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Table 3 The early warning indicators of R2

From: Early warning indicators for mesophilic anaerobic digestion of corn stalk: a combined experimental and simulation approach

Reactor Parameters Units Date of abrupt change (day) Date of process failure (day) Warning time (day) Experimental results Simulated results
Abrupt changea Abrupt vs. steady-state value Abrupt change Abrupt vs. steady-state value
R2 CH4/CO2 161 160 0 1.00 − 36.31 to − 25.48% 0.86 − 18.01 to − 21.33%
Acetate g/L 153 160 7 0.52 + 57.58 to 73.33% 0.43 + 36.43 to 303.98%
Propionate g/L 155 160 5 0.98 + 390.00 to 444.44% 0.12 + 27.64 to 206.45%
VFA g/L 155 160 5 2.15 + 225.76 to 305.66% 0.80 + 76.84 to 193.84%
IA g CaCO3/L 153 160 7 0.87 + 37.09 to 62.18% 0.32 + 36.66 to 138.60%
BA** g CaCO3/L 154 160 6 1.04 − 34.29 to − 22.27% 0.89 − 60.09 to − 11.46%
VFA/BA 155 160 5 0.64 + 36.17 to 88.24% 0.94 + 106.41 to 338.75
BA/TA 154 160 6 0.52 − 36.59 to − 28.77% 0.71 − 25.57 to − 13.03%
IA/BA 153 160 7 0.68 + 47.83 to 65.95% 0.34 + 24.32 to 99.59%
pH 160 6.33 <6.4
CH4 yield*** L CH4/g VS 163 0.09 0.07 − 69.97 to 52.38%
  1. aValues in the units indicated in the “Parameters” column
  2. bBA in simulated results expressed as the absolute change in the sum of dissolved HCO3 and CO32− over half a day, in %
  3. cThe values in brackets refer to the corresponding values of sudden overload. − means decrease, and + means increase