A coarse treatment system in which wastewater is trickled over a bed of stones or other material covered with bacteria that break down the organic waste and produce clean water.

An oxidative process for the treatment of sewage; liquid sprayed onto a rock bed is oxidised by microbes growing on the rock surface.

An attached growth biological process in which the microbial film is attached to non-moving rock or plastic media.

a bed of gravel media over which pretreated wastewater is sprayed

a bed of gravel or pebble media through which clarified effluent percolates and microbial activity removes BOD, suspended solids and ammoniacal nitrogen

The process of having the wastewater pass thru a filter to hold back and digest any remaining solid materials or paper. This protects the drainage filed or dispersal site from accumulation of solids and prevents clogging of the drain pipes.