Removal of phosphate from municipal sewage by high gradient magnetic separation

Abstract

The removal of phosphate from municipal sewage by high gradient magnetic separation using aluminium sulphate as precipitating agent and Fe₃O₄ as seeding material was studied. The effects of aluminium sulphate, Fe₃O₄, magnetic field intensity, pH value and flow-rate of sewage on phosphorus removal rate were investigated. The results show that addition of 200 mg/L Al₂(SO₄)₃ · 18H₂O and 300 mg/L Fe₃O₄, magnetic field intensity of 200 kA/m, pH value of 4.5 – 7.0 and flow-rate of 6.15 cm/s are both efficient and economic technical parameters for removal of phosphate. The pH value has a tremendous effect on the removal of phosphate. In the pH range of 4.5–7.0, more than 95% phosphate can be removed. Theoretical analysis indicates that the solubility of AIPO₄ is minimum at pH 4.0 – 7.0 and the electrostatic attractive force between AIPO₄ and Fe₃O₄ is maximum at pH 4.5 – 6.5.

Keywords

removal / phosphate / municipal sewage / high gradient magnetic separation

References

[1] KubaT. Phosphorus and nitrogen removal with minimal COD required by integration of denitrifying dephosphorization and nitrification in a two-sludge system[J]. Wat Res, 1996, 30(7): 1702-1710

[2] LiuZhi-qiang, MiaoQun, ZhangJian. Review on the technology of biological nitrogen and phosphorus removal from municipal sewage[J]. Journal of Qingdao Institute of Architecture and Engineering, 2003, 24(3): 64-67(in Chinese)

[3] LONG Teng-rui. Study on nutrient removal from continuous intermittent aeration process[J]. China Environment Science, 2000, (4): 366–370. (in Chinese)

[4] HeLi-ping. Technological research on urban waste water treatment by diatomite[J]. Yunnan Environmental Science, 2002, 21(2): 60-61(in Chinese)

[5] LiGui-ping, LuanZhao-kun. The study of phosphorus removal for secondary effluent in advanced municipal wastewater treatment using microflocculation-direct filtration[J]. Techniques and Equipment for Environmental Pollution Control, 2002, 3(4): 65-68

[6] ZhouKe-zhao. Treatment of municipal wastewater with biological/chemical (BC) process [J]. China Water & Wastewater, 2000, 16(10): 13-17(in Chinese)

[7] Kolm H H. Magnetic Device [P]. US patent, 3567026. 1971-03-02.

[8] HarlandJ R, NilssonL, WallinM. Pilot-scale high gradient magnetic filtration of steel mill waste [J]. IEEE Trans Magn, 1976, 4: 904-907

[9] YingT Y, YiacoumiS, TsourisC. High-gradient magnetically seeded filtration[J]. Chemical Engineering Science, 2000, 55: 1101-1113

[10] SongJin-pu, ZhangShan-wen, YuLin, et al.. Research on removing bacteria with high gradient magnetic filter[J]. Journal of Harbin University of Architecture and Engineering, 1996, 29(5): 101-104(in Chinese)

[11] TerashimaY, OzakiH, SekineM. Removal of dissolved heavy metals by chemical coagulation, magnetic seeding and high gradient magnetic filtration[J]. Wat Res, 1986, 20(5): 537-545

[12] AhamadM, ShaikhH, DixitS G. Removal of phosphate from waters by precipitation and high gradient magnetic separation[J]. Wat Res, 1992, 26(26): 845-852

[13] AnninD E, JamesA R, HaryJ P, et al.. New magnetic field-enhanced process for the treatment of aqueous wastes[J]. Separation Science and Technology, 1999, 54: 1277-1300

[14] BookerN A, BrooksR B. Scale up of the rapid sewage treatment sirofloc process[J]. Process Safety and Environmental Protection (Transactions of the Institution of Chemical Engineering part B), 1994, 72B: 109-112

[15] ZhangXiang-lin, KangHengCoordination Chemistry[M], 1986, Changsha, Central South University of Technology Press: 106-107(in Chinese)