Removal of DBP precursors in micro-polluted source waters: A comparative study on the enhanced coagulation behavior

Abstract

In this study, the performance of enhanced coagulation for dissolved organic matter (DOM)/disinfection by-product (DBP) precursors removal in an anthropogenic micro-polluted water, Xihangdao (XD) River, were studied and compared with a well-protected natural source waters from Mopanshan (MS) Reservoir. Four types of coagulants, FeCl3, Al2(SO4)3, polyaluminum chloride (PACl) and a composite high performance polyaluminum chloride (HPAC), were selected to assess and compare the performance of coagulation to remove DOM with distinct properties. The composition of DOM were characterized using resin adsorption (RA) and high performance size exclusion chromatography (HPSEC) and results were linked with their performance in coagulation. The DOM in MS has higher portion of high molecular weight and hydrophobic DOM than that in XD, and which also has higher THMFP; in contrast, DOM in XD has higher portion of low molecular weight and hydrophilic synthetic organic contaminants, and with higher HAAFP. It results in significantly different performance of DOM and DBP precursors removal by coagulation. The coagulant demands for optimizing turbidity removal (BC) and for DOC removal (EC) were determined for the two water sources by the four types of coagulants. It indicates that although all the coagulants are more effective to remove DOM from MS than XD, the metal salts exhibited higher treatability than Al-based polymeric coagulants at EC dosage (FeCl3 significantlyoutperformsAl-basedcoagulants), and the order of utilization yield at EC was FeCl3>HPAC≈Al2(SO4)3>PACl for MS and HPAC>FeCl3>Al2(SO4)3≈PACl for XD.