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The sunlight/H2O2 process has recently been considered as a sustainable alternative option compared to other solar driven advanced oxidation processes (AOPs) in advanced treatment of municipal wastewater (WW) to be reused for crop irrigation. Accordingly, in this study sunlight/H2O2 was used as disinfection/oxidation treatment for urban WW treatment plant effluent in a compound parabolic collector photoreactor to assess subsequent cross-contamination of lettuce and soil by contaminants of emerging concern (CECs) (determined by QuEChERS extraction and LC-QqLIT-MS/MS analysis) and antibiotic resistant (AR) bacteria after irrigation with treated WW. Three CECs (carbamazepine (CBZ), flumequine (FLU), and thiabendazole (TBZ) at 100 μg L(-1)) and two AR bacterial strains (E. coli and E. faecalis, at 10(5) CFU mL(-1)) were spiked in real WW. A detection limit (DL) of 2 CFU mL(-1) was reached after 120 min of solar exposure for AR E. coli, while AR E. faecalis was more resistant to the disinfection process (240 min to reach DL). CBZ and TBZ were poorly removed after 90 min (12% and 50%, respectively) compared to FLU (94%). Lettuce was irrigated with treated WW for 5 weeks. CBZ and TBZ were accumulated in soil up to 472 ng g(-1) and 256 ng g(-1) and up-taken by lettuce up to 109 and 18 ng g(-1), respectively, when 90 min treated WW was used for irrigation; whereas no bacteria contamination was observed when the bacterial density in treated WW was below the DL. A proper treatment time (>90 min) should be guaranteed in order to avoid the transfer of pathogens from disinfected WW to irrigated crops and soil.

The continuous release of chemical and microbiological pollutants into the environment and the increasing demand for safe water call for effective water and wastewater treatment processes. In particular, the detection of resistant microorganisms (e.g. antibiotic-resistant bacteria) in the effluents of urban wastewater treatment plants disposed into surface water or reused (e.g. in crop irrigation) shows that conventional treatments and disinfection processes do not effectively control the spread of pathogens into the environment. There is a need for new and more effective disinfection processes and technologies. The aim of this chapter is to briefly describe some of the emerging and antimicrobial-resistant microorganisms detected in wastewater, as well as the conventional and new advanced available technologies for wastewater disinfection, and to evaluate and discuss their effect on these microorganisms. Moreover, regulations and policies on wastewater reuse are also critically discussed and compared.

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