AWWA MTC61107

A 20 MGD water treatment facility, designed and constructed in the early 1990s was slated for a significant hydraulic expansion to 42 mgd. The design was to be executed with the Long Term 2 Enhanced Surface Water Treatment Rule (LT2) requirements looming on the horizon. The Owner desired to provide the expansion facilities while simultaneously integrating new process elements capable of assuring compliance with the worst case Cryptosporidium inactivation/removal requirements of LT2. Two process trains were considered for expansion, conventional clarification/filtration with ultraviolet (UV) disinfection versus conventional clarification with membrane filtration. Both options would be capable of meeting the disinfection requirements of source water classified in Bin 4 and requiring 5.5 log Cryptosporidium removal/inactivation value, if necessary. The clarification/membrane filtration process was selected based on a relative cost comparison, site considerations favoring a smaller footprint and preservation of space for subsequent expansions, and consideration that a highly effective removal capability was preferable to a specific microbe targeted inactivation process. This paper describes selection and procurement considerations critical to integration of membrane filtration into the existing process train. The proposed design is illustrated. Includes tables, figures.