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 approximately 25,000 customers. The plant has operated well over the past 40 years. However, stricter regulations coupled with concerns over aging filtration underdrains motivated city personnel to consider alternative filtration technologies to provide the best quality drinking water 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 needed to determine which type of membrane filtration system would 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.

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