A Trickling Filter consists of a rotating arm that sprays wastewater over a filter medium. The filter medium can consist of rocks, plastic, or other material. The filter material is coarse, allowing air to flow through the media. This process does not actually filter material out, however.
Bacteria grow on the filter material.
The bacteria then absorb and consume the waste as it trickles through the filter, improving the quality of the wastewater. The water is collected at the bottom of the filter for further treatment.