According to {HEAD ~ a variant} of {TAIL ~ this embodiment}, it can also be advantageous, to improve the life of the beds, to insert between the activated carbon bed and sand bed a layer of a third granular material with a density between that of activated carbon and sand, for example, anthracite 
of
According to { HEAD ~ a variant } of { TAIL ~ this embodiment } , it can also be advantageous , to improve the life of the beds , to insert between the activated carbon bed and sand bed a layer of a third granular material with a density between that of activated carbon and sand , for example , anthracite
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH