Abstract
Nitrates are widely present in aquatic ecosystems, posing a threat to the environment and human health. Heterotrophic denitrification using plant-based biomaterials has emerged as an effective method for removing nitrates from contaminated waters. This study investigates the mechanisms and influencing factors of heterotrophic denitrification, using acorn cups as a plant-derived solid organic carbon source for denitrifying bacteria. The results highlight the distinctive characteristics of acorn cups, their effectiveness in supporting bacterial denitrification, and their notable physical stability. The results of analyses conducted using Fourier-transform infrared spectroscopy, atomic absorption spectroscopy, and X-ray fluorescence revealed a high carbon content and the presence of trace elements, which provide essential nutrients for denitrifying bacteria. In addition, scanning electron microscopy revealed a highly porous structure that enhances microbial adhesion. This low-cost, underutilised biomaterial often considered a by-product demonstrated strong denitrification efficiency, achieving a nitrate removal rate of 95.38 ± 0.13 % at neutral pH and up to 99.72 ± 0.17 % under high biomass conditions. Based on these results, it can be concluded that acorn cups represent a technically, economically, and environmentally promising solution for biological denitrification.