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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]

In anaerobic digestion (AD) of sludge, AD efficiency and digested sludge (DS) dewaterability are critical factors. In this study, polyester non-woven fabric fillers were integrated into a sludge digester. The effect of such fillers on digestion was investigated in thermophilic temperature range in semi-continuous mode. Methane production of filler system and control reactor were significantly different ( P < 0.05, paired t -test). At hydraulic retention times of 18 days and 12 days, the corresponding methane yields from filler system were 140% and 161%, respectively, of the yields from control digester without filler. Improvement of DS dewaterability was uncertain during 110 days of operation. While after a longer period of digestion, filler system resulted in a lower normalized capillary suction time of DS (76.5 ± 21.6 s L/g total suspended solids) than control reactor (118.7 ± 32.9 s L/g total suspended solids). The results showed that the filler could improve thermophilic AD performance, except at too short hydraulic retention times. [ABSTRACT FROM AUTHOR]