Abstract: Method and apparatus in which a biomass is carried on a substrate that is fluidised. The fluidised substrate has a layer of distributor particles below it, through which the fluidizing medium passes prior to contact with the fluidised substrate and biomass associated therewith. The effect of the distributor layer is that the particles damp out excessive turbulence in the fluidizing medium, thus preventing undue turbulence of the medium within the fluidised layer. The particles may be recycled through the distributor layer to strip excess biofilm from the substrate particles prior to returning the substrate particles to the fluidised bed.

Abstract: Method and apparatus (8) in which a biomass is carried on a substrate which is fluidised. The fluidised substrate has below it a lazer of distributor particles through which the fluidising medium passes prior to contact with the fluidised substrate and biomass associated therewith. The effect of the distributor layer is that the particles damp out excessive turbulence in the fluidising medium thus preventing undue turbulence of the medium within the fluidised layer. This has the advantage of controlling, to some extent, the thickness of the biofilm, which may be carried by the fluidised substrate particles. The particles may be recycles (1, 2, 5) through the distributor layer where the action of the distributor particles serve to strip exces biofilm from the substrate particles which latter are then returned to the fluidised bed.