Abstract
Population growth and water scarcity necessitate alternative agriculture practices, such as reusing wastewater for irrigation. Domestic wastewater has been used for irrigation for centuries in many historically low-income and arid countries and is becoming more widely used by high-income countries to augment water resources in an increasingly dry climate. Wastewater treatment processes are not fully effective in removing all contaminants, such as antimicrobial resistant bacteria (ARB) and antimicrobial resistance genes (ARGs). Literature reviews on the impact of wastewater irrigation on antimicrobial resistance (AMR) in the environment have been inconclusive and mostly focused on treated wastewater. We conducted the first systematic review to assess the impact of irrigation with both treated or untreated domestic wastewater on ARB and ARGs in soil and adjacent water bodies. We screened titles/abstracts of 3002 articles, out of which 41 were screened in full text and 26 were included in this review. Of these, thirteen investigated irrigation with untreated wastewater, and nine found a positive association with ARB/ARGs in soil. Out of thirteen studies focused on treated wastewater, six found a positive association with ARB/ARGs while six found mixed/negative associations. Our findings demonstrate that irrigation with untreated wastewater increases AMR in soil and call for precautionary action by field workers, their families, and consumers when untreated wastewater is used to irrigate crops. The effect of irrigation with treated wastewater was more variable among the studies included in our review, highlighting the need to better understand to what extent AMR is disseminated through this practice. Future research should assess factors that modify the effect of wastewater irrigation on AMR in soil, such as the degree and type of wastewater treatment, and the duration and intensity of irrigation, to inform guidelines on the reuse of wastewater for irrigation.
Highlights
Future research should investigate whether antimicrobial resistant bacteria (ARB)/antimicrobial resistance genes (ARGs) are detected in waters impacted by wastewater irrigation
Through a systematic review and synthesis of the available literature, we demonstrate the diverse impact that domestic wastewater irrigation can have on the presence of antimicrobial resistance (AMR) in soil
Our findings indicate a clear relationship between untreated wastewater irrigation and increasing prevalence and abundance of ARB and ARGs in soil
Summary
Consequences of an ever-growing global population, such as water pollution, climate change, and unevenly distributed water resources, have led to limitations in accessing clean freshwater, driving the need for the reuse and recycling of water resources. Agriculture is the largest user of freshwater and accounts for almost 75% of water use [1]. With the world’s population estimated to reach 10 billion within the 30 years, agricultural production is predicted to increase by 70%, putting further strain on freshwater resources [2]. Almost 50% of the world’s population uses polluted water sources for agricultural irrigation, and 20 million hectares are estimated to be irrigated with wastewaters [3]. Wastewater has been used in agriculture for centuries in many cities around the world that have a
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