Table 5. Performance of the thermophilic reactor at different operating temperatures under steady-state conditions.

Parameters

Temperature (ºC)

Phase I

Phase III

55

52

49

46

43

37

 pH

7.78 ± 0.04^c

7.78 ± 0.04^c

7.76 ± 0.04^c

7.60 ± 0.13^a

7.69 ± 0.13^b

7.57 ± 0.04^a

 TVFA (mg as acetic acid/L)

274.86 ± 8.99^c

256.43 ± 14.64^b

239.71 ± 12.44^a

284.29 ± 6.30^d

746.14 ± 6.05^e

851.29 ± 7.96^f

 Alkalinity (mg/L)

3,122.32 ± 23.6^bc

3,114.29 ± 16.16^bc

3,117.86 ± 34.22^bc

3,134.82 ± 25.09^c

3,058.93 ± 27.49^a

3,106.79 ± 21.15^b

 TVFA/Alkalinity

0.09 ± 0.00^c

0.08 ± 0.00^b

0.07 ± 0.00^a

0.09 ± 0.00^c

0.24 ± 0.00^d

0.27 ± 0.00^e

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

2.71 ± 0.02^de

2.72 ± 0.02^e

2.69 ± 0.03^cd

2.67 ± 0.06^c

2.53 ± 0.03^b

2.24 ± 0.02^a

 Gas yield (L/g[COD])

0.65 ± 0.01^c

0.66 ± 0.01^d

0.65 ± 0.01^c

0.65 ± 0.01^c

0.62 ± 0.01^b

0.56 ± 0.01^a

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

1.86 ± 0.02^c

1.89 ± 0.02^d

1.89 ± 0.02^d

1.89 ± 0.04^d

1.77 ± 0.02^b

1.55 ± 0.02^a

 Methane yield (L/g[COD])

0.44 ± 0.01^c

0.46 ± 0.01^d

0.46 ± 0.01^d

0.46 ± 0.01^d

0.43 ± 0.01^b

0.39 ± 0.00^a

 COD reduction (%)

69.27 ± 0.06^d

68.26 ± 0.48^c

68.54 ± 0.45^c

67.80 ± 0.43^b

67.65 ± 0.69^b

65.71 ± 0.32^a