AWWA JAW39582

The influence of natural organic matter (NOM) composition on the rejection of total organic carbon (TOC), permeate water flux, and the strength and amount of NOM association with the membrane was examined in bench-scale nanofiltration studies. NOM composition was manipulated by fractionation into hydrophilic and hydrophobic components and by powdered activated carbon (PAC) pretreatment with subsequent dilution to control for TOC concentration. Hollow-fiber nanofilters made of negatively charged polysulfone were used in a batch recycle system. Hydrophobic NOM was shown to be responsible for nearly all permeate flux decline and was more highly rejected by the membrane than hydrophilic NOM. Using membrane-feed solutions with the same TOC concentration, the authors found that the NOM remaining in solution after PAC pretreatment caused greater permeate flux decline and was more poorly rejected than the original mixture of NOM. NOM recovered from the membrane after nanofiltration was predominately high-molecular-weight material (i.e., >30,000 daltons). Includes 23 references, tables, figures.