Effect of pH and Floc Property on Disinfection By-products Pre-cursors Removal by Coagulation in Treating Low Organic Matter Surface Water

Xiao Zhan, Baoyu Gao, Defang Ma, Yan Wang, Qinyan Yue

 

ABSTRACT

Two pre-hydrolyzed coagulants, polyaluminum chloride (PAC) and polyferric chloride (PFC) were used to treat the low organic matter (OM) surface water. The coagulation performance, disinfection by-products (DBPs) precursors removal and floc properties at pH 4, 6 and 8 were investigated. The results showed that the best DOC, UV254 and DBPs precursors removal was achieved at pH 6, while the DOC and UV254 trend were different from the chlorine demand results for the low OM surface water. At pH 8, the DBPs precursors were not effectively removed as DOC and UV254 because the conditions were not favorable for precipitate formation. The differences of the PFC-flocs size were not significant in the pH range while the PAC-flocs were larger at pH 6. The flocs strength decreased with the increasing pH. The compact flocs tend to be generated at alkaline solution in the study. The preliminary study of the relationship between the floc properties and DBPs precursors removal showed that the small flocs were not favorable for DBPs precursors removal. Similarly, the compact flocs may not provide high removal efficiency on the DBPs precursors.

Keywords: Organic matter; disinfection by-products; floc property; coagulation

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doi:10.11912/jws.3.4.209-221