Effective management of water resources is crucial for global food security and sustainable development. In this Review, we explore the potential benefits and challenges associated with treated wastewater (TW) reuse for irrigation. Currently, 400 km³ yr⁻¹ of wastewater is generated globally, but <20% is treated, and of that TW, only 2–15% is reused for irrigation depending on region. The main limitation of TW for irrigation is the inability of current treatment technologies to completely remove all micropollutants and contaminants of emerging concern, some of which have unknown impacts on crops, environment and health. However, advanced water treatment and reuse schemes, supported by water quality monitoring and regulations, can provide a stable water supply for agricultural production, as demonstrated in regions such as the USA and Israel. Such schemes could potentially serve a net energy source, as the embedded energy in wastewater exceeds treatment needs by 9 to 10 times. Agriculturally useful nutrients such as nitrogen, phosphorus and potassium could be also recovered and reused. TW reuse for irrigation could act as a major contributor to a circular economy and sustainable development, but the first steps will be funding and implementation of advanced and sustainable treatment technologies and social acceptance.

An upsurge in the study of antibiotic resistance in the environment has been observed in the last decade. Nowadays, it is becoming increasingly clear that urban wastewater is a key source of antibiotic resistance determinants, i.e. antibiotic-resistant bacteria and antibiotic resistance genes (ARB&ARGs). Urban wastewater reuse has arisen as an important component of water resources management in the European Union and worldwide to address prolonged water scarcity issues. Especially, biological wastewater treatment processes (i.e. conventional activated sludge), which are widely applied in urban wastewater treatment plants, have been shown to provide an ideal environment for the evolution and spread of antibiotic resistance. The ability of advanced chemical oxidation processes (AOPs), e.g. light-driven oxidation in the presence of H2O2, ozonation, homogeneous and heterogeneous photocatalysis, to inactivate ARB and remove ARGs in wastewater effluents has not been yet evaluated through a systematic and integrated approach. Consequently, this review seeks to provide an extensive and critical appraisal on the assessment of the efficiency of these processes in inactivating ARB and removing ARGs in wastewater effluents, based on recent available scientific literature. It tries to elucidate how the key operating conditions may affect the process efficiency, while pinpointing potential areas for further research and major knowledge gaps which need to be addressed. Also, this review aims at shedding light on the main oxidative damage pathways involved in the inactivation of ARB and removal of ARGs by these processes. In general, the lack and/or heterogeneity of the available scientific data, as well as the different methodological approaches applied in the various studies, make difficult the accurate evaluation of the efficiency of the processes applied. Besides the operating conditions, the variable behavior observed by the various examined genetic constituents of the microbial community, may be directed by the process distinct oxidative damage mechanisms in place during the application of each treatment technology. For example, it was shown in various studies that the majority of cellular damage by advanced chemical oxidation may be on cell wall and membrane structures of the targeted bacteria, leaving the internal components of the cells relatively intact/able to repair damage. As a result, further in-depth mechanistic studies are required, to establish the optimum operating conditions under which oxidative mechanisms target internal cell components such as genetic material and ribosomal structures more intensively, thus conferring permanent damage and/or death and preventing potential post-treatment re-growth.