A method for treating a fluid is provided using a particulate material in the form of a deposited layer having an upstream side and a downstream side wherein a flow of the fluid is directed through the deposited layer from the upstream to the downstream side at a first temperature. The method includes reconditioning the deposited layer and then resuming treatment of the fluid, wherein reconditioning comprises heating the deposited layer to a second temperature; and cooling the deposited layer to a third temperature at an average cooling rate in the range of up to about 20° C./min.