Response of VFAs Produced by Kitchen Waste Fermentation to Intermittent pH Regulation and Enhanced Denitrification Efficiency

To investigate the effects of intermittent pH regulation on volatile fatty acid (VFA) production during kitchen waste fermentation and its impact on nitrogen removal efficiency in the anaerobic/anoxic/oxic (A2O) process, five experimental groups were set up (pH = 3, 5, 7, 9, and control). The study examined the promotion of soluble chemical oxygen demand (SCOD) and VFA release under different pH conditions and their contribution to total nitrogen (TN) release. Additionally, methanol was used as a control carbon source to explore the enhancement of denitrification efficiency when kitchen waste fermentation broth was used as a carbon source in the A2O process. The results indicated that neutral and alkaline conditions could enhance the release of SCOD and the conversion of VFAs, with a more pronounced effect under alkaline conditions. The maximum concentrations of SCOD and VFAs reached 36,412 and 5947 mg/L, respectively. Furthermore, TN release was most significant under alkaline conditions, being 2.39 times that of the control group. When kitchen waste fermentation broth was used as a carbon source, Proteobacteria and Bacteroidota were significantly enriched. Additionally, the relative abundance of key functional genes (napA, norB, and nosZ) involved in nitrogen cycling and key enzymes ([EC: 1.7.1.15], [EC: 1.7.2.1], and [EC: 1.7.2.5]) were enhanced, which strengthened the denitrification performance.