AWWA MTC64550

This slide presentation outlines a study on comparing the effectiveness of microfiltration (MF) vs. ultrafiltration (UF) pretreatment on nanofiltration (NF) and reverse osmosis (RO) membrane performance related to water quality, fouling rates, and virus rejection. The study also autopsied high-pressure membranes to evaluate foulant accumulation, and developed bench-scale tests to measure the effect of operating conditions on long-term fouling related to backwash, FeCl₃ dose, and foulant accumulation. Experimental methods included: MF/RO and UF/RO operated in parallel; monitored flows and pressures; periodic measurement of water quality (WQ) parameters; simultaneous bench-scale testing; virus challenge studies; and, membrane autopsy at end of study. A program at the North Buffalo WRF in Greensboro, North Carolina is outlined. Conclusions drawn included: less RO fouling by UF than MF pretreatment; extent of RO fouling is still significant; polysaccharides implicated as foulant, though little difference in dissolved organic carbon (DOC) rejection between UF and MF; colloidal removal by FeCl₃ in UF not understood; 4-5 log removal of virus by RO, but virus found in some permeates; virus removal increases with fouling of MF and UF; membrane permeate quality suitable for many reuse applications; and, additional work necessary to evaluate engineering significance of results. Includes tables, figures.