AWWA MTC64626

The City of Murfreesboro Water and Sewer Department (MWSD) currently operates a 15.6 MGD Lime Softening/Mixed Media Filtration plant to provide drinking water to its approximately 25,000 customers. Although the plant has operated well over the last 40 years, increasingly tight regulations coupled with concerns over aging filtration underdrains motivated City personnel to consider alternative filtration technologies to provide the best quality drinking water possible to its customers. The decision was made in 2004 to rehabilitate the existing treatment processes, and to include membrane filtration in the updated process scheme. City personnel and engineering consultants wanted to determine which type of membrane filtration system best fit the City's needs, and the configuration in which the membranes should be placed. At issue was whether to use a vacuum driven, immersed membrane technology or a pressure driven, containerized design. Also at issue was whether the membranes should be installed before or after Granular Activated Carbon (GAC) filtration. In the end, the Murfreesboro Water and Sewer Department (MWSD) selected a pressurized, containerized membrane filtration system. In order to provide maximum flexibility for the renovated plant, a piping system was designed that would allow the membranes to operate either before or after GAC filtration. This should allow the treatment plant staff to determine the advantages and disadvantages of each operational mode on the full-scale plant, and make their own determination using real-world data. This paper discusses several of the factors considered during the evaluation of both membrane technologies. The results of four months of pilot testing on the selected system are also discussed. Includes tables, figures.