Aerated ponds are aerobic wastewater treatment ponds (also called waste stabilisation ponds) in which the natural oxygenation is enhanced by mechanical or diffused air injection to achieve high rates of organic degradation and nutrient removal. Aerated ponds can treat almost all wastewater as long as they are biodegradable. Dependent on the type of treatment, a pre-treatment unit is required (e.g. settling, screening, etc.). If completely mixed, the aerated ponds also require a sedimentation step at the output. The process set-up is then in essence similar to activated sludge systems without sludge return.