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[Display omitted] • Four different NBWs were added to the sludge anaerobic digestion. • The hydrolysis of sludge anaerobic digestion can be enhanced by the addition of NBW. • Addition of NBW increased methane production by 9.0–27.8% compared with control. • Addition of NBW (Air, CO 2 , He, and N 2) improved the dewaterability of digestate. • Air-NBW was the most cost-effective additive for sludge anaerobic digestion. The subsequence anaerobic digestion (AD) of dewatered sludge (DWS) from wastewater treatment plants necessitates an emphasis on enhancing methane production and dewaterability. The effect of different nanobubble water (NBW) on AD of DWS was investigated under mesophilic conditions. Cumulative methane production was improved by 9.0–27.8% with the addition of different NBW (Air, CO 2 , He, and N 2). NBW improved methanogenic performance by significantly enhancing the hydrolysis of sludge AD. Results from the digestate, the capillary suction time, specific resistance to filtration, and moisture content could be decreased by 14.6–18.2%, 18.8–29.6%, and 13.6–19.5%, respectively. The addition of NBW can improve the dewaterability of digestate by reducing the digestate particle size and increasing the zeta potential of digestate. The addition of NBW significantly increased methane production and improved dewaterability in AD; Air-NBW showed the best improvement. [ABSTRACT FROM AUTHOR]