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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]

[Display omitted] • Microbial electrolysis cell was integrated in different phases of different TPAD. • Thermophilic conditions enhanced hydrolysis more than microbial electrolysis cell. • TPAD integrated microbial electrolysis cell improved the methane yield. • Microbial electrolysis cell was more effective in mesophilic-mesophilic TPAD. Temperature-phased anaerobic digestion (TPAD) and microbial electrolysis cell (MEC) are both able to improve hydrolysis and methane yield during anaerobic digestion (AD) of dewatered sludge. However, the effect of TPAD and MEC integration at different temperatures and different phases is unclear. This study investigated the effect of the integration of intermittent energization MEC in different phases of TPAD on the digestion of dewatered sludge. Thermophilic and MEC hydrolysis could release higher total ammonia nitrogen of 186.0% and 10.3% than control, mesophilic methanogenesis phase integrated with MEC relieved the ammonia inhibition and accelerated the acid utilization leading to the relief of acid accumulation. The ultimate methane yield of the TPAD integrated with MEC was increased by 118.9%, in which the relative abundance of Methanothermobacteria and Methanosarcina was increased. Therefore, intermittent energization MEC integrated TPAD synchronously improved the hydrolysis and methane yield. [ABSTRACT FROM AUTHOR]

Highlights: [•] Protein degradation mainly limited by hydrolysis under aerobic condition. [•] Protein degradation limited by hydrolysis and metabolism under anaerobic condition. [•] Humification degree of aerobic digested sludge was greater than anaerobic one. [ABSTRACT FROM AUTHOR]

The gradual increase in cattle farming has led to a huge production of cattle manure (CM), but the conventional treatment methods are less efficient. In this study, the treatment method of anaerobic digestion (AD) of high-solids CM by combining nanobubble water (NBW) with different gases was proposed to present a new idea for the reduction, harmlessness, and resourcefulness of CM. It was found that the performance of the digester with added NBW was better than the control. Among them, the cumulative methane yield T-Air: 227.09 mL g−1 VS added and T-CO 2 : 226.12 mL g−1 VS added increased by 17.72 % and 17.22 %, respectively, compared with the control T: 192.90 mL g−1 VS added under thermophilic conditions. Under mesophilic conditions, M-Air: 162.39 mL g−1 VS added increased by 9.68 % compared with control M: 148.05 mL g−1 VS added. Microbial communities analyzed at the genus level revealed that the relative abundance of bacteria favorable to hydrolysis and acid-producing processes, such as Defluviitalea , Haloplasma , and Bacillus , increased to varying degrees. Moreover, the relative abundance of archaea favorable for methanogenesis, such as Methanoculleus , Methanobrevibacter , and Methanosarcina , also increased to varying degrees. Therefore, the addition of NBW promoted the hydrolysis of high-solids CM, enhanced the stability of the reaction, improved the methanogenic performance, and increased the RA of favorable genera, which ultimately led to a better performance of the AD of high-solids CM. [Display omitted] • Compared with control, NBW increased CH 4 production by 5–17 %. • Compared with control, NBW contributes to the production/transformation of VFAs. • Incorporation of NBW improves stability of high solids anaerobic digestion. • Compared with control, NBW increased the RA of hydrolytic acidification-associated bacteria. • Compared with control, NBW increased the RA of methanogenic-associated archaea. [ABSTRACT FROM AUTHOR]