Dissolved organic matter removal

Tan Y., Kilduff J.E. Factors affecting selectivity during dissolved organic matter removal by anion-exchange resins. Water Research 2007 41(18) 4211-4221. 

Hayase et al. [684] first extracted the seawater sample with chloroform to remove dissolved organic matter prior to analysis of the aqueous phase by graphite furnace atomic absorption spectrometry. Seawater samples at pH 3 and at pH 8 were extracted with chloroform, evaporated to dryness, and the residue treated with nitric acid. Acid solutions were subjected to metal analyses by graphite furnace atomic absorption spectrometry. 

Another method of segregating and removing a portion of the dissolved organic matter includes incorporation into a solid phase, which can then be removed by filtration or centrifugation. This incorporation can result either from coprecipitation with a solid phase formed in a reaction in the solution or, as discussed in the next section, from adsorption of the organic material onto a pre-existing solid phase. 

Once a sample of dissolved organic matter has been isolated, it is still seldom in a form that permits simple analysis. In most cases, there are far too many compounds present and some form of fractionation must take place to remove interferences and simplify analytical procedures. 

A soil sample is placed in a centrifuge tube, mixed with 0.5 M HC1 for 1 hour, and centrifuged. The HC1 solution is removed and the soil washed with water to remove the acid. The soil is then extracted with 0.5 M NaOH for 18 hours with shaking, followed by centrifuging to remove dissolved organic matter from soil (adapted and condensed from Reference 21). 

When released to surface waters, mirex will bind primarily (80-90%) to the dissolved organic matter in the water with a small amount (10-20%) remaining in the dissolved fraction, because mirex is a highly hydrophobic compound (Yin and Hassett 1989). Mean mirex concentrations in sediments, collected at four basins in Lake Ontario between 1982 and 1986, ranged from 30 to 38 pg/kg in three of the basins within the water circulation pattern of the lake. A fourth basin outside the pattern showed much lower concentrations (6.4 pg/kg), indicating that mirex was being transported with the lake water (Oliver et al. 1989). The residence time for mirex in Lake Ontario water was estimated to be 0.3 years. This indicated that mirex was either scavenged by particles or was chemically reactive and, therefore, was rapidly removed from the water column (Arimoto 1989). 

The relative improvements (reference is particle removal without ozone) are quite variable, but were reported to be about 20-90 % lower turbidities and/or lower particle counts in the filtered water. The presence of dissolved organic matter is frequently essential and DOC should be at least 1 mg L The preozonation effects depend strongly on the presence of alkaline earth cations, especially calcium. 

Vermilion, B.R. and RJ.M. Hudson. 2007. Thiourea catalysis of MeHg hgand exchange between natural dissolved organic matter and a thiol-functionalized resin A novel method of matrix removal and MeHg preconcentration for ultratrace Hg speciation analysis in freshwaters. Anal. Bioanal. Chem. 388 341-352. 

Carlson, C. A. (2002). Production and removal processes. In Biogeochemistry of marine dissolved organic matter (HanseU, Carlson, eds.). Academic Press, San Diego, CA, pp. 91—151. 

In a recent review of technological alternatives for NOM removal, Jacangelo et al. [558] presented field data that illustrate wide variability in adsorption capacities of activated carbon in a single location (e.g., exhaustion periods between 41 and 182 days). They concluded that these results are evidence of the site-specific nature of [dissolved organic carbon] removal by [activated carbon] and that the concerns regarding reliability of treatment practices to meet the new [regulations] have a sound basis. Clearly, much fundamental work remains to be done to understand fully the complex nature of these adsorbent/adsorbate interactions and thus be able to optimize both the physical and the chemical accessibility of the carbon surface to natural organic matter. 

In the Battelle Northwest study (15,17), raw sewage was contacted with PAC to effectively remove the dissolved organic matter. An inorganic coagulant (alum) was then used to aid in subsequent clarification. Polyelectrolytes were added, followed by... 

Activated carbon has been used in water and wastewater treatment facilities and industries for dechlorination (9). Free as well as combined chlorine from water can be removed by activated carbon. In water treatment plants carbon filters effectively remove dissolved organic matter in addition to removing chlorine. 

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