Microcontaminant removal in secondary effluents by solar photo-Fenton at circumneutral pH in raceway pond reactors

This paper deals with raceway pond reactors (RPRs) as an alternative photoreactor for solar photo-Fenton applications. Raceway pond reactors are common low-cost reactors which can treat large volumes of water. The experiments were carried out with Fe3+:EDDS complex in the secondary effluent of a municipal wastewater treatment plant spiked with a mixture of 100 mu g/L each of five pharmaceuticals (carbamazepine, flumequine, ibuprofen, ofloxacin and sulfamethoxazole) at circumneutral pH. In a preliminary stage, two operating strategies, sequential addition of iron sulfate and Fe3+:EDDS complex at a 1:2 molar ratio were compared, and Fe3+:EDDS complex was found to be the best option. The effect of liquid depth (10, 15 and 20 cm) was also explored. 90% pharmaceutical removal was achieved with accumulated solar UV energy of around 1 kJ/L. Finally, RPRs and tubular photoreactors with compound parabolic collectors (CPC) were compared under realistic conditions. Pharmaceutical removal efficiency was four times higher, increasing from 0.26 mg/kJ with CPC reactors to 1.07 mg/kJ in the 15-cm-deep RPR. As far as the authors know, this is the first detailed study on the effect of liquid depth in RPRs at circumneutral pH. (C) 2016 Elsevier B.V. All rights reserved.