How β-Cyclodextrin-Functionalized Biochar Enhanced Biodenitrification in Low C/N Conditions via Regulating Substrate Metabolism and Electron Utilization

Abstract

Biodenitrification plays a vital role in the remediation of nitrogen-contaminated water. However, influent with a low C/N ratio limits the efficiency of denitrification and causes the accumulation/emission of noxious intermediates. In this study, β-cyclodextrin-functionalized biochar (BC@β-CD) was synthesized and applied to promote the denitrification performance of Paracoccus denitrificans when the C/N was only 4, accompanied by increased nitrate reduction efficiency and lower nitrite accumulation and nitrous oxide emission. Transcriptomic and enzymatic activity analyses showed BC@β-CD enhanced glucose degradation by promoting the activities of glycolysis (EMP), the pentose phosphate pathway (PPP), and the tricarboxylic acid (TCA) cycle. Notably, BC@β-CD drove a great generation of electron donors by stimulating the TCA cycle, causing a greater supply of substrate metabolism to denitrification. Meanwhile, the promotional effect of BC@β-CD on oxidative phosphorylation accelerates electron transfer and ATP synthesis. Moreover, the presence of BC@β-CD increased the intracellular iron level, causing further improved electron utilization in denitrification. BC@β-CD helped to remove metabolites and induced positive feedback on the metabolism of P. denitrificans. Collectively, these effects elevated the glucose utilization for supporting denitrification from 36.37% to 51.19%. This study reveals the great potential of BC@β-CD for enhancing denitrification under low C/N conditions and illustrates a potential application approach for β-CD in wastewater bioremediation.

Uncovering the Nonnegligible Mechanism of Degrading Structural Extracellular Polymeric Substances for Nitrate Removal in Psychrophilic (15 °C) Waste-Activated Sludge Fermentation

“…Especially, the unsatisfactory performance of nitrogen removal under low COD/TN conditions in WWTPs is deemed to be an obstacle in the application of denitrification. Extra carbon sources, such as acetate and propionate, are sometimes added, resulting in increased running costs. − Under such constraints, the waste-activated sludge (WAS) shall not be deemed as an unwanted organic byproduct . Anaerobic digestion (AD) is a biological method used to produce methane and volatile fatty acids (VFAs, including acetate and propionate). , However, low temperatures at high latitudes and high-altitude regions are often unfavorable for microbial growth, especially when they approach 0 °C. , It is estimated that energy consumption is equivalent to consuming 59% of the biogas produced in a mesophilic reactor and increases to 64% for a thermophilic reactor …”