Abstract: Filtration apparatus (102) is provided for the treatment of waste water, sewage and/or effluent. The apparatus includes a housing (4) having at least a first filter layer (16) provided therein. The first filter layer (16) includes biological filtration-means including one or more organisms and a substrate material to filter waste water, sewage and/or effluent located thereon, passing thereover or therethrough in use. The apparatus includes at least a second filter layer (20) for filtering fluid that has passed through the at least first filter layer. The second filter layer (20) includes an absorbent material that is different to the substrate material of the at least first filter layer (16).