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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]

The role of total solids (TS) content on sludge mesophilic anaerobic digestion (AD) was investigated in batch reactors. A range of TS below 10% was evaluated with two replicates. The volumetric biogas production rate (VBPR) increased with increasing initial TS. On day 5, VBPR increased from 133.2 ± 11.2 mL L −1 d −1 at TS 2% to 1111.7 ± 58.1 mL L −1 d −1 at TS 10%. The ultimate biogas yield ( P ) firstly increased and then decreased with the increasing TS. The greatest P was 246.8 mL g −1 -VS added at TS 8%. The corresponding free ammonia nitrogen (FAN) and total ammonia nitrogen (TAN) were 84.0 ± 16.1 and 1163.0 ± 108.6 mg L −1 , respectively. Normalized capillary suction time (NCST) and solid content of thickened sludge obtained by centrifuging sludge increased with increasing TS. On day 49, NCST were 1.2 ± 0.2 (TS = 2%) and 13.2 ± 1.1 (TS = 10%) s g −1 -TS. Meanwhile, solid content of thickened sludge was 7.5 ± 0.5 (TS = 2%) and 15.4 ± 0.0% (TS = 10%). In summary, high VBPR and dewatering effects were obtained after TS content optimization. [ABSTRACT FROM AUTHOR]

The role of total solids content on sludge thermophilic anaerobic digestion was investigated in batch reactors. A range of total solids content from 2% to 10% was evaluated with two replicates. The lowest inhibitory concentration for free ammonia and total ammonia of sludge thermophilic anaerobic digestion was 110.9–171.4 mg/L and 1313.1–1806.7 mg/L, respectively. The volumetric biogas production rate increased with increasing of total solids content, but the corresponding biogas yield per gram volatile solid decreased. The result of normalized capillary suction time indicated that the dewaterability of digested sludge at high total solids content was poor, while solid content of sediment obtained by centrifuging sludge at 2000 g for 10 min increased with increasing of total solids content of sludge. The results suggest that thickened sludge mixed with dewatered sludge at an appropriate ratio could get high organic loading rate, high biogas yield and adequate dewatering effort. [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 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]

[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]