Exploring 2,4,6-Trichlorophenol Degradation Characteristics and Functional Metabolic Gene Abundance Using Sludge Fermentation Broth as the Carbon Source

Abstract

The use of sludge fermentation broth (FB) as a co-metabolic carbon source for treating 2,4,6-trichlorophenol (2,4,6-TCP) wastewater is a novel strategy. The key to the feasibility of this strategy is whether the FB can promote the growth of functional microorganisms that are capable of degrading 2,4,6-TCP. This study focused on long-term acclimatized sludge and investigated the impact of key operating parameters such as the sludge FB concentration and the influent concentration of 2,4,6-TCP on the removal efficiency of chlorophenol. The research findings revealed that when the influent concentration of sludge FB exceeded 300 mg COD/L, it significantly inhibited the degradation of 2,4,6-TCP. Simulation experiments using individual VFA components as influent carbon sources showed that excessive propionic acid addition can inhibit the degradation of 2,4,6-TCP, indicating the need to control the concentration of propionic acid in the fermentation conditions. Metagenomic analysis further showed that sludge FB can promote the enrichment of microbial chlorophenol degradation genes, including PcpA, pcaF, pcaI, Mal-r, chqB, and fadA. The abundances of these six chlorophenol degradation genes were as follows: 1152 hits (PcpA), 112 hits (pcaF), 10,144 hits (pcaI), 12,552 hits (Mal-r), 8022 hits (chqB), and 20,122 hits (fadA). Compared with other types of carbon sources, sludge FB demonstrates distinct advantages in terms of leading to the highest chlorophenol degradation concentration and the abundance of functional microbial communities. This study has successfully demonstrated the feasibility of using sludge FB as a co-metabolic carbon source for the degradation of 2,4,6-TCP.