The activity test was conducted at 35 ± 1 C in a shaking water bath (Yamato BT200). Every 2 h gas production,
composition and sulfate concentration was measured to determine the extent of methane production and sulfate reduction. Furthermore,methane production and sulfate reduction at different intervals were converted into COD removal according to stoichiometry (1 L CH4 2.857 g COD; 1 g SO42 0.6667 g COD). In this way the SMA and SSA using different substrates were obtained by the curve slope of the methane production rate and sulfate reduction rate according to the equations: