Evaluating Dissolved Organic Matter with GPC and Spectroscopy

In a joint study by the Beijing University of Civil Engineering and Architecture (China) and the China Construction Fifth Engineering Division (Changsha, China), water treatment facility sludge was employed as filler in a filter system to evaluate its ability to remove dissolved organic matter (DOM) from road runoff. The researchers used analytical techniques such as gel permeation chromatography (GPC), ultraviolet-visible (UV–vis) spectroscopy, and excitation-emission matrix (EEM) fluorescence spectroscopy in their evaluation. This analysis was performed to determine the primary removal components of DOM. A paper based on this study was published by Water Science & Technology (1).

The term DOM encompasses a category of organic mixtures that are characterized by a broad range of molecular weights, complex composition and structure, and physical heterogeneity (2). Commonly found in natural and human-impacted waters, such as surface water and wastewater (3), DOM influences the formation and dissolution of minerals, the stability of the colloidal state, the cycling of trace metals, and the migration of organic and inorganic pollutants (4). DOM can react with disinfectants, including chlorine-based ones, during drinking water preparation, and producing large amounts of highly toxic disinfection by-products such as polychlorinated biphenyls (PCBs), trihalomethanes (THMs), and other substances with carcinogenic, mutagenic, and teratogenic effects can be produced (5,6).

The authors report that the sludge-filled filter displayed superior performance in the elimination of runoff DOM, achieving a removal rate of 70–80% throughout the entire rainfall event. This filter targeted macromolecular DOM components, hydrophobic organic compounds, as well as acidic and neutral organic substances from road runoff, effectively. Fluorescence spectrum analysis indicated that the sludge from drinking water treatment plants could efficiently adsorb fulvic acid-like and humic acid-like substances present in runoff DOM. In addition, it expedited the multiplying of microorganisms, enhancing the degradation of protein-like substances. Filtration resulted in decreased aromatization and humification in runoff DOM as well, through the removal of aromatic compounds and macromolecular substances. The degree of humification and molecular weight of DOM in the effluent notably decreased markedly in the sludge-filled filter because of effective removal processes applied to aromatic compounds and macromolecular substances from road runoff (1).

While the authors believe that their findings highlight the potential of sludge-based filters as a sustainable and effective solution for urban runoff treatment, especially in areas with high traffic pollution, they also state that further research is needed to evaluate long-term performance of these filters, including potential clogging or adsorption saturation challenges and their impact on microbial ecosystems. Pilot studies in urban areas where traffic is more intensive and/or climate conditions are different were recommended to optimize the applicability of the technology. The integration of sludge-based filters into comprehensive urban water management systems alongside existing treatment methods could also enhance treatment efficiency of treatment, as well as protect downstream aquatic environments (1).

Sewer hatch during a rain flood. © Martin Bergsma - stock.adobe.com

References

1. Du, X.; Jing, W.; Jiang, R.; Chen, M.; Liu, D. Removal of Dissolved Organic Matter in Road Runoff with Sludge-Based Filters from the Drinking Water Treatment Plant. Water Sci. Technol. 2025, 91 (2), 160-173. DOI: 10.2166/wst.2024.405

2. Wegley Kelly, L.; Nelson, C .E.; Petras, D.; Koester, I.; Quinlan, Z. A.; Arts, M. G. I.; Nothias, L. F.; Comstock, J.; White, B. M.; Hopmans, E. C.; van Duyl, F. C.; Carlson, C. A.; Aluwihare, L. I.; Dorrestein, P. C.; Haas, A. F. Distinguishing the Molecular Diversity, Nutrient Content, and Energetic Potential of Exometabolomes Produced by Macroalgae and Reef-Building Corals. Proc. Natl. Acad. Sci. U S A 2022, 119 (5), e2110283119. DOI: 10.1073/pnas.2110283119

3. Chen, M.; Xu, J.; Tang, R.; Yuan, S.; Min, Y.; Xu, Q,; Shi, P. Roles of Microplastic-Derived Dissolved Organic Matter on the Photodegradation of Organic Micropollutants. J. Hazard. Mater. 2022, 440, 129784. DOI: 10.1016/j.jhazmat.2022.129784

4. Pan, Y.; Garg, S.; Ouyang, Y.; Yang, X.; Waite, T. D. Inhibition of Photosensitized Degradation of Organic Contaminants by Copper Under Conditions Typical of Estuarine and Coastal Waters. J. Hazard. Mater. 2023, 458, 131812. DOI: 10.1016/j.jhazmat.2023.131812

5. Garrido Reyes, T. I.; Mendoza Crisosto, J. E.; Varela Echeverria, P. S.; Mejías Barrios, E. G.; Álvarez Salgado, X. A. Interaction Between Polychlorinated Biphenyls and Dissolved Organic Matter of Different Molecular Weights from Natural and Anthropic Sources. J. Environ. Manage. 2021, 299, 113645. DOI: 10.1016/j.jenvman.2021.113645

6. Wang, X.; Tong, Y.; Chang, Q.; Lu, J.; Ma, T.; Zhou, F.; Li, J. Source Identification and Characteristics of Dissolved Organic Matter and Disinfection By-Product Formation Potential Using EEM-PARAFAC in the Manas River, China. RSC Adv. 2021, 11 (46), 28476-28487. DOI: 10.1039/d1ra03498g