Pre-treatment of alcohol precipitation wastewater of Chinese patent medicine by anaerobic digestion and microbial community changes during the pre-treatment process

ABSTRACT The alcohol precipitation wastewater produced during the manufacture of Chinese patent medicine (CPM) was investigated in an anaerobic digestion process as a biological pre-treatment method. After a 220-day debugging period, the anaerobic digestion process reached stability with an excellent chemical oxygen demand (COD) removal rate (>85%) were achieved and the influent's COD, ammonium (NH4+-N), and total nitrogen (TN) concentrations were 21,000, 200, and 400 mg/L, respectively. The microbial degradation mechanisms were analyzed by 3D fluorescence and UV–Vis, which revealed that humic acids (e.g., alkanes) were predominant among the soluble organics, leading to diminished bio-toxicity and aromaticity. The results of 16S rRNA high-throughput sequencing showed that Methanothrix, Methanobacterium, Bacteroides, and Sphaerochaeta were dominant phyla in the anaerobic digestion reactor, collectively accounting for 21.88% of the relative abundance. Additionally, certain bacteria potentially engaged in the degradation of aromatic compounds, nitrification, denitrification, and anaerobic ammonium oxidation, including Rhodococcus, Hyphomicrobium, and Candidatus_Kuenenia, constituted 3.96% of the total abundance. Effective and efficient elimination of macromolecular organics confirmed that the anaerobic digestion process was feasible for pre-treatment of CPM wastewater.