In situ ultrasonic-backwash regeneration of upflow activated carbon filters for improved removal of organics from drinking water

In this study, in situ ultrasonic-backwash regeneration of upflow activated carbon filters for enhanced removal of organic matter from drinking water was investigated by treating granular activated carbon at different ultrasonication frequencies (40 and 120 kHz). The activated carbon was physically characterized before and after treatment by SEM, BET, FTIR, XPS, and XRD, and the microbial diversity of the biofilm on the regenerated activated carbon was also analyzed. The results of 120-day tracking analysis showed that ultrasonic-backwashing regeneration improves the organic-matter-removal efficiency by 5 %–13 %, with the regeneration effect of ultrasonic waves at 120 kHz being superior to that at 40 kHz. Characterization of the activated carbon showed that ultrasonic treatment increases its mesopore content while decreasing its particle size but does not change its elemental composition or crystal structure, although prolonged high-frequency sonication appears to decrease the number of oxygen-containing functional groups on the carbon surface, which may benefit wettability. Furthermore, the treatment does not change the core species of the microbial community on the activated carbon. Overall, the treatment is a cost-effective and efficient way to improve the removal of organic matter from drinking water.