Characteristics and removal of organic micropollutants in reverse osmosis concentrate from urban wastewater treatment plants: A review

The use of reverse osmosis (RO) in urban wastewater treatment plants is becoming popular due to its efficiency in producing high-quality effluent suitable for various reuse applications. However, the process generates reverse osmosis concentrate (ROC) or reject as a byproduct, which poses significant environmental concerns. One of the primary issues with ROC is the presence of organic micropollutants (OMPs). These pollutants are found in substantial concentrations in reject water, raising concerns about their potential ecological and health impacts. This review provides a summary of the characteristics of ROC from urban wastewater treatment plants, focusing on the concentrations and types of OMPs present. The study shows that ROC contains a variety of dissolved organic compounds, dissolved ions, and organic micropollutants, making its treatment a challenge. The paper discusses various technologies studied for the removal of OMPs in ROC, including adsorption, advanced oxidation processes (AOPs), and other methods. Adsorption is identified as an effective method for the removal of OMPs, although some compounds show lower removal efficiencies. AOPs also have good removal capabilities but at the cost of forming potentially harmful byproducts. Emerging technologies such as forward osmosis combined with adsorption, constructed wetlands, and other microbial processes show promise but require further research for practicality. This paper thus underscores the necessity for continued innovation and optimization in ROC treatment methods to mitigate the adverse effects of OMPs on the environment and public health.