Effects of Mixing Ratio on Dewaterability of Digestate of Mesophilic Anaerobic Co-Digestion of Food Waste and Sludge

Dewaterability of anaerobic digestate influences the further disposal ways. The role of mixing ratio on anaerobic co-digestion of food waste (F) and sludge (S) was investigated under mesophilic condition. Five different mixing ratios (F; F/S = 3:1; F/S = 1:1; F/S = 1:3; S) were evaluated with two replicates. The specific biogas production (SBP) of five mixing ratios were 95.5, 105.6, 95.6, 435.5 and 344.0 mL g−1-VSadded respectively. Under S condition, normalized capillary suction time (NCST) was significant correlation with protein and polysaccharide of Slime. Under F condition, NCST was significant correlated with polysaccharide of Slime. Under other conditions, the NCST was no significant correlation with protein and polysaccharide of any layers of extracellular polymeric substances (EPS). NCST increased with the increasing of sludge ratio. On day 37, NCST were 3.4 ± 0.9, 72.1 ± 15.6, 164.2 ± 37.6, 179.2 ± 30.6 and 278.1 ± 56.1 s g−1-TS respectively. Adequate mixing ratio (around F/S = 1:3) of food waste and sludge under mesophilic anaerobic condition could result in high SBP. The dewaterability of anaerobic digestate deteriorated with the increasing of sludge ratio in mixture of sludge and food waste.