Organic micro-contaminant sorption, transport, accumulation, and root uptake in the soil-plant continuum as a result of irrigation with treated wastewater

The use of treated effluents in agriculture for irrigation has become the mainstay in Israel and other parts of the world due to increasing population and the limited amount of high-quality water. While effluent irrigation has immediate benefits, such as mitigating water shortages and providing plant nutrients, the disadvantages and potential risks associated with its long-term use need to be evaluated if it is to be considered a sustainable practice. Among the potential risks associated with effluent irrigation is the presence of anthropogenic chemicals in the effluents (e. g., hormones, pharmaceuticals, and pesticides), enhanced transport of these chemicals out of the root zone due to their interaction with effluent-borne dissolved organic matter (DOM), and the possible uptake of these anthropogenic chemicals by plants and crops. DOM may reduce the sorption of organic pollutants through stable DOM-pollutant interactions in solution or by competing with the pollutant molecules for the sorption sites on the soil surface. The extent and nature of the interactions of dissolved organic matter with organic pollutants depend on factors such as the nature of the organic compound and the size, polarity, and molecular configuration of the DOM. In addition to the potential risks associated with effluent-borne DOM, contaminants present in treated wastewater may leach into groundwater used as a drinking water source or enter aquatic ecosystems through irrigation runoff. There are also concerns about whether these organic micro-contaminants can be taken up by plants and crops. A large number of potentially problematic organic micropollutants have been identified in treated wastewater and in streams receiving treated effluent. Classes of pollutants identified or potentially present in treated wastewater include pharmaceuticals, personal care product ingredients, nutraceuticals/herbal remedies, flame retardant chemicals, plasticizers, and disinfection byproducts. In this paper we review some of the potential risks posed by irrigation with treated effluent (wastewater), with a specific emphasis on organic chemicals present in the wastewater and soil-applied pesticides.