Abstract: Abstract of the Disclosure A porous composite block for fluid treatment is described. The block has at least two stages or portions in fluid communication with one another; a first portion and a second portion located upstream of the first portion. Both the first portion and the second portion can contain one or more active particle types. The first portion contains a binder and first active particles of a predominant first active particle type. The first active particles have a first particle size. The second portion contains a binder and second active particles of a second active particle type. The second particle size is smaller than the first particle size. In some arrangements, the second particle size is less than about 50 ?m. In some arrangements, the second particle size is less than about 1 ?m.