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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: [•] Filler enhance conversion rates of sludge digestion. [•] Pre-incubated filler improve dewaterability of digested sludge. [•] Filler alone do not improve dewaterability of digested sludge. [Copyright &y& Elsevier]

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 sludge digestate stabilized by mesophilic anaerobic digestion was further degraded through thermophilic anaerobic digestion using 0-10 % (v/v) of thermophilic, proteolytic Coprothermobacter proteolyticus, and/or methanogenic granular sludge. The results demonstrated that the temperature shift to thermophilic condition promoted abiotic solubilization of proteins and reactivated the fermentative bacteria and methanogens indigenous in the sludge digestate, resulting in a final methane yield of 6.25 mmol-CH/g-volatile suspended solid (VSS) digestate. The addition of C. proteolyticus accelerated the hydrolysis and fermentation of proteins and polysaccharides in the digestate during the early stage of thermophilic anaerobic digestion and stimulated methane production by syntrophic cooperation with methanogenic granular sludge. In the treatment with granular sludge and inoculated with 10 % (v/v) of C. proteolyticus, a final methane yield of 7 mmol-CH/g-VSS digestate was obtained, and 48.4 % proteins and 27.0 % polysaccharides were degraded. The dissolved proteins were contributed by abiotic factor, C. proteolyticus, and indigenous digestate bacteria, respectively, by around 16, 28, and 56 %. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-digestion improved methane yield 31.3%-68.0% at thermophilic temperature. • Co-digestion improved methane yield 83.0%-136.5% at mesophilic temperature. • The highest methane yield of anaerobic co-digestion obtained at P/S = 2:1. • NCST and TS of sediment increased with increasing initial TS of substrate. • NCST has a strong negative correlation with the water removal efficiency. The objective of this study is to assess the effects of the mixing ratio on the methane production and digestate dewaterability of co-digestion of pig manure (P) and sludge (S). Batch experiments were carried out at five different P/S mixing ratios at mesophilic and thermophilic temperatures. Compared to sludge anaerobic digestion, co-digestion of pig manure with sludge increased methane yield 83.0%-136.5% at mesophilic temperature and 31.3%-68.0% at thermophilic temperature. The normalized capillary suction time (NCST) and total solids (TS) of sediment (centrifugal dewatering) increased when pig manure proportion of substrate increased. The NCST at thermophilic temperatures (4.87–17.58 s g−1-TSS) was higher than that at mesophilic temperatures (1.89–10.95 s g−1-TSS). However, the TS of sediment was close at thermophilic and mesophilic temperatures. The results indicated that anaerobic co-digestion of pig manure and sludge at a proper mixing ratio (P/S = 2:1) provides a good choice for energy recovery and land utilization. [ABSTRACT FROM AUTHOR]