Mineral substances such as sand, gravel, grit, stones etc. are also washed in via various wastewater discharges in sewer systems.
These mineral substances, mixed with wastewater components, form the so-called debris. If this debris is not removed/filtered from the circuit, the abrasive effect of the medium can cause severe mechanical damage, blockages and heavy wear to the downstream wastewater treatment systems and components.
Aerated debris shafts serve as a coarse filter and separation system for organic and mineral components.

Coarse-bubble aeration promotes the buoyancy of substances through air bubbles and thus separates organic material from the mineral (flotation). The organic particles are transported to the wastewater treatment plant. This effectively prevents putrefaction processes and greatly reduces the load on rainwater overflow basins and sewage treatment plants. The mineral components are retained in the debris shaft and can be removed with clearing equipment when they reach the appropriate level. The dry weather runoff should be routed through the system in a stationary dry weather channel.