Reclamation of Real Urban Wastewater Using Solar Advanced Oxidation Processes: An Assessment of Microbial Pathogens and 74 Organic Microcontaminants Uptake in Lettuce and Radish

Abstract

In this study, disinfection of urban wastewater (UWW) with two solar processes (H2O2-20 mg/L, and photo-Fenton 10 mg/L-Fe 2+ /20 mg/L-H2O2 at natural water pH) at pilot scale using a 60L-Compound Parabolic Collector reactor for irrigation of raw-eaten vegetables (lettuce and radish) has been investigated. Several microbial targets (total coliforms, Escherichia coli, Salmonella spp, and Enterococcus spp) naturally occurring in UWW and 74 organic microcontaminants (OMCs) were monitored. Disinfection results showed no significant differences between both processes, showing the following inactivation resistance order: Salmonella spp. < E. coli < total coliforms < Enterococcus spp. Reductions of target microorganisms to concentrations below the limit of detection (LOD) was achieved in all cases with cumulative solar UV (QUV) ranged from 12 to 40 kJ/L (90 min to 5 hours). Solar photo-Fenton showed a reduction of 66% of OMCs and solar/H2O2 of 56% in 4 hours treatment. Irrigation of radish and lettuce with solar treated effluents, secondary effluents and mineral water was performed for 6 and 16 weeks, respectively. The presence of bacteria was monitored in surfaces and uptake of leaves, fruit and also in soil. The bacterial concentrations detected were below the LOD in the 81.2% (lettuce) and the 87.5% (radish) of the total number of samples evaluated. Moreover, uptake of OMCs was reduced above 70% in crops irrigated with solar treated effluents in comparison with secondary effluents of UWW.

Molecular biological methods in environmental engineering

“…In areas where water resources are scarce, urban wastewater will be reused to irrigate farmland (Aguas et al, 2019). However, high-quality treated wastewater will still affect the community composition of natural microorganisms and promote the transfer of antibiotic resistance genes (ARGs) among microorganisms (Amirsoleimani, Brion, Diene, François, & Richard, 2019;Subirats et al., 2019).…”

Worldwide Research Trends on Solar-Driven Water Disinfection

“…Even the mere sunlight-H 2 O 2 combination has recently been considered as a sustainable option, compared to other solar-powered AOPs in advanced municipal wastewater treatment plants (WWTPs), for reuse in crop irrigation [43]. Recent articles clearly show the current research trends in this area, including the investigation of microbial risks associated to the practice of WW reclaim in agriculture [44], the implementation of large-scale continuous solar treatments [29] and the control of emerging pathogens, such as antimicrobial resistance for irrigation and food production [45].…”

Bimolecular versus Trimolecular Reaction Pathways for H2O2 with Hypochlorous Species and Implications for Wastewater Reclamation

“…Hydroxyl radical (OH • )-based advanced oxidation technologies (AOTs) are able to remove organic pollutants and control pathogenic microorganisms, and they are considered an effective way to improve the quality of reclaimed water. , The benchmark AOT is the combination of ultraviolet (UV) light and hydrogen peroxide (H 2 O 2 ), an inexpensive and readily available chemical. , The photochemical formation of OH • from H 2 O 2 is triggered by UV irradiation . However, the UV molar extinction coefficient ( ε ) of H 2 O 2 is remarkably low (19.6 M –1 cm –1 at 254 nm), indicating that UV irradiation is inefficient in initiating the OH • formation reaction.…”