Conventional Activated Sludge System (CAS)

A Conventional Activated Sludge (CAS) system commonly include an aeration tank, which is used for biological degradation, and a secondary clarifier (sedimentation tank), where the sludge in separated from the treated wastewater (refer to process flow diagram).

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 channeled to any of our sludge treatment solutions where energy can be recovered from the bio solids. 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.

Advantages of Conventional Activated Sludge (CAS):

  • Low installation cost (Cost effective)
  • Good quality effluent
  • Small land area requirement
  • Loss of head is small
  • Freedom from fly and odor nuisance high degree of treatment
  • Easily maintained mechanical work
  • Self-sustaining system