Humic acid as a model for natural organic matter (NOM) in the removal of odorants from water by cyclodextrin polyurethanes

Bb Mamba,Rw Krause,Sp Sithole,Tj Malefetse,Ti Nkambule

doi:10.4314/wsa.v35i1.76648

Abstract

Current practices in some water-treatment facilities have reported that natural organic matter (NOM) blocks the adsorption sites of activated carbon resulting in lower geosmin and 2-methylisoborneol (2-MIB) removal. Humic acid has been reported to compete with geosmin and 2-MIB removal in the same way. The removal of odour chemicals such as geosmin and 2-MIB is important for potable-water treatment by water supply companies and municipalities. We have previously demonstrated that cyclodextrin polyurethanes are capable of removing a number of organic pollutants from water, but are not able to reduce the levels of NOM significantly. We wished to determine if the polymers would selectively remove geosmin and 2-MIB, despite the presence of NOM. Humic acid was chosen as a model for NOM since NOM constitutes about 70% of humic acid. Results obtained from this study indicate that the presence of humic acids at different concentrations could not affect the removal of geosmin and 2-MIB when cyclodextrin polymers were used since 90% removal was achieved. However the UV-Vis analysis showed a low removal of humic acids (3 to 20%).

Highlights

Geosmin and 2-methylisoborneol (2-MIB) are organic compounds that cause bad taste and odour to drinking water
The effect of the presence of humic acid, on the adsorption of geosmin and 2-MIB was studied using synthetic water samples spiked with humic acid, geosmin and 2-MIB, which were treated with CD polymers
Treatment of the water samples spiked with humic acid, geosmin and 2-MIB showed that the polymers adsorbed up to less than LOQ, basically 90% based on Initial concentration Final concentration of humic acid of humic acid

Summary

Introduction

Geosmin and 2-methylisoborneol (2-MIB) are organic compounds that cause bad taste and odour to drinking water. Humic substances can be divided into three groups depending on the method of isolation from the original substance. These are fulvic acid, humic acid (HA) and humin. Humic substances adversely affect the quality of drinking water since they impart colour and serve as precursors for the formation of chlorinated compounds. They have complexing properties that include association with toxic elements and micro-pollutants (De Wuilloud et al, 2003)

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