Ecological Risk Assessment and Sustainable Management of Pollutants in Hydroponic Wastewater from Plant Factories

Although the plant factory (PF) industry is expanding worldwide, there are currently no regulatory measures for wastewater discharged from PFs in South Korea. This study aims to present the characteristics of major pollutants discharged from PFs that have not been reported in the literature and suggest effective management measures for them. The occurrence of 17 pollutants in hydroponic wastewater (HW) from 33 PFs was analyzed, and their potential ecological risk (PER) to aquatic life was assessed. Water samples were collected up to three times from each PF. The detection frequencies of 11 pollutants, including total organic carbon, total nitrogen, total phosphorus, Mn, Ni, B, Mo, Cr, Cu, Zn, and Ba, in HW exceeded 50%. Ni, Cr, and Ba are notably not recommended components of nutrient solutions in South Korea. Among the micropollutants, the concentration of Cu, which is a recommended component, was the highest, at 10.317 mg/L. The PER assessment identified Cu and Zn as “high-hazard” pollutants, with Cu, Zn, Ni, Mn, and B prioritized for management. To ensure the sustainability of hydroponic cultivation, these five pollutants must be managed. Nature-based techniques, such as the implementation of constructed wetlands and phyto-filtration, are recommended for effective treatment.