Abstract: A process for treatment of biological waste includes passing biological waste liquid downwardly through at least one substantially vertically oriented curtain having a reinforcing layer of support material. Attached thereto is at least one layer of flexible reticulated open cellular material having a plurality of communicating cells which form a support for filamentous micro-organisms and/or symbionts included in the filamentous micro-organisms. The filamentous micro-organisms and/or symbionts form a dense mat of cellular material adhering to the support. The biological waste is collected after passage through the curtain for ultimate disposal.