Abstract: A packing element for use as a biofilm support in the biological processing of liquids. The packing element has a hollow cylindrical body having a plurality of helical blade members extending generally radially from the cylindrical body. A plurality of such packing elements are placed in a vessel. When liquid and/or gas flows over them, they tend to rotate causing local turbulence with resulting improvement in diffusion of gas and/or substrate to and from the biofilm, giving enhanced rates of liquid processing.