Effect of humic acid on the removal of low-MW organic precursors in the coagulation process

• Main Authors: Hsiao-Yun Yeh, 葉曉芸
• Other Authors: Pen-Chi Chiang
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/29774765079214123870

碩士 === 國立臺灣大學 === 環境工程學研究所 === 92 === The objectives of this study were intended to evaluate the effects of model compounds on coagulation performance and DBP formation, understand the effects of humic acids and divalent cation (Ca2+) on the removal of low-molecular-weight model compounds, i.e., phloroglucinol, resorcinol, and p-hydroxybenzoic acid, determine the mechanisms associated with model compounds in the coagulation process, assess the chlorine decay rate during chlorination, and formulate the predictive HAA and THM formation model. The results of this investigation revealed that coagulation with 40 mg/L alum at pH 5 was effective for reduction of humic and tannic acids. On the other hand, low-molecular weight organics, i.e., phloroglucinol, resorcinol, and p-hydroxybenzoic acid, were unfavorable to coagulation. For mono-compounds, the DOC removal model could express the DOC adsorption onto metal hydroxide flocs and resulted in providing an accurate prediction of DOC removal during the coagulation process. For the bi-compounds of humic acid and phloroglucinol (or p-hydroxybenzoic acid), with the ratio 4:3 of humic acid to low-MW model compounds and the addition of 80 mg/L Ca2+, the DBP were efficiently reduced. It was also observed that Ca2+ was not actively reacting with model compounds and resulted in providing poor performance. For the bi-compounds of humic acid and resorcinol, the different treatments, i.e., various ratios of humic acid to resorcinol exhibited no significant influence on coagulation improvement and DBP reduction. The developed model - DBP = γ*Co {1 - ƒ*e-krt - (1 - ƒ)*e-kst} – was successful in predicting the level of DBP formation in the presence of the bi-compounds of humic acid and phloroglucinol (or p-hydroxybenzoic acid). The chlorine consumption could be adopted as an indicator because it was highly correlated with DBP formation.