Algal organic matter impact on 2-methylisopropanol and geosmin adsorption by activated carbon: Variation with algae growth and decay, prediction by fluorescence surrogates

Abstract

Algae-producing odorants have negative effects on the aesthetic quality of drinking water, and activated carbon adsorption is commonly used to abate the odorants. However, in eutrophic waters, algal organic matter (AOM) produced by the dominant cyanobacteria (e.g., Microcystis aeruginosa) strongly interferes with the activated carbon adsorption of trace odorants from source waters. In this study, the applicability of using spectrometric surrogates to evaluate the effect of AOM from Microcystis aeruginosa on odorant adsorption by activated carbon was investigated. During the stationary phase, the DOC concentration of extracellular organic matter (EOM) increased due to algal metabolism (from 3.52 mg/L to 7.81 mg/L) and further accumulated (to 12.40 mg/L) during the decline phase due to the release of intracellular organic matter (IOM), resulting in increased competition against odorants. The adsorption of chromogenic organics in AOM was first evaluated to screen possible spectrometric surrogates for predicting odorant adsorption. The fluorescence component (Ex: 260 nm/Em: 400–460 nm) was the best candidate for predicting odorant adsorption in both AOM solutions and reservoir water. In contrast, poor performance was found for the commonly used UV absorbance at 254 nm and protein-like fluorescence components, due to the weak adsorbability of corresponding chromogenic materials. Our results indicate that fluorescence spectroscopy is promising in predicting odorant adsorption with AOM interference in source waters.