A Simplified DOC Fractionation SPE Method Without Recovering Sorbed Compounds

Description

This research aims to advance the understanding of dissolved organic carbon (DOC) fractions in water treatment processes. Current fractionation methods, such as Solid Phase Extraction (SPE), primarily focus on recovering sorbed compounds and assume that treatment impacts only the quantity, not the characteristics, of DOC fractions. Additionally, varying recovery rates and inconsistent fractionation pH definitions complicate cross-study comparisons of hydrophilic (HPI) and hydrophobic (HPO) DOC composition. This study addresses these gaps by investigating the impact of different pH approaches (pH 3, pH 7, and sequential adjustment) on DOC fractionation focused on organic compounds in the SPE filtrate, as well as the effects of coagulation, softening, and filtration on DOC composition and characteristics. We introduced a novel fractionation method using Bond Elut ENV cartridges at two pH levels—pH 3 and pH 7—to estimate major DOC fractions: hydrophilic neutral (HPIN), total acidic (TA), and hydrophobic neutral (HPON). This approach eliminates the need to recover sorbed DOC fractions, simplifying the process and enabling more consistent cross-study comparisons. Applying this method in a conventional coagulation/softening plant revealed HPON decreased while the relative amounts of HPI and TA increased after the treatment. However, the treated water HPI exhibited significantly higher STHMFP and contained approximately twice the proportion of low-molecular-weight compounds than raw water HPI, highlighting significant changes in both the content and properties of DOC fractions after the treatment process. Our study indicates the contribution of HPI DOC fraction to SUVA and THM formation potential (THMFP) in treated water is greater than that of HPO DOC. The data collected, including DOC concentrations, UV254 absorbance, THMFP, and molecular weight distribution using high-performance size exclusion chromatography (HPSEC) across different water samples and in SPE filtrates at various fractionation pH values and SPE types (Bond Elit C18, C18-EWP, and ENV). Also, we conducted a thorough literature review on DOC fractions isolated using bulk resin or SPE methods in drinking water applications. The data provides a comprehensive view of DOC behavior in conventional water treatment processes. This dataset can help practitioners design more efficient processes by considering changes in DOC composition throughout treatment. Researchers can apply these findings to understand better the influence of pH-based fractionation, DOC aromaticity, and the roles of specific DOC fractions in THM formation.

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