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Title:
METHOD FOR REMOVING PHOSPHORUS IN WASTEWATER
Document Type and Number:
WIPO Patent Application WO/2004/071970
Kind Code:
A1
Abstract:
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.

Inventors:
AOKI ROKUROU (JP)
INAGAKI HAJIME (JP)
Application Number:
PCT/JP2004/001417
Publication Date:
August 26, 2004
Filing Date:
February 10, 2004
Export Citation:
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Assignee:
NIPPON CHEMICAL IND (JP)
HIPOTECH INC (JP)
AOKI ROKUROU (JP)
INAGAKI HAJIME (JP)
International Classes:
C02F1/58; B01D9/02; C02F1/52; C02F1/66; (IPC1-7): C02F1/58; B01D9/02
Foreign References:
JPH02164493A1990-06-25
JPH04150996A1992-05-25
JP2001129560A2001-05-15
JP2002348106A2002-12-04
JPS57187092A1982-11-17
Attorney, Agent or Firm:
Akatsuka, Kenji (5F 1-16, Kanda Suda-ch, Chiyoda-ku 41, JP)
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