A global overview of treated wastewater guidelines and standards for agricultural reuse

Increasing demand for irrigation water leads to reuse treated wastewater as an alternative source, especially in countries facing water scarcity. Besides its benefits, wastewater reuse in irrigation may pose health and environmental risks if applied in an uncontrolled manner. There exist a number of wastewater reuse standards and guidelines for agricultural irrigation in various countries. In this study, available guidelines and standards were reviewed and classified according to microbiological parameters, metal concentrations in reused water, and irrigation water quality parameters. These are presented for various countries with the aim of providing an insight to authorities, institutions, and decision-makers. Upon investigation of the set values, it is seen that the quality limits differ from country to country, and that implementing a single standard seems to be difficult due to national and/ or local circumstances. In parallel to scientific evidence and technological advances, continuous improvement in revising/ expanding the existing standards and guidelines is expected. Besides, control and monitoring of efficient reuse applications along with training of the public should be encouraged.