Neutral or acidic pH for the removal of contaminants of emerging concern in wastewater by solar photo-Fenton? A techno-economic assessment of continuous raceway pond reactors

Abstract

As far as the authors know, no in-depth comparison has been made between the different performances of the solar photo-Fenton process for the removal of contaminants of emerging concern (CECs) as a function of pH. To this end, real WWTP secondary effluents were treated in continuous flow mode at pilot plant scale. The effect of hydraulic residence time (HRT), liquid depth and percentage of CEC removal on treatment capacity was studied. At acidic pH (2.8), the iron source was FeSO4 and at neutral pH (7.0), it was Fe(III)-EDDS. At both pH values, 2250 L m−2 d−1 can be treated in 15-cm deep raceway pond reactors at 30 min HRT with 0.1 mM iron and 0.88 mM H2O2 in order to achieve 80% CEC removal. Treatment costs were 0.25 € m−3 and 0.56 € m−3 at acidic and neutral pH, respectively. This study paves the way for the solar photo-Fenton process to be employed on a commercial scale.