materials from the sewage or wastewater.
The first step of a CAS system is the aeration tank, where the wastewater is mixed with air to activate micro-organisms. While digesting the wastewater, the organisms collide with each other, forming larger particles called flocs, which have a larger capacity to degrade the biological components of the wastewater.
The aeration basin is followed by a secondary clarifier or settling tank. During this step, micro-organisms with their adsorbed organic material settle.
Water from the clarifier is transported to installations for disinfection and final discharge or to other tertiary treatment units for further purification.
The surplus micro-organisms can easily be channelled to any of our sludge treatment solutions where energy can be recovered from the biosolids. This additional step closes the energy cycle of the wastewater treatment plant allowing it to run independently of fossil fuel.
Another part of the micro-organisms is fed back into the aeration tank in order to keep the load of micro-organisms at a sufficient level for the biological degrading processes to continue.