Skip to main content

Table 1 Physical and coded values of the variables used in the central composite design

From: Revealing the factors influencing a fermentative biohydrogen production process using industrial wastewater as fermentation substrate

Coded symbol Variables Values of coded levels
(-1.28) (-1) (0) (+1) (+1.28)
X1 Operating temperature (°C) 23.28 25 31 37 38.72
X 2 Initial value of fermentation pH 4.56 4.8 5.65 6.5 6.74
X3 Glucose addition (g/L) 3.56 5 10 15 16.44