Solar processes and ozonation for fresh-cut wastewater reclamation and reuse: Assessment of chemical, microbiological and chlorosis risks of raw-eaten crops.

In this study, a full cycle of agricultural reuse of agro-food wastewater (synthetic fresh-cut wastewater, SFCWW) at pilot plant scale has been investigated. Treated SFCWW by ozonation and two solar processes (H2O2/solar, Fe3+-EDDHA/H2O2/solar) was used to irrigate two raw-eaten crops (lettuce and radish) grown in peat. Two foodborne pathogens (E. coli O157:H7 and Salmonella enteritidis) and five organic microcontaminants (OMCs: atrazine, azoxystrobin, buprofezin, procymidone and terbutryn) were monitored along the whole process. The three studied processes showed a high treatment capability (reaching microbial loads < 7 CFU/100 mL and 21-90 % of OMC reduction), robustness (based on 7 or 10 analysed batches for each treatment process) and high suitability for subsequent treated SFCWW safe reuse: non-phytotoxic towards Lactuca sativa and no bacterial regrowth during its storage for a week. The analysis of the harvested crop samples irrigated with treated SFCWW in all the studied processes showed an absence of microbial contamination (< limit of detection, LOD; i.e., < 1 CFU/99 g of lettuce and < 1 CFU/8 g of radish), a significant reduction of OMC uptake (in the range 40-60 % and > 90 % for solar treated and ozonated SFCWW, respectively) and bioaccumulation in both crops in comparison with the results obtained with untreated SFCWW. Moreover, the chlorophyll content in the harvested lettuces irrigated with SFCWW treated by Fe3+-EDDHA/H2O2/solar was twice than that irrigated with SFCWW treated by H2O2/solar and ozone, indicating the additional advantage of using Fe3+-EDDHA as an iron source to reduce the risk of iron chlorosis in crops. Finally, the chemical (dietary risk assessment for the combined exposure of the 5 OMCs) and quantitative microbiological risk assessment (QMRA) of the harvested crops showed the capability of the studied processes to reduce the risk associated with untreated SFCWW reuse by more than 50 % and more than 4 orders of magnitude, respectively.

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

In this study, disinfection of urban wastewater (UWW) with two solar processes (H2O2 -20 mg/L and photo-Fenton 10 mg/L-Fe2+/20 mg/L-H2O2 at natural water pH) at pilot scale using a 60 L compound parabolic collector reactor for irrigation of two 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 energy per volume (QUV) ranged from 12 to 40 kJ/L (90 min to 5 h). Solar photo-Fenton showed a reduction of 66% of OMCs and solar/H2O2 of 56% in 5 h 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.

Determination of pesticide levels in wastewater from an agro-food industry: Target, suspect and transformation product analysis.

Agriculture is considered as the main source of water contamination by pesticides. However, food packaging or processing industries are also recognised as relevant point sources of contamination by these compounds, not yet investigated in depth. The objective of this work has been to improve current knowledge about the presence and concentration of pesticides in the effluent of a food processing industry, as well as to investigate their main transformation products (TPs). An analytical strategy combining target and suspect analysis has been applied to provide an evaluation of the effluents. The methodology involves solid-phase extraction (SPE) of wastewater samples followed by (i) liquid chromatography quadrupole-linear ion trap tandem mass spectrometry (LC-QqLIT-MS/MS) for quantitative target analysis and (ii) liquid chromatography coupled to quadrupole-time-of-flight high resolution mass spectrometry (LC-QTOF-HRMS) to identify non-target pesticides and possible TPs. The results revealed the presence of 17 of the target pesticides analysed and 3 additional ones as a result of the suspect screening performed by HRMS. The TPs were investigated for the pesticides found at the highest concentrations: imazalil (7038-19802 ng/L), pyrimethanil (744-9591 ng/L) and thiabendazole (341-926 ng/L). Up to 14 TPs could be tentatively identified, demonstrating the relevance of this type of studies. These data provide a better understanding of the occurrence of pesticides and their TPs in agro-food industrial effluents.