Conventional Activated Sludge (CAS) units are the most widely employed wastewater treatment technology used worldwide. This technology, which has been around for decades and was improved and refined in South Africa is still very applicable.

 A very cost effective and a reliable method of biological treatment of organic effluents. The main stages of the system are anaerobic, aerobic and anoxic which ends with clarifiers. The treated effluent is disinfected with an oxidant such as chlorine.