Cost and Performance Analysis of a Nanofiltration Membrane Pilot Plant Operated on a Surface Water Source


Operation of a membrane pilot plant for one year was conducted for the control of THM precursors in a surface water at Punta Gorda, Florida. As a requirement for pilot plant operation, pretreatment and membrane selection studies were conducted. Pretreatment studies were conducted by measuring the silt density index (SDI) and mini plugging factor index (MPFI) for the raw and alum coagulated water. These tests indicated that sand filtered raw water would produce a membrane feed water with an SDI of 1.3, which is acceptable for the operation of spiral wound membranes. The membrane selection study tested the ability of ten different membranes to control THM precursors. The FilmTec N 70 nanofiltration membrane was selected for pilot plant operation based on its ability to reduce the THMFP of the surface water at Punta Gorda below the 0.1 mg/ L MCL, as well as its rejection of total hardness and high water flux. During pilot plant operation, eight pretreatment changes and twenty membrane cleanings were performed to maintain permeate flux. The water quality produced by the membrane pilot plant reflected an improvement relative to the alum coagulation process. The dissolved organic carbon (DOC) content of the feed water was reduced by 93 percent. The trihalomethane formation potential (THMFP) was reduced from 0.880 mg/L to 0.063 mg/L, which is significantly below the 0.10 mg/L MCL. The total dissolved solids were reduced by 76 percent from 472 mg/L to 112 mg/L. Operating and maintenance (O&M) cost for a Punta Gorda membrane plant was estimated to be twice the cost of the Punta Gorda conventional alum process, $0.99/Kgal versus $1.86/Kgal. Capital costs for the newly constructed Punta Gorda alum coagulation treatment plant was estimated to be $6,971,000 compared to an estimated capital cost of $16,338,500 for a membrane plant. Although the cost of membrane operation at Punta Gorda was estimated to be twice that of a conventional plant, the water quality produced by the pilot plant was greatly superior to the present Punta Gorda finished water quality with respect to THMFP and TDS.


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Graduation Date





Taylor, James S.


Master of Science (M.S.)


College of Engineering


Civil Engineering and Environmental Sciences




161 p.



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Masters Thesis (Open Access)




Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic

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