Treating high-turbidity water using full-scale floc blanket clarifiers

W. W. Lin*, S. S. Sung, L. C. Chen, H. Y. Chung, C. C. Wang, R. M. Wu, D. J. Lee, Ch-Hpin Huang, R. S. Juang, X. F. Peng, Hsi Lih Chang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Dynamic responses of the blanket in full-scale flat-bottom type floc blanket clarifiers at the PingTsan Water Works, Taiwan Water Supply Corporation, were monitored given a step-change in coagulant (polyaluminum chloride, PACI) dosage. The blankets in the clarifiers were easily washed out using the conventional coagulation-clarification process (the "single-stage process"), seriously threatening drinking water quality. Consequently, the PingTsan Water Works included a pretreatment stage before the single-stage process to enhance treatment efficiency. The performance of this full-scale "two-stage process" for treating high-turbidity storm water was monitored on November 9 to 10, 2000. The two-stage process achieved a stable blanket and good quality clarified water that was insensitive to variation in raw water turbidity or PACI dose. Pilot tests were also conducted on October 6 to 7, 2001 to reveal performance differences between the single-stage and two-stage processes in dealing with high-turbidity water. The single-stage process yielded a blanket that was sensitive to PACI change. Not only was the produced blanket easily washed out when the PACI dose was step-decreased, it was also slow to recover when the chemical dosage was returned to its original value. The blanket yielded by the two-stage process was more robust to low coagulant dose, and recovered more easily when coagulant supply was increased. Applying the two-stage process to achieve the same effluent quality from single-stage process could significantly reduce total PACI dosage.

Original languageEnglish
Pages (from-to)1481-1487
Number of pages7
JournalJournal of Environmental Engineering
Issue number12
StatePublished - 1 Dec 2004

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