| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 91 === After chlorination in water purification processes, the organics in the water would form disinfection byproducts (DBPs) which would cause cancer risk. The organics removal performance is limited by traditional coagulant such as alum or ferric salt. The research investigates the organics removal rate by polymer in coagulation and flocculation. The organics sources are from water reservoirs and artificial water composed by Aldrich humic acid to study the removal effectiveness by polymer under different pH and turbidity with addition of kaolin.
The results show that when polymer is used as coagulant, the removal rates of turbidity and total organic carbon (TOC) are worse than aluminum sulfate. So the polymer is not suited for coagulant. By using polymer as coagulant aids, PDADMAC series have better TOC removal rates. Through surface charge analysis, the floc formed by aluminum sulfate is still negative. PDADMAC is positive charged polymer. Both attract by static electricity to agglomerate to floc which precipitates faster and TOC removal rate is enhanced. Smaller molecular weight (MW) PDADMAC-s has best TOC removal rate under pH 6 and 50~100 NTU. It increases the TOC removal rate about 10~15 % of Fongshan reservoir water and 50 % of Chenggong reservoir water. For Aldrich humic acid composed by higher MW of organics, PDADMAC-s increases about 20 % of TOC removal rate.
Through Gel Permeation Chromatography (GPC) analysis, the organics MW distributions are almost under 2,000 dalton after coagulation by aluminum sulfate and have very little discrepancy after the addition of PDADMAC-s. This means that the organics MW are small (under 2,000 dalton) and are more hydrophilic. PDADMAC-s doesn’t adsorb and remove the organics directly. Additional turbidity has to be added to increase the suspended solids, in order to increase the solid surface for organics to adsorb on. And the suspended solids become the medium for polymer agglomeration. That results in the increase of TOC removal rate.
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