Pilot-Scale Evaluation of Chemical Cleaning Protocols for Organic and Biologically Fouled Microfiltration Membranes

Abstract

The Edward C Little Water Recycling Facility (ECLWRF) is the largest high-purity water recycling facility in the United States. Here, microfiltration (MF) membranes play a critical role in treating the secondary effluent and serving as pretreatment to the downstream reverse osmosis systems. New chemical clean-in-place (CIP) formulations were evaluated through pilot-scale tests for their ability to improve the performance restoration for the Phase III continuous MF (CMF) membranes at the ECLWRF. Membrane autopsies found that the primary fouling mechanisms for the CMF membranes were biological and organic in origin. It was also determined that the current CIP protocol provided an incomplete removal of the biological and organic foulants. The cleaning test results found that the current CIP regime for the Phase III system performed better than the four commercially available cleaning solutions evaluated here. However, improved results were obtained when hydrogen peroxide was added to the current CIP regime consisting of caustic soda and the commercially available Memclean C cleaning solution. The effects of the addition of hydrogen peroxide to the standard cleaning procedure shows some promise; however, further research is needed to understand the cleaning mechanisms and long-term effects of using hydrogen peroxide as a cleaning additive.