Treating high-turbidity water using full-scale floc blanket clarifiers
Journal
Journal of Environmental Engineering
Journal Volume
130
Journal Issue
12
Pages
1481-1487
Date Issued
2004
Author(s)
Lin W.W.
Sung S.S.
Chen L.C.
Chung H.Y.
Wang C.C.
Wu R.M.
Huang C.
Juang R.S.
Peng X.F.
Chang H.-L.
Abstract
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. © ASCE.
SDGs
Other Subjects
Potable water; Sensitivity analysis; Turbidity; Water supply; Chemical dosage; Pilot tests; Polyaluminum chloride (PACL); Single-stage process; Dynamic response; coagulation; sludge blanket clarifier; turbidity; wastewater treatment
Type
journal article