Table 2. Performance of the mesophilic and thermophilic reactors at different OLRs under steady state conditions.

Parameters

Mesophilic reactor (37ºC)

Thermophilic reactor (55ºC)

HRT 7 days
OLRs (g[COD]/L/day)

HRT 7 days
OLRs (g[COD]/L/day)

HRT 5 days
OLRs (g[COD]/L/day)

9.72

10.74

12.25

9.62

10.82

12.15

15.15

17.01

pH

7.54 ± 0.04^b

7.44 ± 0.03^a

7.42 ± 0.03^a

7.80 ± 0.03^d

7.72 ± 0.04^c

7.72 ± 0.04^c

7.72 ± 0.03^c

7.71 ± 0.03^c

TVFA
(mg as acetic acid/L)

172.29 ± 8.94^a

631.86 ± 10.15^e

815.43 ± 12.82^g

270.14 ± 21.93^b

493.29 ± 11.39^c

537.14 ± 11.00^d

734.29 ± 19.25^f

980.00 ± 15.43^h

Alkalinity (mg/L)

3,000.00 ± 16.98^a

3,156.57 ± 10.71^c

3,157.14 ± 20.04^c

3,126.79 ± 22.92 ^b

3,144.64 ± 34.92 ^bc

3,150.21 ± 32.27^c

3,451.79 ± 21.29^e

3,227.68 ± 26.93^d

TVFA/alkalinity

0.06 ± 0.00^a

0.20 ± 0.00^e

0.26 ± 0.00^g

0.09 ± 0.01^b

0.16 ± 0.01^c

0.17 ± 0.00^d

0.21 ± 0.01^f

0.30 ± 0.01^h

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

2.81 ± 0.04^b

3.36 ± 0.03^d

3.73 ± 0.05^e

2.70 ± 0.05^a

3.30 ± 0.02^c

3.81 ± 0.04^f

4.06 ± 0.05^g

4.66 ± 0.03^h

Gas yield (L/g[COD])

0.66 ± 0.01^b

0.71 ± 0.01^e

0.69 ± 0.01^c

0.66 ± 0.01^b

0.70 ± 0.01^d

0.70 ± 0.01^d

0.63 ± 0.0^a

0.62 ± 0.01^a

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

1.96 ± 0.03^b

2.39 ± 0.05^d

2.65 ± 0.04^e

1.91 ± 0.04^a

2.31 ± 0.03^c

2.68 ± 0.03 ^f

2.82 ± 0.06^g

3.24 ± 0.04^h

Methane yield (L/g[COD])

0.46 ± 0.01^b

0.51 ± 0.01^e

0.49 ± 0.01^d

0.47 ± 0.01^c

0.49 ± 0.01^d

0.49 ± 0.01^d

0.44 ± 0.01^a

0.44 ± 0.05^a

COD reduction (%)

69.89 ± 0.65^c

70.44 ± 0.33^d

71.10 ± 0.31^e

67.73 ± 0.63^a

69.88 ± 0.15^c

72.16 ± 0.33 ^f

68.20 ± 0.24^b

70.32 ± 0.30^d