Apparatus for treatment of waste water

An apparatus is provided for treatment of organic contaminant containing waste water such that the oxygen demand of the waste water is reduced and methane is produced. The apparatus comprises an anaerobic digester or filter. The digester is packed with a media which provides a substantial growth surface area to microorganisms contained within the digester. The digester also includes recirculation means whereby fluid in the digester below the media is recirculated directly to an upper portion of the digester. Furthermore, the digester has effluent overflow outlets which outlets include a trap to prevent oxygen from entering the digester from the atmosphere. Fluid to be treated in the digester enters the upper portion thereof, passes downwardly through the media, is recirculated by the recirculating means to an upper portion of the digester, and exits the digester after treatment by the microorganisms therein through the outlets. The recirculating means may be selectively adjusted to vary flow in different portions of the digester.