Skip to main content

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