Peroxymonosulfate/Solar process for urban wastewater purification at a pilot plant scale: A techno-economic assessment.

The safe reuse of reclaimed water for agricultural irrigation has been considered as an alternative, feasible and sustainable option to address water scarcity. This work aims to validate the capability of the solar water photochemical process based on the synergistic effect between peroxymonosulfate (PMS) and natural solar radiation for actual urban wastewater (UWW) purification at a pilot plant scale using a solar Compound Parabolic Collector photo-reactor. The PMS/Solar process performance was assessed by monitoring simultaneously the inactivation of naturally occurring bacteria (Escherichia coli, Total coliforms, Enterococcus spp. and Pseudomonas spp.) as a potential tertiary treatment to fit the minimum bacterial requirements for UWW purification but also additional challenges have been in deep analysed simultaneously. In this regard, a global analysis including the degradation of three Contaminants of Emerging Concern (CECs) (Diclofenac-DCF, Sulfamethoxazole-SMX and Trimethoprim-TMP), the removal of antibiotic resistant elements, the residual toxicity and the treatment cost has been analysed. Different PMS concentrations (0-1 mM) were tested and an enhancement in the process performance was obtained with increasing oxidant load, obtaining the best results with 1 mM of PMS, at which detection limit (DL) of 2 CFU/mL was reached for all microbial targets after 15 min (1.1 kJ/L of accumulated solar UV-A radiation (Q)) and 80 % of CECs removal was reached after 27 min (2.0 kJ/L of Q) of solar treatment time. Inactivation of naturally occurring antibiotic resistant bacteria (ARB) and removal of 16S rRNA and selected antibiotic resistance genes (ARGs) (i.e., intI1, sul1, qnrS, bla, bla, tetM) were also investigated. ARB was successfully inactivated to values below the DL, but the process was not able to completely remove ARGs. A total reduction of intI1 (30 %), 16S rRNA (19 %), sul1 (14 %), bla (12 %), qnrS (10 %), bla (8 %), and tetM (7 %), was obtained after 120 min (11.5 kJ/L of Q). An absence of an eco and phytotoxic effect of treated samples was observed towards Aliivibrio fischeri and three seeds, respectively. Finally, an estimated treatment cost of 0.96 €/m for the simultaneous UWW disinfection and decontamination demonstrates the promising capability of this solar treatment for UWW reclamation and reuse in agriculture, especially in areas with a high solar radiation incidence.