Geosmin adsorption

Even if fish populations could be maintained by aeration, biocides may not be effective in controlling off-flavors. Most of the geosmin present (ca. 90-99%) is associated with cells rather than the media (16,43, 60,12), Biocide induced cell lysis may release off-flavor metabolites from cells (67) and render them available for adsorption by fish (8,9,13), Off-flavor metabolites require long periods of time to clear from fish (57). Off-flavor-producing populations may become reestablished before off-flavor metabolite clearance is complete. In addition, the biocides used may be carried off-site or taken up by fish. 

The removal of MIB and geosmin from potable water has been the focus of many studies. Most studies have shown large differences between activated carbons [66]. Figure 26.1 indicates that the volume of pores on the range <0.1 nm is the controlling factor in the adsorption of MIB, although some research has shown surface chemistry also plays a role [8, 67]. 

The practical application of PAC for the removal of MIB and geosmin has been aided by the application of the HSDM [63, 64, 68]. Figure 26.8 illustrates the difference in the adsorption of the two compounds, and the fit that the HSDM can give to the data. Diffusion coefficients derived from these fits can then be used to predict the adsorption of the taste and odor compounds, and consequently the PAC doses required under particular water treatment plant situations [63, 68, 69]. 

The adsorption of microcystins has been shown to be strongly affected by NOM [78]. In this work the effect, for four microcystin variants, was shown to be a function of the DOC concentration. This is prohahly a result of the direct competitive effect, where the competitive NOM, those compounds approximately the same molecular weight as the microcystins, makes up the hulk of the NOM. Therefore the bulk characterization parameter, DOC, gives an indication of the concentration of competing compounds, where for MIB and geosmin it could not [27, 63, 69]. 

Matsui Y, Aizawa T et al (2007) Adsorptive removal of geosmin by ceramic membrane liltratimi with super-powdered activated carbon. J Water Supply Res Technol - AQUA 56 (6-7) 411 18... 

Ellis, J. and Korth, W. (1993) Removal of geosmin and methylisobomeol from drinking water by adsorption on ultrastable Zeolite-Y. Water Res. 27, 535-539... 

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