Kinetics of para-nitrophenol and chemical oxygen demand removal from synthetic wastewater in an anaerobic migrating blanket reactor

A laboratory scale anaerobic migrating blanket reactor (AMBR) was operated at different HRTs (1-10.38 days) in order to determine the para-nitrophenol (p-NP) and COD removal kinetic constants. The reactor was fed with 40 mg L-1 p-NP and 3000 mg L-1 glucose-COD. Modified Stover-Kincannon and Grau second-order kinetic models were applied to the experimental data. The predicted p-NP and COD concentrations were calculated using the kinetic constants. It was found that these data were in better agreement with the observed ones in the modified Stover-Kincannon compared to Grau second-order model. The kinetic constants calculated according to Stover-Kincannon model are as follows: the saturation value constant (KB) and maximum utilization rate constants (R-max) were found as 31.55 g COD L-1 day(-1), 29.49 g CODL-1 day(-1) for COD removal and 0.428 g p-NP L-1 day(-1), 0.407 g p-NPL-1 day(-1) for p-NP removal, respectively (R-2 = 1). The values of(a) and (b) were found to be 0.096 day and 1.071 (dimensionless) with high correlation coefficients of R-2 = 0.85 for COD removal. Kinetic constants for specific gas production rate were evaluated using modified Stover-Kincannon, Van der Meer and Heerrtjes and Chen and Hasminoto models. it was shown that Stover-Kincannon model is more appropriate for calculating the effluent COD, p-NP concentrations in AMBR compared to the other models. The maximum specific biogas production rate, G(max), and proportionality constant. GB, were found to be 1666.7 mL L-1 day(-1) and 2.83 (dimensionless), respectively in modified Stover-Kincannon gas model. The bacteria had low Haldane inhibition constants (K-ID = 14 and 23 mg L-1) for p-NP concentrations higher than 40 mg L-1 while the half velocity constant (K,) increased from 10 to 60 and 118 mg L-1 with increasing p-NP concentrations from 40 to 85 and 125 mg L-1. (C) 2008 Elsevier B.V. All rights reserved