Subsequently, the reactor performance decreased substantially after the addition of 45 mg/L of SMX. The average effluent soluble COD concentration of the reactor was 815.5 ± 591.6 mg/L. The authors mentioned in their previous study that the significant shortterm
effect of SMX started between 100–250 mg/L. The complete inhibition effect on both biogas production and COD removal was observed approximately 500 mg/L and higher concentrations of SMX