Patent ID: 7264715

Claim:
A sludge treatment apparatus comprising: an anaerobic digestion tank for receiving a sludge mixed liquor formed in a biological treatment system for organic wastewater to effect the digestion of sludge and, simultaneously, the formation and growth of magnesium ammonium phosphate crystal particles; a magnesium source feeder for feeding a magnesium source to the anaerobic digestion tank; a sludge withdrawal pipe for withdrawing a sludge mixed liquor from the anaerobic digestion tank; a solid-liquid separator for receiving the sludge mixed liquor withdrawn from the anaerobic digestion tank through the sludge withdrawal pipe and separating and recovering solids containing the magnesium ammonium phosphate crystal particles; piping for returning part of the sludge mixed liquor after separation and recovery of the magnesium ammonium phosphate crystal particles to be recovered from the solid-liquid separator to the anaerobic digestion tank; and a dehydrator for dehydrating part of the sludge mixed liquor after separation; and piping for sending part of the sludge mixed liquor, after separation, from the solid-liquid separator to the dehydrator.