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Lyophilization and Reconstitution of Reverse-Osmosis Concentrated Natural Organic Matter from a Drinking Water Source
McCurry, D. L., T. F. SPETH, AND J. G. PRESSMAN. Lyophilization and Reconstitution of Reverse-Osmosis Concentrated Natural Organic Matter from a Drinking Water Source. JOURNAL OF ENVIRONMENTAL ENGINEERING. American Society of Civil Engineers (ASCE), Reston, VA, 138(4):402-410, (2012).
To inform the public.
Disinfection by-product (DBP) research can be complicated by difficulties in shipping large water quantities and changing natural organic matter (NOM) characteristics over time. To overcome these issues, it is advantageous to have a reliable method for concentrating NOM with minimal loss and maximum shelf-life. NOM concentration and preservation by lyophilization (freeze-drying) has been practiced for many years; however, no complete method for lyophilizing and reconstituting NOM exists in the literature. The purpose of this research was to both optimize the lyophilization process of a concentrated NOM solution and to determine the appropriate conditions (pH, mixing time, and concentration factor) under which to reconstitute lyophilized NOM for maximum total organic carbon (TOC) and ultra-violet absorbance at 254-nm (UV254) recovery. A lyophilization recipe was developed and 12 L of NOM concentrate was lyophilized. Lyophilized NOM was then reconstituted in 36 aliquots, at every unique combination of three pH values (6, 8, 10), four concentration factors (1X, 10X, 100X, 1000X), and three mixing times (1h, 4h, 24h). No statistically significant (p < 0.05) differences in TOC concentration were observed with respect to pH, mixing time, or concentration factor. However, TOC recovery was higher in reconstitutions at pH 10 than at pH 8, albeit at slightly less than 95% confidence (p = 0.086). The overall average TOC recovery was 101% (± 3.3%). Recovery of UV254 absorbance was significantly better at pH 10 than at pH 8 or 6. Mixing time did not significantly affect UV254 absorbance recovery. No statistically significant differences in UV254 were observed between reconstitutions at 1X, 10X, and 100X. A small but significant drop (4.85%, p = 0.029) in UV254 recovery was observed between 100X and 1000X samples.