No abstract

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the sludge environment due to activities such as oil extraction and pose a serious threat to deep-seated anaerobic microorganisms. Thus, in this study, we discussed the dose–response efficiency of naphthalene (Nap, a typical PAH) on anaerobic digestion (AD) through co-metabolic degradation via batch experiments. The batch results showed that 30 mg/L Nap promoted the AD with the accumulation of CH4 18.54% higher than the control (without Nap) by increasing the efficiency of hydrolysis and acetogenesis 99.49% and 61.95%, respectively. However, adverse effects were observed with an excessive dosage of Nap (higher than 100 mg/L) with a decrease of methane production (37.16) with 2000 mg/L Nap. Interestingly, the concentrations of the polysaccharide and protein reached the highest at 138.76 mg/L and 400.41 mg/L, respectively, in 1000 mg/L Nap. Furthermore, the high activities of hydrolase and transmembrane ATPase were acquired in 30 mg/L Nap. In addition, Nap significantly affected the methanogenic microbial abundance and diversity, especially diminishing Methanolinea and Syntrophobacter. Furthermore, the enrichment of Bacteroides in 30 mg/L Nap showed moderate Nap could facilitate hydrolysis. The genes relevant to cellular processes were activated by Nap. This research provided a reliable basis for the anaerobic microbial response under Nap stress.