Nitrate is a common co-contaminant with 2,4-dichlorophenol (2,4-DCP) in water, presenting a challenge for environmental remediation. Under anaerobic conditions, the ring cleavage of chlorophenol is inefficient, while under aerobic conditions, nitrate removal is hindered. In this study, a microbial consortium capable of hydrogenotrophic denitrification and 2,4-DCP degradation was cultured, aiming to achieve efficient nitrate removal and 2,4-DCP degradation by alternately switching between hydrogen (H2) and oxygen (O2). Under H2 conditions, nitrate removal exceeded 90 %, while under O2 conditions, 2,4-DCP degradation reached 100 %. Under H2 conditions, the abundance of the Nar gene which was involved in nitrate reduction was higher than that under O2 conditions, promoting hydrogenotrophic denitrification. In contrast, under O2 conditions, 2,4-DCP degradation occurred via hydroxylation, ring-cleavage, dechlorination, and mineralization through the TCA cycle. Metagenomic and metabolomic analysis was performed to explore microbial metabolic pathways and potential synergistic mechanisms involved in hydrogenotrophic denitrification and 2,4-DCP biodegradation. In the H2-atmosphere, microbes (Methylobacillus and Chromobacterium), genes (E3.1.1.45 and speG), and metabolites (Cytosine and Uridine) may play a crucial role in hydrogenotrophic denitrification. In the O2-atmosphere, the functional genus of Paracoccus and Aquamicrobium associated with genes (tfdB and tfdC) may contribute to 2,4-DCP and its metabolites 2-Chloromaleylacetate degradation. These findings confirmed the role of functional microbial communities through H2/O2 regulation. This work provides a promising technological reference for treating industrial wastewater containing phenols and nitrogen.