A Simplified DOC Fractionation SPE Method Without Recovering Sorbed Compounds

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 specific THM formation potential (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 role of specific DOC fractions in THM formation.本研究旨在深化对水处理过程中溶解性有机碳（dissolved organic carbon, DOC）组分的认识。当前主流的分馏方法如固相萃取（Solid Phase Extraction, SPE）主要聚焦于回收吸附态化合物，并默认水处理过程仅影响DOC组分的总量，而非其特性。此外，回收率的差异以及分馏pH定义的不统一，使得亲水组分（hydrophilic, HPI）与疏水组分（hydrophobic, HPO）的DOC组成在不同研究间难以横向比较。针对这些不足，本研究探讨了不同pH调控方式（pH 3、pH 7及顺序调节）对针对固相萃取滤液中有机化合物的DOC分馏的影响，同时分析了混凝、软化及过滤工艺对DOC组成与特性的作用。 本研究提出了一种新型分馏方法：采用Bond Elut ENV固相萃取柱，在pH 3与pH 7两个条件下，对主要DOC组分进行定量，包括亲水中性组分（hydrophilic neutral, HPIN）、总酸性组分（total acidic, TA）与疏水中性组分（hydrophobic neutral, HPON）。该方法无需回收吸附态DOC组分，简化了实验流程，同时提升了不同研究间横向比较的一致性。在某常规混凝/软化水厂的应用结果显示，处理后HPON占比下降，而HPI与TA的相对占比上升。但经处理后的水中HPI组分表现出显著更高的比三卤甲烷生成势（specific THM formation potential, STHMFP），且其低分子量化合物占比约为原水HPI的两倍，这表明水处理过程后DOC组分在含量与特性两方面均发生了显著变化。本研究结果表明，在处理后水体中，HPI DOC组分对紫外吸光度比（SUVA）与三卤甲烷生成势（THM formation potential, THMFP）的贡献高于HPO DOC组分。 本研究采集的数据涵盖不同水样的DOC浓度、紫外254吸光度、THMFP，以及采用高效体积排阻色谱（high-performance size exclusion chromatography, HPSEC）测得的分子量分布，同时包含不同分馏pH条件下及不同SPE类型（Bond Elut C18、C18-EWP与ENV）的固相萃取滤液相关数据。此外，本研究针对饮用水应用中采用大体积树脂或SPE方法分离得到的DOC组分开展了全面的文献综述。该数据集全面展现了常规水处理过程中DOC的行为特征，可帮助水处理从业者通过考量整个处理流程中DOC组成的变化，设计更高效的工艺；研究人员则可借助这些发现，更好地理解基于pH的分馏方法、DOC芳香性，以及特定DOC组分在THM生成过程中的作用。