33. An apparatus for the biological removal of phosphorus from raw water, the apparatus comprises: an anaerobic tank into which the raw water and activated sludge are introduced to form a mixed liquor, an aerobic tank in which the mixed liquor from said anaerobic tank is aerated, first solid/liquid separating means in which the mixed liquor flowing out of said aerobic tank is subjected to solid/liquid separation, means for returning at least some of the solid/liquid separated sludge from said first solid/liquid separating means as the activated sludge to the anaerobic tank,second solid/liquid separating means in which some of the mixed liquor discharged from the anaerobic tank is subjected to solid/liquid separation, means for returning at least some of the solid/liquid separated sludge from said second solid/liquid separating means to at least one of the anaerobic tank and the aerobic tank, solubilizing means for solubilizing at least some of the sludge separated in the second solid/liquid separating means, a fermentation tank, into which at least some of the sludge which has been solubilized is introduced and subjected to a fermentation treatment, means for supplying solubilized sludge to the fermentation tank, means for returning at least some of the sludge subjected to the fermentation treatment to the anaerobic tank, and phosphorus-removing means with which phosphorus is removed from water which has been separated in the second solid/liquid separating means.
34. The apparatus of claim 33, wherein at least some of the sludge separated in said second solid/liquid separating means is returned to both the anaerobic tank and the aerobic tank.
35. The apparatus of claim 33, further comprising means for returning at least some of the solubilized sludge to the second solid/liquid separating means.
36. The apparatus of claim 33, further comprising a means for supplying at least some of the sludge subjected to the fermentation treatment to the second solid/liquid separating means.
37. The apparatus of claim 33, further comprising means for supplying raw water to the fermentation tank.