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Table 3 Methane production and chemical characterization of effluent after AD

From: Enhanced methane production of vinegar residue by response surface methodology (RSM)

F/I ratio (X1) Organic loading (X2) (gVS L−1) Initial pH (X3) Methane production Final pH TAN (mg L−1) TA (mg CaCO3 L−1) VFA (mg L−1) VFA/TA
Experimental value (mL gVS−1) Predicted value (mL gVS−1)
0.7 20 6 145.27 136.50 6.78 ± 0.08 778.0 ± 38.1 3025.0 ± 35.4 33.99 ± 7.72 0.011
0.7 20 8 155.78 157.47 7.50 ± 0.01 809.0 ± 12.7 7050.0 ± 106.1 31.33 ± 4.38 0.004
0.7 40 6 159.27 152.57 7.24 ± 0.04 904.5 ± 23.3 4962.5 ± 53.0 30.38 ± 0.41 0.013
0.7 40 8 174.79 178.10 7.87 ± 0.01 978.5 ± 14.9 9437.5 ± 88.4 64.86 ± 1.59 0.003
1.3 20 6 92.89 87.04 6.93 ± 0.02 491.0 ± 4.2 3287.5 ± 17.7 70.40 ± 0.13 0.021
1.3 20 8 103.32 107.47 7.39 ± 0.03 562.0 ± 26.9 5087.5 ± 159.1 30.20 ± 3.78 0.006
1.3 40 6 145.35 141.11 6.89 ± 0.08 978.0 ± 18.4 3700.0 ± 106.1 67.86 ± 1.05 0.018
1.3 40 8 159.87 166.10 7.37 ± 0.02 820.5 ± 10.6 5875.0 ± 141.4 52.97 ± 3.24 0.009
0.5 30 7 198.90 203.90 7.69 ± 0.06 910.0 ± 18.4 9337.5 ± 159.1 22.27 ± 1.69 0.002
1.5 30 7 153.62 152.22 7.28 ± 0.03 610.0 ± 35.4 4762.5 ± 53.0 49.32 ± 0.39 0.010
1 13.18 7 102.80 106.79 7.29 ± 0.08 455.0 ± 17.0 3262.5 ± 159.1 16.33 ± 2.10 0.005
1 46.82 7 170.00 169.61 7.50 ± 0.05 901.5 ± 24.8 8562.5 ± 123.7 58.18 ± 5.15 0.007
1 30 5.32 77.59 91.56 6.66 ± 0.05 973.5 ± 7.8 3175.0 ± 70.7 118.24 ± 4.29 0.037
1 30 8.68 140.59 130.22 7.60 ± 0.01 820.0 ± 14.1 8112.5 ± 123.7 24.88 ± 1.77 0.003
1 30 7 168.33 168.60 7.40 ± 0.01 781.5 ± 27.6 5912.5 ± 53.0 28.46 ± 2.31 0.005
1 30 7 160.02 168.60 7.42 ± 0.01 807.5 ± 31.8 5725.0 ± 106.1 30.67 ± 1.68 0.005
1 30 7 175.53 168.60 7.38 ± 0.06 824.0 ± 29.7 5900.0 ± 106.1 27.88 ± 1.92 0.005
1 30 7 178.15 168.60 7.33 ± 0.07 789.0 ± 34.0 5862.5 ± 123.7 25.64 ± 0.69 0.004
1 30 7 162.53 168.60 7.43 ± 0.04 780.0 ± 22.6 6425.0 ± 141.4 30.17 ± 1.90 0.005
1 30 7 167.65 168.60 7.41 ± 0.06 824.0 ± 11.3 5862.5 ± 88.4 31.20 ± 0.53 0.005
  1. TAN total ammonia–nitrogen; TA total alkalinity; VFA volatile fatty acids