Acetic acid, Aluminum sulfate, Citric acid, Coagulation, Drinking water -- Purification, Ferric chloride, Ultrafiltration, Water -- Purification -- Filtration
Integrating ultrafiltration (UF) membranes in lieu of traditional media filters within conventional surface water coagulation-flocculation-sedimentation processes is growing in popularity. UF systems are able to produce low turbidity filtered water that meets newer drinking water standards. For typical drinking water applications, UF membranes require periodic chemically enhanced backwashes (CEBs) to maintain production; and citric acid is a common chemical used for this purpose. Problems may arise when the backwash recycle stream from a citric acid CEB is blended with raw water entering the coagulation basin, a common practice for conventional surface water plants. Citric acid is a chelating agent capable of forming complexes that interfere with alum or ferric chloride coagulation. Interference with coagulation negatively affects settled water quality. Acetic acid was investigated as a potential substitute for citric acid in CEB applications. A jar testing study was conducted to compare the impacts of both citric acid and acetic acid on the effectiveness of aluminum sulfate (alum) and ferric chloride coagulants. Citric acid was found to adversely affect coagulation at lower acid to coagulant (A/C) molar ratios than acetic acid, and a coagulation interference threshold was identified for both acids based on settled water turbidity goals recommended by the U.S. Environmental Protection Agency (EPA). Pilot testing was conducted to assess the viability of acetic acid as a UF CEB chemical. Acetic acid CEBs maintained pilot performance in combination with sodium hypochlorite CEBs for filtering a raw California surface water. It is believed that this is the first ultrafiltration membrane process application of acetic acid CEBs for municipal potable water production in the United States.
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Duranceau, Steven J.
Master of Science (M.S.)
College of Engineering and Computer Science
Civil, Environmental, and Construction Engineering
Length of Campus-only Access
Masters Thesis (Open Access)
Dissertations, Academic -- Engineering and Computer Science, Engineering and Computer Science -- Dissertations, Academic
Boyd, Christopher C., "Effect Of Acetic Or Citric Acid Ultrafiltration Recycle Streams On Coagulation Processes" (2011). Electronic Theses and Dissertations. 2012.