Abstract: The invention includes an anaerobic solids digestion apparatus comprising a digester, at least one draft tube; at least one nozzle and a biogas source; a method for digesting a waste stream in an anaerobic solids digestion apparatus comprises feeding a waste stream to a digester; reacting the anaerobically biodegradable material in the waste stream with anaerobic bacteria in the digester; introducing a mixed liquor into the digester and mixing the mixed liquor; and a method for minimizing the use of inhibitory polymers by concurrently digesting and concentrating the mixed liquor in the digester.