A Review of Reclaimed Water Use for Irrigation of Produce Crops and Food Safety Aspects in the United States

The global use of reclaimed (or recycled) water for irrigation in agriculture presents a sustainable solution to water scarcity and regional saltwater intrusion control by augmenting freshwater supplies. Reclaimed water typically consists of municipal wastewater effluent that has been treated with a combination of physical, biological, and/or chemical processes to a water quality that is consistent with the intended beneficial use. In the US and globally, the use of reclaimed water for certain food crop irrigation uses raises potential food safety concerns, in part because of the lack of federal regulations specific to the irrigation of produce (i.e., fruits and vegetables commonly consumed as raw) with reclaimed water. In the US, the consequent reliance on nonuniform state requirements complicated public health perspectives. Furthermore, there is still uncertainty related to the efficacy of wastewater treatment as it relates to constituents of emerging concerns (CECs), including pathogens such as Cyclospora cayetanensis, and the toxicological relevance of the ever-expanding and evolving list of chemical hazards. Collectively, these issues hinder the practical adoption of reclaimed water by interested agricultural stakeholders and provoke dissent by regional communities. This review aims to examine the current status of reclaimed water use for produce crop irrigation, focusing on state regulations, microbial criteria, operational characteristics, efficacy of treatment processes in mitigating microbial hazards, and associated studies evaluating the degree to which current reclaimed water standards adequately protect public health. Arguably, research is still needed to evaluate the efficacy of various treatment trains against the more recalcitrant pathogens, such as C. cayetanensis, and to understand when this hazard may pose potential contamination risks.