Method for removing phosphorus in wastewater

• Main Author: AOKI ROKUROU,INAGAKI HAJIME
• Format: Patent
• Language: English
• Published: 05.09.2007
• Subjects: CHEMISTRY; METALLURGY; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; TRANSPORTING; TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

A method for removing phosphorus in wastewater, which comprises a first crystallization step of reacting, in a first crystallization vessel, a phosphorus-containing wastewater, calcium chloride and a recycled hydroxyapatite slurry recycled form a precipitation tank and crystallizing, while adjusting the pH of the reaction mixture by the use of a pH-adjusting agent, a second crystallization step of feeding the slurry formed in the first step to a second crystallization vessel, adding calcium chloride to the slurry, to carry out further reaction and crystallization at a pH higher than that in the first crystallization vessel and of 11 or lower, and a step of feeding the slurry formed in the second step to a precipitation tank, carrying out precipitation and separation, discharging a resultant supernatant to the outside of the system as a treated water, and recycling most of the resultant concentrated slurry as the above-mentioned hydroxyapatite slurry. The above method allows the removal of phosphorus in a waste water without the use of a coagulant and also the formation of a hydroxyapatite excellent in filtration and dewatering characteristics from a phosphorus-containing waste water.