Endocrine disrupter compounds removal in wastewater using microalgae: Degradation kinetics assessment

This paper describes a study carried out to determine the removal kinetics of four micropollutants (4-tert-octylphenol (OP), technical-nonylphenol (t-NP), 4-nonylphenol (4-NP) and bisphenol-A (BPA)) usually found in wastewater streams. The kinetic experiments were carried out in batch reactors containing the effluent of an Anaerobic Membrane BioReactor (AnMBR) in the presence of light, oxygen and microalgae. As the degradation process of the studied micropollutants obeyed a pseudo-first-order kinetics, the second-order kinetics for each micropollutant was then calculated. The second order rate constants for the hydroxyl radical (k.(OH)) ranged from 7.0.10(+10) to 6.6.10(+12) L.mol(-1).min(-1) and for the oxygen (k(O2)) from 77 to 125 L.mol(-1).min(-1). The k(O2) values were significantly lower than the k% OH values, indicating that the hydroxyl radical is a better oxidising agent than oxygen. However, as the concentration of dissolved oxygen was higher than that of the hydroxyl radical, higher oxygen pseudo-first order rate constants were produced (k(O2), ranging from 0.016 to 0.026 min(-1)) than hydroxyl radical pseudo-first order rate constants (k.(OH), ranging from 7.0.10-05 to 6.6.10-03 min(-1)), bringing the degradation process under the control of the oxygen mechanism. The proposed kinetic model was validated by fitting experimental data from a study of supersaturated oxygen concentration and showed good correlation for all the studied micropollutants.