AWWA WQTC69404

A recent pilot study was conducted in two phases in 2007 using a ceramic microfiltrationmembrane. The goals of the study were to consistently treat turbidity to levels below 0.05 NTUand DOC to levels less than 4 mg/L. The study was performed on various water sources thatwill ultimately contribute to the full scale reservoir estimated for completion in 2010. The ceramicmembrane system used during this study consisted of a single monolithic element with 269square feet of membrane surface area. The pilot setup included a rapid mix tank with a 20minute retention time that was directly fed to the ceramic membrane. Additional tests wereperformed with in-line coagulation with a retention time of 30 seconds. During the entire studyno form of solids settling was utilized. The flux rates operated during Phase I reflected 90 gfdwith one (1) hour filtration cycles. In Phase II the flux rates were lowered to 75 gfd with 30minute filtration cycles to address the higher solids loading contributed by the powdered activated carbon (PAC) slurry. Theinfluent water tested during the study included a surface water source, a secondary effluentreservoir and a combination of the two sources. Turbidity ranged between 2 to 300 NTU in thesurface water and less than 15 NTU in the secondary effluent source. Organic concentrations(TOC) ranged between 7 and 14 mg/L which averaged greater than 93 percent in the form of dissolved organic carbon(DOC). Specific ultraviolet absorption (SUVA) measurements were performed during the studyand reflected values consistently less than 2 L/mg-m. Phase I test consisted of enhancedcoagulation with a pH less than 6 and various forms of aluminum and iron salts. The optimumcoagulant was determined to be ferric chloride with a dose range between 60 and 100 mg/L.This combination achieved the turbidity goals and provided a maximum DOC removal of 52.6percent. In addition, PAC doses up to 80 mg/L were added directly to the membrane whichprovided an additional 14.2 percent removal. The second phase was performed with enhancedcoagulation and a PAC slurry concentration of 4,000 mg/L that was fed to the membrane. Theresults associated with this setup provided a maximum DOC removal of 91.8 percent producinga final filtrate with DOC levels less than 1 mg/L. The membrane achieved the set goals undervarious testing conditions and was able to recover transmembrane pressures equivalent to anew membrane after every clean in place (CIP) regardless of the testing parameters. Theceramic microfiltration system proved it could provide a single step solution without pretreatmentin addressing waters with difficult TOC removal demands. This level of treatment could berealized in various forms including enhanced coagulation, PAC addition, PAC slurry, directinjection, or various combinations of the techniques tested. Includes 2 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

8

File Size:

1 file , 1.1 MB