Micropollutants, such as pharmaceuticals, personal care products or pesticides, are contaminants detected in levels from a few ng/L to several μg/L. For many of these contaminants, it is suspected that the trace concentration is sufficient to threaten the aquatic ecosystem and other exposed organisms including humans. The presence of micropollutants in water resources is currently a worldwide issue.<br/>Activated carbon (AC) adsorption is widely used for micropollutant removal in drinking water treatment plants (DWTPs). Although dissolved organic matter (DOM) may significantly influence the adsorption efficiency of micropollutants, our current capability is quite limited to quantitatively correlate the amount and characteristics of DOM with the adsorption efficiency. To deal with this challenge, it is necessary to understand the adsorptive behavior of micropollutants under the influence of different types of DOM. The aim of this study was to elucidate the correlations between the characteristics of DOM in DWTP source water and the removal of micropollutants by AC.<br/>Batch adsorption tests were conducted with five micropollutants, dimethoate, carbendazim, atrazine, metolachlor, and propiconazole, whose log Kow ranged from 0.78 to 3.72. Initial concentration of 1 μg/L each and AC dose of 2- 30 mg/L were used. Source water were collected from the inlet of two DWTPs (DWTP1, DWTP2) with dissolved organic carbon (DOC) concentration of 6.37 and 8 mg/L, respectively. At high AC dose of 20 mg/L or greater, all micropollutants showed very high removal efficiency (&gt;99%) regardless of the water source. For most target micropollutants, the decrease in the AC dose had greater impact on the removal efficiency for DWTP 1. This result was contrary to our expectation because DWTP 2 was higher in DOC and its DOM was more hydrophobic. DWTP 1 showed much greater specific UV absorbance at 254 nm value of 0.96 L/mg-m compared to that for DWTP 2 (0.34 L/mg-m).<br/>Our result strongly suggested that DOC concentration or DOM hydrophobicity is poorly correlated with competitive pressure of DOM for micropollutant adsorption. Further study is underway, which employs DOM characterization techniques such as fluorescence excitation emission matrix, to identify the DOM characteristics that best describe this competitive pressure and to develop a method that parameterizes the characteristics.

Influence of dissolved organic matter from different source water for drinking water treatment plants on the activated carbon removal of micropollutants

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ACS Fall 2022

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