Exploring the effect of dissolved organic matter on trimethoprim adsorption by activated sludge at environmentally relevant concentration

BACKGROUND Dissolved organic matter (DOM) in wastewater treatment systems plays a crucial role in the adsorption removal of antibiotics; however, this adsorption process remains underexplored. In this study, the effect of DOM components (protein, humic substances and polysaccharide) on the adsorption removal of trimethoprim (TMP) by activated sludge at environmentally relevant concentrations was investigated. RESULTS The humic substance had a positive effect on TMP adsorption, whose adsorption capacity was increased from 6.05 to 10.82 and 7.48 μg g −1 volatile suspended solids ( P < 0.05), respectively, when 60 mg L −1 humic acid and fulvic acid were added. The negatively charged protein (30 mg L −1 ) had an inhibition effect on TMP adsorption process, in which the adsorption capacity was reduced by 24.1% ( P < 0.05). However, the positively charged protein had a minor promotional effect. The polysaccharides (10 mg L −1 ) had a negligible effect on TMP adsorption. CONCLUSION Through infrared and X-ray photoelectron spectroscopy analysis, the hydrogen bond was found to be the main factor governing TMP adsorption by activated sludge with DOM interference. © 2025 Society of Chemical Industry (SCI).