Removal of Natural Organic Matter from Water by Coagulation and Flocculation to Mitigate the Formation of Chlorine- Disinfection By-Products at the Thu Duc Water Treatment Plant in Vietnam
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Abstract
In this study, removal of NOM to prevent the potential formation of DBP at Thu Duc Water Treatment Plant (TDWTP) in Vietnam was investigated using coagulation-flocculation. Coagulants poly-aluminium chloride (PAC), aluminium sulphate Al2(SO4)3, and ferric chloride (FeCl3) – with polyacrylamide (PAM) as the flocculant were examined. The efficiency was characterized by turbidity, total organic carbon (TOC), and total trihalomethane (TTHM). Results showed that the optimal dosage of PAC, Al2(SO4)3, and FeCl3 was 20, 10, and 20 mg/L, respectively, while a 0.05 - 0.15 mg/L of PAM was effective dosage. The optimal pH was 7.0 (PAC), 6.0 (Al2(SO4)3), and 8.0 (FeCl3). Under optimal conditions, the turbidity removal was almost 99% with all coagulants while a maximum TOC removal of 26.6% was found with Al2(SO4)3. In all cases, TTHM was not detected. Hence, Al2(SO4)3 accompany with PAM are suggested to replace PAC which is currently used at TDWTP. Although a low efficiency in TOC removal was found, it is significant to raise a suggestion to TDWTP since the water quality monitoring now does not examine NOM and DBPs issues. Furthermore, this study provides useful information for other local water plants which employ similar raw water source and treatment processes.
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