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

Abstract

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 ( K B) and maximum utilization rate constants ( R max) were found as 31.55 g COD L −1 day −1, 29.49 g COD L −1 day −1 for COD removal and 0.428 g p-NP L −1 day −1, 0.407 g p-NP L −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, G B, 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 s) increased from 10 to 60 and 118 mg L −1 with increasing p-NP concentrations from 40 to 85 and 125 mg L −1.