The Process And Mechanism Study For The Municipal Sewage Treatment By Magnetic Flocculation And High Gradient Magnetic Separation

Nowadays, municipal sewage treatment and its outflow recycling have become one of the most urgent unsettled problems But the two-stage biology process which is mainly used in municipal sewage treatment in our country, has some shortcomings as follow: (1) long flow small flux and too much room occupation (2) its outflow can't attain to the first degree discharge standard of pollutants for municipal waste water treatment plant of the national(GB 18918-2002). If the phosphorus in the outflow should <0.5mg/L, further chemical disposal must be needed.On the base of the analysis of current technology used in municipal sewage treatment, the tentative idea of treating municipal sewage using magnetic flocculation and high gradient magnetic separation was first proposed. In this paper, firstly, the mechanism of magnet in magnetic chemical flocculation of phosphorus removal has studied in laboratory. The result showed that the magnet has two effects in magnetic chemical flocculation, one is as a medium to combine the A1PO4 and strengthen the precipitation of the sediment, the other one is heighten the separation efficiency by enduing the deposit with magnetism. Then the scale-up experiment was carried out to find out the best parameters on industrial HGMS. The result shows: the process has special effort on heavy metal removal, and the bacteria were mainly be killed. It can greatly reduce the BOD COD and SS in the municipal sewage36-90%CODCr and >95% phosphorus can be removed in the best parameter ( Fe3O4 0.3g/L, magnetic field 0.2T, A12(SO4)3 200mg/L, PAM 2mg/L, velocity of flow 60-100m/h). And the outflow can attain to the first degree discharge standard of pollutants for municipal waste water treatment plant of the national(GB 18978-2002). (The inflow: CODCr 154.6mg/L BOD5 46.4mg/L SS64.4mg/L P 0.58mg/L, The outflow: CODCr 58.2mg/L. BOD516.3mg/L SS 25.2mg/L, P<0.03mg/L; The first degree of GB18978-2002: CODcr, 60 mg/L, BOD5 20 mg/L SS 20 mg/L. P 0 5mg/L) When the inflow CODcr, 80mg/L, P 2.05mg/L, the outflow CODcr can attain to 45mg/L, P canattain to 0.03mg/L, the decontamination efficiency can reach 43% and 98%.Combining the high efficiency of the chemical removal of phosphorus and large inflow of HGMS, the magnetic flocculation and high gradient magnetic separation process have some special advantages in treating municipal sewage: large flux small room occupation simple facility easy to realize incorporation and automation, especially in phosphorus removal. The process which can be widely used in many fields, especially in following three aspects: community or minor city sewage treatment, enlargement of major city sewage treatment plant and the deep treatment of outflow from sewage treatment plant will have a promising prospect in sewage treatment...