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Table 4 Comparison of data from the foaming digesters D1 and D2 (biogas plant BP A)

From: Foam formation in full-scale biogas plants processing biogenic waste

Time of sampling   Two weeks before foaming Day 1 of foaming One week after foaming
Digester Index D1 D2 D1 D2 D1 D2
TS [%] O 3.53 1.77 4.17 3.45 3.25 2.85
VS [% TS] O 56.5 33.5 66.0 64.4 52.1 45.6
pH [−] CE 8.08 8.06 8.12 8.03 7.87 8.12
VFA/TIC [−] CE/CA 0.16 0.13 0.11 0.12 0.09 0.11
NH4-N [g/L] F 2.81 3.09 2.50 2.06 2.04 2.31
Total organic carbon [g/L] B 6.52 5.44 11.1 8.68 9.10 11.26
Total nitrogen [g/L] B 4.31 4.32 4.62 4.29 4.23 4.31
Crude protein [g/L] CA 9.34 7.62 13.2 13.9 13.6 12.5
Acetic acid [mg/L] F 159 182 31.4 26.5 29.5 76.7
Propionic acid [mg/L] F <1 <1 <1 <1 <1 <1
Butyric acid [mg/L] F <1 <1 <1 <1 <1 <1
Calcium [mg/L] F 12.0 48.0 41.0 58.6 43.5 21.0
Magnesium [mg/L] F 1.41 7.23 5.05 6.06 5.91 2.31
Phosphorus [mg/L] F 300 284 316 305 248 190
Potassium [mg/L] F 1,148 1,188 1,130 1,159 1,096 1,190
Sulfur [mg/L] F 301 297 379 332 345 324
Surface tension [mN/m] CE 57.7 57.0 60.7 60.2 58.0 57.0