Membrane effects during filtering investigation of membrane effects during filtering of natural surface waters in Missouri

Abstract

Previous work has demonstrated that suspended clay accumulating on filter paper can act as a membrane and affect chemical concentrations in the filtered water. For this reason, we looked at the possibility of membrane effects altering water chemistry during filtering for Missouri Rivers. Membrane effects during filtering could cause an initial decrease in sample concentrations as the filter cake began acting as a membrane, with a corresponding increase of concentration as the concentration polarization layer was formed behind the filter cake. Samples from five Missouri rivers were tested: the Mississippi River at St. Louis, the Missouri River at Kansas City, the Gasconade River at Jerome, the Osage River at the junction of Highway 63 and 50, and the Meramec River one mile downstream from springs. Three 1-l samples were filtered from each river using a 0.45 lm filter. An unfiltered sample from each river underwent dialysis to determine the actual ion concentrations of the overall sample. None of the filtered samples demonstrated a statistically significant alteration of water chemistry using current filtering techniques in this preliminary study, suggesting that membrane effects due to accumulation of clay particles on filter paper may not be a common problem in Missouri and similar regions.

Filter Membrane Effects on Water‐Extractable Phosphorus Concentrations from Soil

“…Filtration of water and soil solution samples for various analytical methods is necessary because suspended solids can damage equipment and interfere with chemical analysis (Saindon and Whitworth, 2006), and because the dissolved fraction is considered to be the most mobile and bioavailable (Sharpley and Smith, 1993). The dissolved fraction of aqueous solutions is most commonly defined as the portion that passes through a 0.45‐μm‐pore‐sized filter membrane (Pote and Daniel, 2009), although some researchers use a 0.2‐μm filter (Worsfold et al, 2005).…”