Effects of source water location, season, and nanofilter type on permeate water quality
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abstract
Results from Information Collection Rule nanofiltration studies representing various source waters and membranes are analyzed to gain insights into the effects of source water location, season, and membrane type (composition). In the range of experimental conditions investigated, membrane type appears to have a stronger influence on contaminant removal when compared to source water location and seasonal variations. Therefore, the extent of site-specific demonstration studies currently required by state primacy agencies prior to regulatory approval of each nanofiltration installation might be limited to issues other than permeate water quality subsequent to conducting just one pilot study with the membrane under consideration. Intrinsic membrane transport coefficients for all organic water-quality parameters evaluated were highly correlated with each other, demonstrating that the solution and diffusion characteristics of natural organic matter (measured as dissolved organic carbon and/or ultraviolet absorbance at 254 nm) in the polymer phase of nanofiltration membranes are similar to those of disinfection by-product precursors. Therefore, these nonspecific measurements can be employed as excellent surrogates for trihalomethane, haloacetic acid, and total organic halide precursors even in nanofiltration systems. Permeation coefficients for inorganic contaminants (except alkalinity) were also highly correlated with each other. Permeation coefficients for inorganic and organic contaminants followed lognormal distributions at the 99% confidence level (except for calcium hardness removal by one membrane).
