Table 4. Performance of the mesophilic reactor at different operating temperatures under steady-state conditions.

Parameters

Temperature (ºC)

Phase I

Phase III

37

40

43

49

52

55

 pH

7.55 ± 0.05^a

7.57 ± 0.03^a

7.61 ± 0.02^b

7.68 ± 0.07^c

7.73 ± 0.04^d

7.80 ± 0.03^e

 TVFA (mg as acetic acid/L)

166.64 ± 7.44^a

162.43 ± 8.31^a

160.71 ± 6.73^a

338.71 ± 14.87^c

253.07 ± 7.32 ^b

245.07 ± 15.32^b

 Alkalinity (mg/L)

3,051.00 ± 33.70^b

3,053.79 ± 32.74^b

3,061.71 ± 31.58 ^b

2,981.43 ± 31.31^a

2,974.36 ± 23.82^a

2,984.14 ± 28.34^a

 TVFA/Alkalinity

0.06 ± 0.00^b

0.05 ± 0.00^a

0.05 ± 0.00^a

0.11 ± 0.01^d

0.08 ± 0.00^c

0.08 ± 0.00^c

 Biogas production
 (L of gas/L[reactor]/day)

2.81 ± 0.03^d

2.79 ± 0.02^d

2.80 ± 0.03^d

2.54 ± 0.02^a

2.65 ± 0.03^b

2.70 ± 0.02^c

 Gas yield (L/g[COD])

0.66 ± 0.01^d

0.65 ± 0.01^c

0.66 ± 0.01^d

0.61 ± 0.01^a

0.64 ± 0.01^b

0.66 ± 0.01^d

 Methane production
 (L/L[reactor]/day)

1.97 ± 0.02^c

1.97 ± 0.02^c

1.98 ± 0.02^c

1.72 ± 0.16^a

1.86 ± 0.02^b

1.91 ± 0.03^b

 Methane yield (L/g[COD])

0.46 ± 0.01^c

0.46 ± 0.01^c

0.46 ± 0.1^c

0.42 ± 0.01^a

0.45 ± 0.00^b

0.47 ± 0.01^d

 COD reduction (%)

70.34 ± 0.39^d

70.76 ± 0.02^e

70.85 ± 0.45^e

69.08 ± 0.92^c

68.31 ± 0.36^b

67.62 ± 0.40^a