Removal of pharmaceuticals in hospital wastewater by solar photo-Fenton with Fe3+-EDDS using a pilot raceway pond reactor: Transformation products and in silico toxicity assessment

Abstract

This study investigated the removal of six representative pharmaceuticals (PHCs), including dipyrone (DIP), diazepam (DZP), fluoxetine (FXT), paracetamol (PCT), propranolol (PPN), and progesterone (PRG) at 500 µg L−1 in raw hospital wastewater (RHWW) treated by solar photo-Fenton with Fe3+-EDDS in a pilot raceway pond reactor (RPR). The effect of the molar ratio (1:1 and 1:2) on the degradation of PHCs and formation of their transformation products (TPs) during the treatments were studied. Additionally, Quantitative Structure-Activity Relationships (Q)SAR in silico toxicity predictions for all TPs identified were evaluated. Experiments were carried out under natural sunlight with a total volume of 10 L of RHWW. The reactant concentrations were PHCs(mix) (500 µg L−1), Fe3+-EDDS (1:2 and 1:1; 15.35 mg L−1 of iron) and H2O2 (230 mg L−1), with all experiments at circumneutral pH. The H2O2 was carefully dosed during the first 30 min of solar photo-Fenton treatment to avoid its continued excess and inefficient use. The main results obtained indicate the degradation of PHCs is highly favored in Fe3+:EDDS (1:2) providing total consumption of H2O2, increased iron stability, degradation percentages above 77% in most PHCs and total degradation of some TPs formed throughout the process at t30W = 57 min. Twenty-one TPs were identified using LC-QTOF MS associated with a purpose-built database for both molar ratio (1:1 and 1:2) of Fe3+-EDDS. To perform the (Q)SAR predictions of the PHCs and TPs identified, the toxicity, biodegradability, mutagenicity, and bioaccumulation were calculated on the basis of in silico tools. Principal component analysis (PCA) was also performed to compare the toxicity of the TPs, allowing the consideration of two principal components which characterized 88% of the predicted results. Most of the TPs did not show toxicity, mutagenicity or bioaccumulation characteristics.