Effectiveness of low-intensity ultrasound on anaerobic bioaugmentation of phenolic wastewater: Model optimization and system stabilization

The study optimized the parameters of low-intensity ultrasound (LIUS), including ultrasound density (0.25 W·mL−1), duration (12 min), and interval time (48 h), through a combination of uniform experiments and response surface prediction. The optimized parameters were aimed at enhancing the removal efficiency of phenolic wastewater to approximately 80%. Furthermore, they facilitate the production of hydrolytic gases in anaerobic digestion, resulting in methane accumulation of up to 237.3 mL·(g VS)−1. Following the long-term experiment, LIUS has been demonstrated to effectively enhance the enzyme activity of anaerobic organisms while also damaging the bacterial structure of microorganisms. However, microbiological analysis indicates that the ultrasound-induced screening mechanism effectively increases the relative abundance of dominant bacterial communities. This facilitated the removal of persistent phenolic contaminants and stabilized the balanced development of the overall anaerobic environment. These findings suggest that LIUS can enhance biological activity and improve the anaerobic treatment of phenolic wastewater.