AWWA MTC57578

The City of Vero Beach, Florida has successfully operated their 2-MGD Reverse Osmosis (RO) facility for the past 11 years with the originally installed membrane elements. In recent years, membrane performance has decreased and feed pressures have increased significantly. Although the membrane elements were chemically cleaned and the cleaning provided an effective short-term solution to the performance problems, the membranes returned to their pre-cleaning condition in less than three months. Based upon the rapid decline in the membrane performance and age of the membranes, the City elected to replace the membrane elements. Three manufacturers of 8-1/2 inch thin film composite membranes were tested side by side on the identical feed water quality. The design of the membrane skid allows for a full-scale demonstration of seven 8-1/2 inch membrane elements to be loaded into full-length pressure vessels. The full-scale test evaluated the physical operating parameters and chemical analysis of the feedwater, permeate, and concentrate. This paper focuses on the performance of the three membranes in the full-scale tests. Comparisons between permeate quality for all three different membrane manufacturer elements is shown. Capital cost projections based on the feed pressures required will be the major criteria in the final selection criteria. The importance of conducting a full-scale membrane test for several months is a main theme of the paper. Analysis of the changes in performance of the membranes is performed. Another main theme of the paper is selecting a membrane based upon proven performance and not only computer-simulated projections. There was disparity between computer projections and actual performance data. Slight differences in surface area and feed pressures yielded significant performance differences. Includes 3 references, tables, figures.