| ABSTRACT:This experiment measured physical properties of flocculent under different ferric coagulants dosage, using coagulation-microfiltration process with board membrane to study the humic acid removal efficiency and the influence of membrane fouling slowing. At the same time, coagulant types and dosage on membrane fouling have been investigated. The main conclusions are as follows:1) The isoelectric point of flocculent appears between 0.6 and 0.8mmol/L(dose as Fe), while the pH within 5.50～6.50. With the same dosage, FC flocculent potential is higher and rises faster than PFS's. The flocculent fractal dimension of PFS is bigger than FC, its flocculent density is larger and the slow down effect to membrane flux decline is not significantly than FC.2) Flocculent with too much or too little of coagulant are both minor, and go against the slow of membrane pollution. While flocculent size close the membrane hole can significantly increase membrane pollution.3) Results shows that water pre-coagulated by ferric coagulants before microfiltration membranes filtering can significantly improved the water quality. The coagulant dosage is proportional to the water quality, but its membrane pollution is not improved with the amount of coagulant increases. Comprehensive analysis shows that the best water flocculation conditions are not the best flocculation conditions of slow membrane pollution.4) Under the same dosage, the quality of water pre-coagulated by FC before microfiltration membranes is slightly better than PFS. In most cases (0.2～0.8mmol/L), on membrane fouling improvement by FC is better than by PFS. But dose of 1.0 mmol/L, the opposite is true, this is mainly due to the pH slashed, which affects forming the effective flocculent.
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