Abstract: An submersible media-filled wastewater treatment filter (18) for use with a septic tank (10) or other treatment unit utilizes a special media (30) to provide solids separation and biological treatment within the filter unit. The media is a highly compressible material with a large surface area to volume ratio. As microorganisms that provide biological treatment of the wastewater flowing therethough grow and multiply in the filter media, the pores of the media may become clogged with biomass and require flushing. The filter provides for in place regeneration of the media. For example, a tool (38) can be used from above the ground surface to compress the media (30), thus flushing the accumulated solids out of the filter media and into the tank (10) in which it is installed.