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The operating temperature of anaerobic digesters should be adjusted to adapt to seasonal variations in environmental temperature and the composition of organic solid waste. This study investigated the effects of one-step abrupt temperature changes (from mesophilic to thermophilic temperature, M–T, and from thermophilic to mesophilic temperature, T–M) and the inoculation ratio on methane yield and microbial diversity during the anaerobic co-digestion of kitchen waste with dewatered sludge. The results showed that the cumulative methane yield (CMY) level resulting from thermophilic control and the M–T digesters was greater than that resulting from mesophilic control and the T–M digesters. The CMF of M–T digesters increased, whereas the CMY of T–M digesters gradually decreased with an increase in the inoculation ratio. The maximal CMY was 385.1 mL/g-VSSadded, which corresponded to an M–T digester with a 5% inoculation ratio. In the later stage of anaerobic digestion, the bacterial community of T–M was more diverse than that of M–T, but the archaeal community of M–T was more diverse than that of T–M. The one-step temperature change from thermophilic to mesophilic temperature was more stable than that from mesophilic to thermophilic temperature. [ABSTRACT FROM AUTHOR]

[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]