AWWA MTC61116

The City of Minneapolis' 70-MGD Columbia Heights Membrane Filtration Plant is currently under construction, with start-up of the plant scheduled for the spring of 2005. As part of the preparations for start-up, the City has continued pilot testing the Ionics/Norit ultrafiltration system since the system's procurement in 2001. The focus of this paper is on the lessons learned during this extensive piloting at Minneapolis, and in particular, on the recent piloting results, during which pilot testing was approached with full-scale operations as a control factor. All experiments done on the pilot must be capable of being implemented in the full-scale plant. The end result of the extensive pilot testing has been the development of improved maintenance and recovery cleaning procedures and modifications to the sequencing of the direct integrity test (DIT), which are being incorporated into the full-scale plant's operational toolbox. The extensive piloting effort at Minneapolis following procurement has afforded the City the opportunity to identify and troubleshoot potential operational issues and make necessary modifications into the plant design. Such issues can be difficult to identify during short-duration pilot testing (used for the purposes of procurement), particularly with the dynamic nature of surface water quality throughout the course of a year. For the Columbia Heights Membrane Plant pilot units, three primary issues were identified during post-procurement pilot testing: what is the "clean" membrane permeability and what is a reasonable permeability to sustain during normal operation; fouling of the membrane system starting in the spring, during the snow melt run-off period and lasting sometimes into fall; and, the impacts of the direct integrity test (DIT) on the membrane permeability. Includes reference, table, figures.