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Table 2 Chemical characterization of the digestate of the methanogenic reactors R1 and R2 during foaming

From: Floating layer formation, foaming, and microbial community structure change in full-scale biogas plant due to disruption of mixing and substrate overloading

  Two days before foaming One day after foaming Five days after foaming
R1 R2 R1 R2 R1 R2
VOA/TIC (-) 0.093 ± 0.006 0.098 ± 0.008 0.170 ± 0.023 0.155 ± 0.002 0.134 ± 0.036 0.0173 ±0.038
Total carbon (g L-1) 16.42 ± 0.86 15.55 ± 0.69 18.63 ± 1.23 13.67 ± 0.30 15.87 ± 0.58 15.80 ± 0.66
Total organic carbon (g L-1) 12.23 ± 0.76 11.44 ± 0.64 14.04 ± 0.52 9.793 ± 250 11.87 ± 0.51 11.75 ± 0.66
Total nitrogen (g L-1) 4.63 ± 0.24 4.57 ± 0.19 5.14 ± 0.14 4.60 ± 0.15 4.21 ± 0.05 4.28 ± 0.05
Ammonia nitrogen (g L-1) 2.61 ± 0.03 2.69 ± 0.02 2.83 ± 0.01 2.85 ± 0.01 2.94 2.98
Crude protein (g L-1) 12.67 11.73 14.42 10.97 7.95 8.16
Volatile organic acids:       
Acetic acid (mg L-1) <1 126 407 207 215 551
Propionic acid (mg L-1) <1 <1 <1 66 <1 <1
Butyric acid (mg L-1) <1 <1 <1 <1 <1 <1
Water-eluable elements       
Calcium (mg L-1) 43.4 56.5 54.3 86.0 36.3 61.8
Iron (mg L-1) 5.33 5.56 5.20 4.88 4.26 6.91
Magnesium (mg L-1) 4.57 5.81 6.30 12.5 11.4 9.63
Nickel (mg L-1) <4 <4 21.4 20.8 <4 <4
Phosphorus(mg L-1) 132 145 161 139 151 151
Potassium (mg L-1) 1,703 1,687 1,682 1,659 1,755 1,690
Sulfur (mg L-1) 46.6 43.2 56.9 43.1 47.3 49.6
  1. In case of multiple determinations, standard deviations are presented.