Sorption and inhibitory effect of octylphenol ethoxylate Triton X-100 on methanogenic and denitrifying granular sludges

The aims of this work were to characterize the sorption and evaluate the inhibitory effect of octylphenol ethoxylate Triton X-100 (OPEOTx) on methanogenic and denitrifying sludges. According to Langmuir isotherm, maximums OPEOTx sorption values on methanogenic and denitrifying sludges were 60.70 mg (gVSS)^-1 and 87.47 mg (gVSS)^-1 respectively. The specific removal rate of chemical oxygen demand (r_COD) and the accumulated volume biogas (V_BG) were used to evaluate the OPEOTx inhibitory effect on sludges. Experimental inhibition data were fitted to the models of non-competitive inhibition and modified Gompertz. Methanogenic sludges reached higher levels inhibition in the r_COD and biogas production potential P_max (84.0 and 88.5%) comparing with denitrifying sludges (24.3 and 21.9%). Furthermore, in all OPEOTx concentrations, carbohydrates-proteins quotient value of the extracellular polymeric substances for the denitrifying sludges remained below respect to the same quotient in methanogenic sludges. The above contributes in part to explain the greater sorption capacity of the denitrifying sludges by OPEOTx and their granules resistance to be damaged by OPEOTx amphiphilic nature. The study gives insights to understand OPEOs interactions and their effects on methanogenic and denitrifying granular sludges.