Coupling reverse osmosis with electrodialysis to isolate natural organic matter from fresh waters.

Reverse osmosis (RO) has proven to be an effective method for the concentration of natural organic matter (NOM) from fresh waters, but an undesirable consequence of this process is the co-concentration of some inorganic solutes. Accordingly, current practice yields solutions of NOM that, upon desalting and freeze-drying, are converted into dry solids containing finely dispersed sulfuric acid and silicic acid (H(4)SiO(4)). These acids will contribute to the apparent carboxylic and phenolic contents of NOM, leading to an overestimation of both. NOM may also be chemically altered by sulfuric acid, which reacts strongly with many classes of organic compounds. The sulfur content and ash content of NOM will be elevated in the presence of sulfuric acid and H(4)SiO(4). The goal of this study is to develop and test a method in which the removal of water by RO is coupled with the removal of salts by electrodialysis (ED). Like RO, ED is a relatively mild treatment that enables the desalting of NOM solutions without subjecting those samples to conditions of extremely high or low pH. The end product of the coupled process is a desalted, concentrated liquid sample from which low-ash NOM can be obtained as a freeze-dried solid material. In this study, the efficacy of ED for desalting NOM is evaluated using concentrated synthetic river waters and actual concentrated (by RO) river waters. Under optimal operating conditions, both sulfate and silica can be largely removed from RO-concentrated solutions of riverine NOM with only an average loss of 3% of total organic carbon.

[1]  J. Allison,et al.  MINTEQA2/PRODEFA2, a geochemical assessment model for environmental systems: Version 3. 0 user's manual , 1991 .

[2]  K. Mopper.  Sugars and uronic acids in sediment and water from the black sea and north sea with emphasis on analytical techniques , 1977 .

[3]  R. Baker.  Membrane Technology and Applications , 1999 .

[4]  Hong-Joo Lee,et al.  Characterization of anion exchange membranes with natural organic matter (NOM) during electrodialysis , 2003 .

[5]  M. Kitis,et al.  Isolation of dissolved organic matter (DOM) from surface waters using reverse osmosis and its impact on the reactivity of DOM to formation and speciation of disinfection by-products. , 2001, Water research.

[6]  J. Meyer,et al.  Use of elemental composition to predict bioavailability of dissolved organic matter in a Georgia river , 1997 .

[7]  C. Keller,et al.  A non-adsorptive method for the isolation and fractionation of natural dissolved organic carbon , 1996 .

[8]  Colin R. Janssen,et al.  Reverse osmosis sampling does not affect the protective effect of dissolved organic matter on copper and zinc toxicity to freshwater organisms. , 2005, Chemosphere.

[9]  Jaeweon Cho,et al.  Investigation of the adsorption and transport of natural organic matter (NOM) in ion-exchange membranes , 2003 .

[10]  E. Perdue,et al.  Isolation of dissolved organic matter from the suwannee river using reverse osmosis , 1990 .

[11]  P. Maurice,et al.  A comparison of surface water natural organic matter in raw filtered water samples, XAD, and reverse osmosis isolates. , 2002, Water research.

[12]  J. McCarthy,et al.  Using reverse osmosis to obtain organic matter from surface and ground waters , 1995 .

[13]  E. Korngold,et al.  6 – Electrodialysis—Membranes and Mass Transport , 1984 .

[14]  Georges Belfort.  Synthetic membrane processes : fundamentals and water applications , 1984 .

[15]  L. McGown,et al.  Multi-method characterisation of natural organic matter isolated from water: characterisation of reverse osmosis-isolates from water of two semi-identical dystrophic lakes basins in Norway , 1998 .

[16]  E. Perdue,et al.  Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter , 2003 .

[17]  M. Kitis,et al.  Effects of reverse osmosis isolation on reactivity of naturally occurring dissolved organic matter in physicochemical processes. , 2004, Water research.

[18]  Robert A. Berner,et al.  Global Environment: Water, Air, and Geochemical Cycles , 1995 .