Tertiary treatment of urban wastewater by solar and UV-C driven advanced oxidation with peracetic acid: effect on contaminants of emerging concern and antibiotic resistance

Photo driven advanced oxidation process (AOP) with peracetic
acid (PAA) has been poorly investigated in water and wastewater treatment
so far. In the present work its possible use as tertiary treatment of
urban wastewater to effectively minimize the release into the environment
of contaminants of emerging concern (CECs) and antibiotic resistant
bacteria was investigated. Different initial PAA concentrations, two
light sources (sunlight and UV-C) and two different water matrices
(groundwater (GW) and wastewater (WW)) were studied. Low PAA doses were
found to be effective in the inactivation of antibiotic resistant
Escherichia coli (AR E. coli) in GW, being UV-C driven process faster
(detection limit (DL) achieved for a cumulative energy (QUV) of 0.3 kJL-1
with 0.2 mg PAA L-1) than solar driven one (DL achieved at QUV=4.4 kJL-1
with 0.2 mg PAA L-1). Really fast inactivation rates of indigenous AR E.
coli were observed in WW. Higher QUV and PAA initial doses were necessary
to effectively remove the three target CECs (carbamazepine (CBZ),
diclofenac and sulfamethoxazole), being CBZ the more refractory one. In
conclusion, photo driven AOP with PAA can be effectively used as tertiary
treatment of urban wastewater but initial PAA dose should be optimized to
find the best compromise between target bacteria inactivation and CECs
removal as well as to prevent scavenging effect of PAA on hydroxyl
radicals because of high PAA concentration.