Reclaimed water for the irrigation of agricultural production is increasingly gaining attention, worldwide. However, the issue of the presence of chemical compounds in treated effluents is alarming the scientific community, as this poses concerns and challenges for both human health and the natural environment. More specifically, the persistence of chemical compound residues such as personal care products and pharmaceuticals in effluents, even after the end of the wastewater treatment process, may pose threats for human health, the surrounding soil, water resources as well as compromise drinking water resources. Once crops are exposed, there is potential transport and accumulation of the chemical compound residues to the edible part of fruits and vegetables as well as their roots and shoots.
To this end, for the limitation of exposure of humans and natural environments to such chemical hazards, more stringent quality requirements should be applied during agricultural irrigation. Despite successful implementation of various water reuse regulations and guidelines, there are still critical gaps in knowledge regarding the risks arising from chemical exposure and their address within the regulatory context (Helmecke et al., 2020). Thus, the introduction of a new water reuse regulation by the European Union is a good chance to address chemical risks in a sound and coherent manner. It is widely acknowledged that further guidance for the conduction of science-based risk assessment is needed for deriving the essential regulation measures. An adequate level of detail should be provided for the encouragement of a widely harmonized risk management approach and monitoring of appropriate indicator compounds, as well as consideration of available infrastructure, reclaimed water quality and desired water end uses (Helmecke et al., 2020).
In more detail, reducing the chemical compounds at the source, the optimized application of combinations of physicochemical and biological treatment processes for the removal of chemical residues as well as good agricultural practices and effective stakeholder communication are key elements of the assurance of safe agricultural irrigation.
Despite the need for stringent regulation and controls of treated effluents for water reuse, amidst a changing climate, water demand management, water saving efforts and reduction of water loss are of top priority in regard to irrigation techniques and overall water consumption.