<；P>；PROBLEM TO BE SOLVED: To provide the technique for treating sludges such as raw sludge and digested sludge to be generated in a sewage treatment plant, bottom sludge and sludge being lees of Shochu (Japanese spirits) by using an inexpensive, safe and easy method. <；P>；SOLUTION: Powder of tuffaceous sandstone, andesite or andesitic tuff or crushed waste tile, which are troublesome when treated, is fed to a mixer together with sludges and agitated/mixed. The water content of the obtained mixture is decreased. The water content-decreased mixture is granulated, dried and fired to obtain a porous material usable as a filter medium, a cleaning material, a soil improving material, a roadbed material, a substitute of agricultural soil or the like. <；P>；COPYRIGHT: (C)2008,JPO&INPIT
