Revisiting regulatory standards for treated wastewater utilization in edible crop irrigation

• Treated wastewater is a viable but risky option for irrigating edible crops. • Current reuse guidelines do not protect from emerging contaminants. • Advanced treatment technologies are imperative to ensure safe irrigation practices. • Source-screened low-pollutant effluents are preferable for edible-crop irrigation. The uncontrolled use of treated wastewater, particularly for edible crops, can cause adverse environmental and public health impacts. Consequently, several organizations have established standards for its reuse in edible crop irrigation. Regulations are increasingly being developed, with WHO providing guidance and agencies such as the USEPA offering frameworks many developed countries have adopted into binding regulations. Using the PRISMA framework, this study examined worldwide regulations and guidelines based on a structured selection of peer-reviewed literature and regulatory documents identified through systematic screening and inclusion criteria. The findings show that while developed economies have well-defined standards, many developing countries, particularly in Africa, either rely on international guidelines or lack formal regulations. Most existing standards focus on limited parameters, mainly BOD, COD, pathogens, and heavy metals, with little consideration of emerging contaminants, which are increasingly detected in treated wastewater and may accumulate in soils and edible crops, posing risks to human health and environmental systems. The study highlights challenges in wastewater treatment for reuse and the risks associated with irrigating edible crops. Treated wastewater with lighter pollutant loads, such as stormwater, rainwater, and domestic wastewater, can be prioritized because it requires less intensive treatment to meet safety standards. However, policies that incorporate emerging contaminants and promote advanced treatment technologies are needed to achieve Class A irrigation water, i.e., reclaimed water suitable for unrestricted irrigation under frameworks such as WHO and EU guidelines. These efforts support SDG 6, SDG 2, and SDG 12 by promoting safe water reuse, food security, and environmental sustainability.